Site-wide links

Formulation FAQ

 

 

Do you have a question about color? Here is our current list of Frequently Asked Questions.

This page has been populated with questions submitted from around the world over the last decade. While we are no longer accepting new questions, we hope you enjoy reading the questions and answers here.

Other categories can be selected below:
Perception   |   Measurement   |   Imaging   |   Formulation   |   Color Order   |   Light & Matter

I project two spot lights on a white screen, RGB=(255,255,0) and RGB=(255,0,255), when both lights combine additively, what "color" I will see? Could I predict the mixture in the RGB Color Space?   (answer)

I am a Colorist, want to reduce validation work in laboratory. If I add a quantity of pigment and Tio2 paint, and then measure the shade, we get a certain CIELAB value. From that can I predict CIELAB values given a different quantity of pigment and TiO2?   (answer)

In textile color matching, Is it possible to match target color in all light source without metamerism. If so what will be the possibility percentage?   (answer)

How can I avoid metamerism?   (answer)

We are told that Red, Yellow, and Blue are the "primary" colors, and that you can make all other colors from them, but those 3 can´t be made by combining the others. In additive systems, it is red and green that combine to make yellow. Is there something inherently special about red, yellow, and blue, or are they considered "primary" only in the sense that the most basic medium of color manipulation is a subtractive system?   (answer)

I need to predict CIELAB of a color at different thickness. The color is transparent and .01 inches. How do I predict LAB values at thicknessof .121?   (answer)

What is the differance between additive color and subtractive color?   (answer)

I would like to convert from CIELAB coordinates into the approximate spectral red green and blue component curves. Is this possible?   (answer)

What dyes are mixed to get Dark Shell Gray?   (answer)

Are grey shades actually constant, because they are nearly achromatic, or is there something about eye biomechanics that create a visual perception not in agreement with spectral readings?   (answer)

Is it possible to determine the ink densities (or transmissivities) in a small area (~20 mm^2) of a four color image (CMYK) from its reflectance spectrum? The relative areas of coverage and overprint of the inks are not known. Illuminant and substrate spectra are available.   (answer)

Can you define what is Multiflux math model used in color mathing?   (answer)

How can I have someone create a paint for me using a theoretical spectral reflectance curve?   (answer)

Why is blue ink most commonly used for writing?   (answer)

What is the Kubelka Munk Theory? What its use in textile dyeing process? Would you please provide me any literature on the Kubelka Munk theory?   (answer)

I found a source that says an RGB of 194, 32, 11 for Calder Red. Can you tell me what proportions of red, yellow, and blue paint should be mixed to get that RGB?   (answer)

I want to make a slate grey color from white exterior latex paint. What additional colors and quantities of color will I need to mix?   (answer)

I am an artist interested in painting with photochromic inks or paints. Do you know of a supplier?   (answer)

What are the names of pigment suppliers who mfg or distribute metameric pigments?   (answer)

What mixture of acrylic painiting do I need to achieve a copper tone?   (answer)

Where can I find absorption or reflectance data for inorganic chemicals or pigments?   (answer)

Is pink a shade of red?   (answer)

Do you know of any freely available color matching software?   (answer)

Can you explain how detergents would cause color fading?   (answer)

I would like to make a children's computer program emulating colour mixing of paints. Since coputers generally use the RGB colour model, I don�t know how to achieve this. Can you help?   (answer)

Can you provide list of non toxic pigments that are insoluble in water measuring about 1 micron particle diameter?   (answer)

I require formulation for a Paint that absorbs magnetic rays or RF energy used by RADAR and do not reflect back.   (answer)

Is it possible for a liquid subtance to appear clear or colorless when placed on a white piece of paper with the naked eye, but will appear a unique color when seen through a filter?   (answer)

I am interested in obtaining a very accurate spectral match of my color sample. Some of the color matching systems I have used in various paint stores do a pretty good job of matching the color but not necessarily the spectrum of my sample.   (answer)

I am creating a colorant database for my matching software. How do I reduce the bronzing of Pth Blue at high concentrations?   (answer)

I am building a fiber glass airplane. The kit mfg says paint it any color you want as long as its white due to heat build up in the sun. Any idea of how far off-white I can get? How can I calculate the increase in heat absorbtion if I go a little blue or yellow off of white?   (answer)

How does one go about using use color measurements to determine the concentrations of colorants/dyes in aqueous solutions?   (answer)

How can I match a paint color to Munsell N8?   (answer)

Is there a source for a neutral gray paint designed to be used on floors and/or walls in a TV broadcast studio?   (answer)

I would like to find pigments with relatively narrow spectral aborption bands. The goal is to create paint which offsets the peak emission lines of different artifical light sources. Can you help?   (answer)

Out of blue, green or peach, which color is more likely to attract flies or insects and why?   (answer)

I'm looking for the paint formulation for the official colors of West Virginia University. The Pantone colors are either: A) PMS 873 metallic gold and PMS 295 Navy Blue or B) PMS 124 Gold and PMS 286 Blue. Can you help?   (answer)

In your opinion what pantone color best defines TEAL?   (answer)

At our paint-supply company we need to match a color to existing color on a clients' wall. Is there a portable instrument we can use to determine the required mix to match the exisitng paint?   (answer)

What do I tell the paint store to mix in order to get a color that best matches a wavelength (5040 Angstroms)?   (answer)

I have a thin PET film that is colored with dyes. I am suprised by the amount of dye required to match the opacity of the current film. Would you say that dyes are more linear than conventional pigments are when referring to thickness and saturation?   (answer)

How I can find the formulation of paint after coating?   (answer)

What are the colour combinations or chemical substances that can be used to obtain jet black colour in a cotton flannel material?   (answer)

Why is blue light plus yellow light equal white light, but blue and yellow paints mix to green? Why do the color wheels from various systems use different primaries?   (answer)

What is a full-spectrum paint and what is it good for?   (answer)

Are RAL 7032 and ANSI 61 are same colours? Where I can I locate a colour cross reference table between RAL & ANSI standards?   (answer)

What color will a solution that absorbs all the green, yellow and red light appear?   (answer)

Do you know the RAL Number for a cream colored paint known as Queen Ann or Magnolia?   (answer)

Should ideally conditioned standards (kept humidity controlled, dark envelope, minimum exposure to light, minimum handeling) develop metamerism?   (answer)

I am searching for paint color mixing recipes for liquid (bottle/jar) opaque water based pigment paints. I have found a book of colored paint mixing recipes for paste (tube) bodied paints with a volumetric proportioning system for only paste consistency (tube) paints: Color Mixing Recipes ; by Walter Foster Publishing Staff, (48 pages, Trade Paperback); 2005. Do you have any resources and/or pertinent leads that you could provide me?   (answer)

I painted a very pale yellow on one of my bedroom walls. I do not like the contrast with the country blue on the three other walls. Can I paint a brown that complements the blue over the yellow without affecting the brown color?   (answer)

I wish to have a white bedroom, where in the walls ceiling and floor are white. The windows doors and all wooden furniture will be painted white too. Kindly advise me on the suitability of the scheme. Should I be using stark white or would the use of ivory white be better. What should be the finish of the paint?   (answer)

My customers set up the upper limit of ΔE=1. This a very difficult to match, and I've got the information that the human eye can't detect a deviation below ΔE=2. Which would you recommend to set-up? Also, what is the grayscale-measurement for plastic parts?   (answer)

I've seen so-called UV energy beads change from white to various colors when exposed to UV light. What type of chemicals are embedded in those plastic beads, and are they toxic?   (answer)

What is the maximum opacity for 1 micron thick white ink? is there a theoretical calculation?   (answer)

I am working on matching a number of colours for plastic production. How do I convert my CIELAB values to colour pigments for production?   (answer)

I am looking for color matching software for matching translucent materials. Are there any commercial packages that employ multiflux theory to aid in prediction and correction of CIELAB values as well as contrast ratio in formulations?   (answer)

Regarding the use of Kubelka-Munk theory and reflectance values, if I used the spectral reflectances for the Macbeth Color Checker, how do I determine the K and S values needed for the calculation (if I want to used the two-constant theory)?   (answer)

A customer has asked for these colors: Light Green: 0.5G6.25/6.3 and 0.5G5.6/7.0 and 0.5G5.1/7.5, but I don't know how to translate it. He told me it's from Munsell and color is light green. How can I transfer to Pantone or NCS etc. to make a sample for him?   (answer)

Can I increase the opacity of a white Ink (at a given thickness) without affecting the color? I use TiO2. Are there other pigments that will increase opacity without affecting the whiteness index or CIELAB values?   (answer)

I do not have access to a spectrophotometer to measure paint reflectances. Where can I obtain the reflectance data for determining the Kubelka-Munk coefficients?   (answer)

What can you tell me about automotive paint pigments?   (answer)




I project two spot lights on a white screen, RGB=(255,255,0) and RGB=(255,0,255), when both lights combine additively, what "color" I will see? Could I predict the mixture in the RGB Color Space? (923)
Assuming you are viewing the spots in the dark and that they completely overlap (to avoid simultaneous contrast), then you will see a light pink color. You can predict the RGB mixture by adding the values to get 510,255,255. Since a single display can't typically output "510" you would have to scale them down to the max of 255 and the projected color will be dimmer than the mixture you describe. If the display was linear the scaled values are 255, 128, 128. However most displays are not linear so you would need a characterization of that nonlinearity (called gamma) to get the correct scaled down values. For most displays it would be something like 255, 189, 189 in order to get a dimmer version of your color. (Back to top)


I am a Colorist, want to reduce validation work in laboratory. If I add a quantity of pigment and Tio2 paint, and then measure the shade, we get a certain CIELAB value. From that can I predict CIELAB values given a different quantity of pigment and TiO2? (905)
There is no direct way to do this from the CIELAB coordinates. You would need to use a colorant formulation system along with a database to characterize your colorants and paint bases. Such a system would also allow you to predict mixtures of various colorants. (Back to top)


In textile color matching, Is it possible to match target color in all light source without metamerism. If so what will be the possibility percentage? (900)
It is possible, but only when the spectral reflectance of the match and the target are identical. This requires that the properties of the textile substrate be the same and that the same colorants are used in the target and the match. If those conditions are met, then the probability of a spectral match depends only on the control of the coloring process. If those conditions are not met, then the probability of a spectral match is difficult to predict, but it would be quite low. (Back to top)


How can I avoid metamerism? (891)
Metamerism cannot be avoided since it is really a property of the human visual system. Metamerism refers to the fact that two colors do not have to be identical in spectral power distribution in order to match in perceived color. You are probably thinking of illuminant metamerism in which two samples match for one light source (a metameric match in which the spectral reflectances differ) and do not match for another light source. The only way to avoid that is to produce spectral matches. (Sorry.) (Back to top)


We are told that Red, Yellow, and Blue are the "primary" colors, and that you can make all other colors from them, but those 3 can´t be made by combining the others. In additive systems, it is red and green that combine to make yellow. Is there something inherently special about red, yellow, and blue, or are they considered "primary" only in the sense that the most basic medium of color manipulation is a subtractive system? (888)
They are but one set of subtractive primaries and red, green, and blue are the typical additive primaries. There is nothing special about them. Primaries are simply three lights (additive) or colorants (subtractive) that can make a range of colors and chosen such that none of them can be made by a mixture of the other two. (Back to top)


I need to predict CIELAB of a color at different thickness. The color is transparent and .01 inches. How do I predict LAB values at thicknessof .121? (874)
It can be done if you have the spectral transmittance data for your material. It cannot be done from the CIELAB values alone. You would basically want to use the Bouguer-Beer Law that relates the transmittance of a material to the colorant concentration (fixed in your case) and the thickness. In the simplest terms, for each doubling of thickness, you square the spectral transmittance. However, you should look at the details in a textbook such as Berns Principles of Color Technology, 3rd Ed. (pp. 157-161). This is sometimes referred to as simple subtractive mixing. (Back to top)


What is the differance between additive color and subtractive color? (864)
There is no difference in the colors themselves, the difference is in how they are produced. The following answers come from WhyIsColor:

Q: How does additive color mixing work?
A: Additive mixing happens when two or more light sources are superimposed by either illuminating the same spot or by being so close together in space and time that oure visual systems cannot distinguish them. What we perceive is the sum of the energy from each of the lights. This is how computer displays and televisions reproduce color. Red, green, and blue are common additive primaries since it is easy and efficient to makea wide variety of colors with them.

Q: How does subtractive color mixing work?
A: Subtractive mixing happens when two or more dyes or pigments are combined by either layering or mixing them. Each dye or pigment absorbs certain colors (wavelengths) and what we perceive is the light that remains after each colorant has absorbed its part. This is how some printing systems and paint mixtures produce various colors. Cyan, magenta, and yellow are common subtractive primaries since it is easy and efficient to makea wide variety of colors with them. (Back to top)


I would like to convert from CIELAB coordinates into the approximate spectral red green and blue component curves. Is this possible? (849)
It's not really possible since a given set of CIELAB coordinates can be produced by an essentially infinite variety of spectral power distributions. The only way this problem can be solved is to assume a limited form of the spectral curves and then compute mixtures of those properties. (Back to top)


What dyes are mixed to get Dark Shell Gray? (835)
I'm sorry but that's really impossible to answer for a couple of reasons. First, color names are generally not defined precisely so "dark shell gray" could be a wide range of colors. Second, the dyes used would depend on the type of materials being used to make the color and even within a single material type it is possible to make the same color with many different combinations of colorants. (Back to top)


Are grey shades actually constant, because they are nearly achromatic, or is there something about eye biomechanics that create a visual perception not in agreement with spectral readings? (825)
Grays, like any colors can be very color inconstant. It really depends on the combination of reflectance characteristics, light sources, and observers. The most likely samples to be nearly constant would be grays with flat reflectance curves (known as nonselective materials). However, even those are likely to not be perfectly color constant. (Back to top)


Is it possible to determine the ink densities (or transmissivities) in a small area (~20 mm^2) of a four color image (CMYK) from its reflectance spectrum? The relative areas of coverage and overprint of the inks are not known. Illuminant and substrate spectra are available. (813)
Yes it is possible. However, in addition to the information you mentioned, you would also need to know the characteristics of the inks and their interaction with the substrate. Essentially, you need to have a model of the printing system and you could use that to determine the CMYK coverages needed to produce any given color. It is not a simple matter, but it is possible. (Back to top)


Can you define what is Multiflux math model used in color mathing? (789)
Here are a couple of suggested references from our faculty:

  • H. G. Völz, Industrial Color Testing: Fundamentals and Techniques, 2nd ed, Wiley-VCH, New York, 2001.
  • Articles by Willard Richards
(Back to top)


How can I have someone create a paint for me using a theoretical spectral reflectance curve? (783)
There are computer color matching systems that are capable of determining the best spectral match possible for a given paint medium and colorants. In any given paint system, there are limitations, but many spectra can be matched. The best advice is to find a manufacturer of the type of paint in which you are interested and send them the spectrum. They should be able to compute the best match they could make for you.

Hardware and paint stores have color matching systems that can be used to measure a sample and formulate a match. However, it is likely that such systems are aiming for color matches, which are not always spectral matches. That would be an easy way to get something close if you have a sample of what you are interested in producing. (Back to top)


Why is blue ink most commonly used for writing? (764)
As with many historical questions, there are probably many factors involved. This website gives some history on ink and suggests that blue ink was the first color developed after black. That probably goes a long way toward explaining its popularity. Also, the utility of ink is in its legibility (in most applications) and legibility comes from contrast. After black, blue would provide the most visual contrast on white (and light) papers and thus be the easiest of the non-black colors to read. Beyond that, blue has also traditionally been one of the most popular "favorite" colors. It is likely that all these factors, and more, combined to make blue ink popular for writing. (Back to top)


What is the Kubelka Munk Theory? What its use in textile dyeing process? Would you please provide me any literature on the Kubelka Munk theory? (745)
Kubelka-Munk theory represents a series of mathematical models that can be used to predict the spectral reflectance properties of materials from measured absorption and scattering characteristics of the medium and colorants. Predicting color matches in the textile industry is one application of the theory. Much has been published on Kubelka-Munk theory and computer colorant formulation (or color formulation). A good starting point is an introductory textbook on colorimetry such as Berns' "Principles of Color Technology, 3rd Ed.". (Back to top)


I found a source that says an RGB of 194, 32, 11 for Calder Red. Can you tell me what proportions of red, yellow, and blue paint should be mixed to get that RGB? (740)
Unfortunately not. Neither RGB, nor red-yellow-blue paint, are standardized specifications of color appearance. Both would have to be well calibrated and characterized to define a match. Your best bet is to find a sample of the color you are looking for and then experimentally mix the paint to make a visual match (or take the sample to a paint store for matching if you are interested in large amounts of paint). (Back to top)


I want to make a slate grey color from white exterior latex paint. What additional colors and quantities of color will I need to mix? (738)
You would need to mix in some black paint (or more simply some black colorant). The amount would depend on just how dark you think "slate gray" is. You would probably need to do some experimenting. I would also recommend mixing all the paint together to get consistent color. Since that would be one big vat of paint, it might be easier for you to go to a paint store and ask them to make a match for you. They could add colorant to each gallon in a consistent manner and convert that paint from white to gray for you. (Back to top)


I am an artist interested in painting with photochromic inks or paints. Do you know of a supplier? (736)
I don't know of any specific vendors, but a search seems to suggest that some are available. See this Google search. (Back to top)


What are the names of pigment suppliers who mfg or distribute metameric pigments? (723)
They all do! Metamerism is not a property of individual pigments, but a property of pairs of color samples (they match under certain viewing conditions despite spectral differences). You can make them out of all sorts of colorants. (Back to top)


What mixture of acrylic painiting do I need to achieve a copper tone? (717)
The appearance of metallic objects, like copper, depends not only on the diffuse color, but the color of the highlights. Metals look like metals because their highlights are colored. That means that you can't directly mix a non-metallic paint to have the same appearance as copper. You would need to have a reddish-brown color and then paint a representation of a 3D object that illustrated the metallic highlights. In that sense you could mimic the appearance of a metal. (Back to top)


Where can I find absorption or reflectance data for inorganic chemicals or pigments? (703)
Sorry, I don't know of any specific source for such information. The best I can suggest is contacting some of the pigment manufacturers to see if they have data they can share or suggestions about where typical data can be found. You might also inquire with these folks. I'm not sure if they include spectral data or not. (Back to top)


Is pink a shade of red? (677)
Generally "shades" are colors produced by adding black to the color and "tints" are those obtained by adding white (in a subtractive system like paint). Thus, pink would be considered a "tint" of red and not a "shade". See practicalpainting.com (Back to top)


Do you know of any freely available color matching software? (662)
I am not aware of any free formulation software. The website matchmycolor.com does provide an inexpensive subcription solution. Other than that, you can obtain "free" software from many of the instrument manufacturers when you purchase an instrument. (Back to top)


Can you explain how detergents would cause color fading? (644)
Fading from detergents can happen in several ways, but the most likely causes are simply that the detergents are removing the colorants (chemicals producing the color stimulus) from the material or that the detergents are facilitating a chemical reaction that changes the colorants into a form that is colorless. (Back to top)


I would like to make a children's computer program emulating colour mixing of paints. Since coputers generally use the RGB colour model, I don�t know how to achieve this. Can you help? (641)
The technical details of paint mixing are quite complex, but you can make an approximation with simple subtractive mixing. The trick will be to convert from the subtractive model for paints to the additive model for your computer program. What you need to do is abstract the color combinations in the subtractive model and then convert the result to RGB. For example your "blue" paint is generally really a cyan color (G + B to display it) and yellow is G + R. If you did additive mixing of lights, then the result would be R + 2G + B (just add up the values). However, a subtractive mixture behaves differently. You have to look at the light that is missing. The cyan has removed the R and the yellow has removed the B, so starting with white (R + G + B) and removing those amounts you end up with (R+G+B) - B - R = G (the green you are looking for). You then have to factor in various amounts of these mixtures.

I hope that is helpful. There are also some demos at the SDC Colour Museum website. You have to click on the little floating icon to get to the demo. (Back to top)


Can you provide list of non toxic pigments that are insoluble in water measuring about 1 micron particle diameter? (629)
The definitive list of dyes and pigments (colorants) and their properties is the "Colour Index International". (Back to top)


I require formulation for a Paint that absorbs magnetic rays or RF energy used by RADAR and do not reflect back. (622)
This is not really a color question since absorbing radar and producing color happen at different wavelengths and they need not be related. There is a description of radar-absorbing materials here. (Back to top)


Is it possible for a liquid subtance to appear clear or colorless when placed on a white piece of paper with the naked eye, but will appear a unique color when seen through a filter? (621)
The only way to do this would be if the substance was opaque (like the paper) and had a spectral reflectance curve metameric to the paper for the first viewing condition, but not metameric when viewed through the filter. (Back to top)


I am interested in obtaining a very accurate spectral match of my color sample. Some of the color matching systems I have used in various paint stores do a pretty good job of matching the color but not necessarily the spectrum of my sample. (620)
Many, if not all, of the commercial color matching software packages (such as what you find in paint stores) use some form of spectral matching algorithm and such algorithms can be quite effective. However, the only way to get accurate spectral matches is generally to use the same material and colorants as the original. For example, if you were to match house paint with one of the systems in a paint store, you would have a good chance of getting a spectral match. In many cases you don't have the luxury of using the same materials and colorants so you have to settle for a colorimetric match (probably metameric). (Back to top)


I am creating a colorant database for my matching software. How do I reduce the bronzing of Pth Blue at high concentrations? (614)
The usual cause of this is that you have reached too high a concentration of colorant for your substrate and it is coming to the surface. Since this is happening, you are perhaps trying to construct your database at levels of concentration that will not be usable in your final products. You might well be able to build a usable database without going to such high concentrations. (Back to top)


I am building a fiber glass airplane. The kit mfg says paint it any color you want as long as its white due to heat build up in the sun. Any idea of how far off-white I can get? How can I calculate the increase in heat absorbtion if I go a little blue or yellow off of white? (610)
This is not a simple question to answer since it depends on more than just the color. Heat build up will come from light absorption (color), but also from absorption of ultraviolet and infrared radiation (which might have little correlation with color). So the answer can't be given simply in terms of color. However, if you select a paint that is a fairly light shade (near white) as you suggest, then it's properties in the UV and IR are likely to be similar to those of the same type of white paint. That is because there simply is not that much colorant in the paint to make a change at any wavelength. (Back to top)


How does one go about using use color measurements to determine the concentrations of colorants/dyes in aqueous solutions? (593)
This is essentially the topic of the area known as color, or colorant, formulation. The relationship between colorant concentration and spectral transmittance (in this case) is characterized for all colorants of interest and then an appropriate model (the Beer-Lambert Law in this case) is used to predict the characteristics of mixtures. Given a mixture of known colorants (unknown concentrations), it is possible to figure out the concentrations by inverting the model. Berns' text, "Principals of Color Technology, 3rd. Ed." provides a good overview of these procedures. (Back to top)


How can I match a paint color to Munsell N8? (570)
You could purchase a Munsell N8 sample from GretagMacbeth and then take that to a paint store to be matched. This is usually very effective and accurate. Alternatively, if the store can match a numerical specification, Munsell N8 translates into CIELAB values of L=80, a*=0, and b*=0 under daylight. You might be able to provide these numbers to the paint matcher and they could enter them into their system to formulate the match. (Back to top)


Is there a source for a neutral gray paint designed to be used on floors and/or walls in a TV broadcast studio? (568)
I am not aware of a specific standard or source for gray paint for TV studios. If you take a sample of the desired gray to a reputable paint store, they can measure it and produce a very close match. In your situation, and 18% photographic gray card might be a good choice to match. That is a bit darker than typical viewing booths, but I would think a slightly darker surround would be good in a TV studio. (Back to top)


I would like to find pigments with relatively narrow spectral aborption bands. The goal is to create paint which offsets the peak emission lines of different artifical light sources. Can you help? (567)
I've never come across such pigments. In general it is difficult to produce such narrow absorption bands with the exception of some materials like rare earth metals. This is really a chemistry question and I am not sure who can best answer it. There is a department of colour chemistry at the University of Leeds. Perhaps someone there can point you in the right direction. (Back to top)


Out of blue, green or peach, which color is more likely to attract flies or insects and why? (560)
I don't know of detailed research myself. But I did a google search on the terms color, attraction, insects, and found quite a few pages of interest. This one (scroll down to the color part), suggests that the attractive colors vary by type of insect. (Back to top)


I'm looking for the paint formulation for the official colors of West Virginia University. The Pantone colors are either: A) PMS 873 metallic gold and PMS 295 Navy Blue or B) PMS 124 Gold and PMS 286 Blue. Can you help? (555)
Since it sounds like the color matching system that the paint formulator has is not capable of matching Pantone colors directly (that would require the system developer to have licensed the Pantone system), the next best solution would be to use a Pantone book and have the formulator measure the two color patches on their spectrophotometer in order to formulate a match. If your formulator can't do that, go to another one. Most hardware stores have a spectrophotometer available to allow matching to customer samples. Go Mountaineers!!! (Back to top)


In your opinion what pantone color best defines TEAL? (554)
The only opinion that matters is yours, or your customer's. The best thing to do is look through a set of Pantone samples and select the one that best represents teal to you. Color names are not generally used that consistently and there is usually no scientific way to pinpoint the best example. (Back to top)


At our paint-supply company we need to match a color to existing color on a clients' wall. Is there a portable instrument we can use to determine the required mix to match the exisitng paint? (549)
Yes. Most, if not all, of the instrument manufacturers make portable hand-held spectrophotometers that could make the necessary measurements. You would then need to match those measurements with your existing paints or use your current colorant formulation system to predict the paint recipe. If you currently have a non-portable system that does this job, then you should be able to use the colorimetric values measured on the portable system with your current software to predict a match. The instrument manufacturers should be able to help you put together an appropriate system. (Back to top)


What do I tell the paint store to mix in order to get a color that best matches a wavelength (5040 Angstroms)? (544)
You really can't make paint that is a perfect match to light of a single wavelength. In this case, the wavelength you selected (5040 Angstroms or 504 nm) would appear cyan, or bluish-green, if viewed in isolation. Since paint doesn't reflect just a single wavelength, you can't reproduce this physical stimulus with paint. Even if you could, it would be very dark since it would be absorbing most of the visible spectrum. The best you can do is make a visual approximation. For this wavelength, you could go to the paint store and select the paint sample that is bluish-green (about half way between an ideal green and ideal blue) and as bright and chromatic (saturated) as possible. (Back to top)


I have a thin PET film that is colored with dyes. I am suprised by the amount of dye required to match the opacity of the current film. Would you say that dyes are more linear than conventional pigments are when referring to thickness and saturation? (541)
I don't know that I would say more linear, but in general dyes do behave differently from pigments. In general, dyes are more transparent and pigments more scattering. Thus, if you are trying to make something opaque, you will have more difficulty with dyes unless the substrate itself is opaque. (Back to top)


How I can find the formulation of paint after coating? (514)
This is the process that a colorant formulation system performs. Based on the measurement of spectral reflectance of a sample, and a database of possible colorants, the system computes the best selection of colorants and the required concentrations to produce a match. If the colorants in the sample are already known, then such systems can do an even better job of predicting the required concentrations. Berns' text "Principles of Color Technology, 3rd Ed." provides an introduction to how this works and the various instrument manufacturers provide software solutions. (Back to top)


What are the colour combinations or chemical substances that can be used to obtain jet black colour in a cotton flannel material? (499)
I'm afraid specific colorant formulations are somewhat outside the expertise of our laboratory. However, given that cotton flannel tends to have a very diffuse surface, it will be difficult to achieve an extremely dark black. This is because the material surface is always scattering some light in all directions. (Back to top)


Why is blue light plus yellow light equal white light, but blue and yellow paints mix to green? Why do the color wheels from various systems use different primaries? (492)
Yellow and blue light mix together via additive color mixing to make white light since the yellow light is missing blue wavelengths that are filled in by the added blue light. Subtractive mixing of yellow (which removes the blue light) and cyan (which removes the red light) results in green. A subtractive mixture of a true yellow (removes blue) and blue (removes red and green) would result in black.

The term "primary" is used differently in different systems. For example, Munsell and NCS don't actually use the term at all. Munsell has principle hues and NCS uses the unique hues. Since primary can mean different things in different systems, the term needs to be interpreted carefully. The best generic definition is that of a "set of primaries" such that no one of the primaries can be made by mixing the other two. (Back to top)


What is a full-spectrum paint and what is it good for? (443)
The term "full-spectrum paint" makes no technical sense, but an internet search turned up some paints being marketed with this term. Apparently full-spectrum paint is paint in which no black pigments are used to create the final color mixture. A given paint color could be formulated from a mixture of white, black, and one or two chromatic pigments or from a mixture of several chromatic pigments with white. This later mixture is what is being marketed as "full-spectrum" paint. There is probably little practical difference between the two methods for producing a given color. However, the paints would most likely have different spectral reflectance properties (neither is more "full" than the other) that would make them behave differently when the color of the illumination is changed or when the paint reflects upon itself (as in the corner of a room). These differences are likely to be very subtle and go unnoticed by most people. It's just a different way to formulate certain colors and full-spectrum paint is good for the same things as regular paint, making our interiors more interesting and enjoyable (or not). (Back to top)


Are RAL 7032 and ANSI 61 are same colours? Where I can I locate a colour cross reference table between RAL & ANSI standards? (406)
The ANSI colors are defined by Munsell notations and standards that are available from GretagMacbeth (see gretagmacbethstore.com) and I am not aware of any direct conversion between those designations and the RAL numbers. Unfortunately all I can suggest is an inquiry to GretagMacbeth. Perhaps they can help you sort this out. (Back to top)


What color will a solution that absorbs all the green, yellow and red light appear? (397)
The simple answer is blue. The more complex answer is that appearance will also depend on the lighting and other viewing conditions. However, simply looking at subtractive color mixing, if you have absorbed all the green light and all the red light, then you are left with blue (generally people divide the yellow into the green and red regions, but since you said that was all absorbed as well, the answer wouldn't change). (Back to top)


Do you know the RAL Number for a cream colored paint known as Queen Ann or Magnolia? (395)
No, I don't. Color names are a very imprecise description. The best I could recommend is to find a sample that closely matches what you are looking for and then take that to your paint dealer and ask it to be matched. (Back to top)


Should ideally conditioned standards (kept humidity controlled, dark envelope, minimum exposure to light, minimum handeling) develop metamerism? (382)
I've never heard of cases of metamerism developing over time, but there is no fundamental reason that it wouldn't be possible. If two samples were colored with different colorants, it is feasible that the colorants in one could change over time differently from the colorants in the other. That could result in more significant metamerism. However, if both were made of the same colorants, then one changing should only result in a simple color mismatch (one changed, one didn't) and not metamerism.

How long samples last in a controlled environment is really impossible to say since it depends both on the material and the colorants. Again, I wouldn't expect metamerism to develop where none existed before, but the magnitude might change over time. (Back to top)


I am searching for paint color mixing recipes for liquid (bottle/jar) opaque water based pigment paints. I have found a book of colored paint mixing recipes for paste (tube) bodied paints with a volumetric proportioning system for only paste consistency (tube) paints: Color Mixing Recipes ; by Walter Foster Publishing Staff, (48 pages, Trade Paperback); 2005. Do you have any resources and/or pertinent leads that you could provide me? (374)
I have asked a number of people and found no good answer to your question. We are not aware of any books of paint recipes that would solve your two problems. I'm sorry I can't be of more help. (Back to top)


I painted a very pale yellow on one of my bedroom walls. I do not like the contrast with the country blue on the three other walls. Can I paint a brown that complements the blue over the yellow without affecting the brown color? (358)
Most home paint is nearly opaque so it should be no problem. Some light colors do show through, but that can usually be fixed by painting a second or third coat. Since the paint is designed to be as opaque as possible, the intent is that the color underneath would have no effect. Brown, being darker than the yellow should have no problems. (Back to top)


I wish to have a white bedroom, where in the walls ceiling and floor are white. The windows doors and all wooden furniture will be painted white too. Kindly advise me on the suitability of the scheme. Should I be using stark white or would the use of ivory white be better. What should be the finish of the paint? (357)
I won't ask you why you want to do this. It is pretty well established that we are more comfortable and relaxed in an environment with some visual contrast. You are proposing to remove as much of that contrast as possible. It probably won't be a pleasant room to be in. Of course, if you are asleep it won't matter. I don't think it matters at all what white you use and would advise simply choosing what you prefer.

An interesting note, if the room was completely uniform, it wouldn''t matter what color you chose since it would disappear from your perception anyway. Our visual system cannot perceive color where there is no spatial contrast (no edges) and everything quickly fades to a middle gray. You might do some reading on the Ganzfeld or Troxler fading to learn more about that. (Back to top)


My customers set up the upper limit of ΔE=1. This a very difficult to match, and I've got the information that the human eye can't detect a deviation below ΔE=2. Which would you recommend to set-up? Also, what is the grayscale-measurement for plastic parts? (350)
You are correct that a ΔE of 1.0 is a very tight tolerance. Unfortunately there is no easy answer to your question. The size of a perceptible color difference depends on the particular configuration of viewing and the color in question (not to mention the particular color difference equation used). You really need to establish a tolerance that is agreeable to both you and your customer. I don't blame them for saying 1.0 because they are sure to get what they want, but I would bet they would be happy (in many cases) with a less stringent tolerance. Berns' text, "Principles of Color Technology, 3rd Ed." provides more details on establishing visual tolerances.

I have never heard of "greyscale-measurement", but I would suspect it is just referring to the lightness dimension in CIELAB. In other words the L* value and its tolerance. (Back to top)


I've seen so-called UV energy beads change from white to various colors when exposed to UV light. What type of chemicals are embedded in those plastic beads, and are they toxic? (346)
The colorants imbedded in the beads are known as "photochromic colorants". A web search on that term will turn up lots of information on them. I couldn't find details on toxicity, but the colorants themselves are embedded in plastic prior to use, so they are probably not readily accessible. However, I would encourage you to be careful with these as you would with any man-made chemical. In other words, I wouldn't eat them! This web page gives a good overview of how photochromic colorants work (scroll down to the section on photochromic colorants near the bottom) and lists what some of the specific chemicals are. You could do some toxicity searches on those chemicals. Another page, gives some more specifics and explains how different colors are made. (Back to top)


What is the maximum opacity for 1 micron thick white ink? is there a theoretical calculation? (314)
The best method to explore questions like this is to study and apply Kubelka-Munk Theory. A good reference to explore is "Industrial Color Testing: Fundamentals and Techniques" by Hans G. Völz. (reference 4 at the bottom of this page) (Back to top)


I am working on matching a number of colours for plastic production. How do I convert my CIELAB values to colour pigments for production? (307)
There is an entire field known as colorant formulation that addresses the question you have asked. Essentially colorant formulation software takes the desired CIELAB values (or spectral reflectance curve) for your standard and uses information about your available pigments and mixing system to predict the required pigment amounts to formulate a match. Companies that sell spectrophotometers typically also sell color formulation software. You might check with companies such as Hunterlab, BYK-Gardner, Datacolor International, GretagMacbeth, etc. to learn about their products. You might also look at Berns' book, Principles of Color Technology to learn more about the process. (Back to top)


I am looking for color matching software for matching translucent materials. Are there any commercial packages that employ multiflux theory to aid in prediction and correction of CIELAB values as well as contrast ratio in formulations? (284)
I am not very familiar with all the technical specifications of the available commercial color formulation software. Many of the details are kept proprietary for competitive reasons. You would need to inquire with the manufacturers to find out if their software is applicable to your application. I believe that a previous package from X-Rite used multiflux theory and the webpage on their current formulation software mentions matching for translucent materials www.xrite.com. There are not many details on their page, but it might be worth an inquiry to see if their software, or that from other manufacturers, can be of use.

UPDATE: From a colleague at Benjamin Moore ...
"We do use our own, but I believe Xrite ColorMaster and GretagMacbeth Propalette are both multiflux color matching systems." By "our own" he means matching software they wrote in house. (Back to top)


Regarding the use of Kubelka-Munk theory and reflectance values, if I used the spectral reflectances for the Macbeth Color Checker, how do I determine the K and S values needed for the calculation (if I want to used the two-constant theory)? (259)
It is not possible to compute separate K and S constants for a single sample. Instead you need to have samples with several different concentration levels of the pigments involved in order to figure out the K and S constants. You can convert a single reflectance factor measurement into a (K/S) value using the normal equation for single-constant theory.

(K/S) = ((1-R)^2)/2R

There is more detail on this and further references in Berns' Principles of Color Technology, 3rd Ed. chapter 8. (Back to top)


A customer has asked for these colors: Light Green: 0.5G6.25/6.3 and 0.5G5.6/7.0 and 0.5G5.1/7.5, but I don't know how to translate it. He told me it's from Munsell and color is light green. How can I transfer to Pantone or NCS etc. to make a sample for him? (257)
Those are Munsell designations for various greenish colors. You can download free software from GretagMacbeth to convert from Munsell designations into a variety of color spaces. It does not include Pantone or NCS conversions. Pantone does not publish conversions to colorimetric spaces. I am not sure if an NCS conversion is available since their website is not working as I write this. However, you might be able to work with the CIE XYZ or CIELAB values from your the Munsell software to formulate your plastic pellets. (Back to top)


Can I increase the opacity of a white Ink (at a given thickness) without affecting the color? I use TiO2. Are there other pigments that will increase opacity without affecting the whiteness index or CIELAB values? (256)
First of all, you can't really increase opacity without changing the color. Opacity, by definition, affects color since more or less of the substrate is showing through. Presumably you were referring to not changing the color of the ink (i.e., keeping it white). To my knowledge, TiO2 has, by far, the largest refractive index of these pigments. As such, it would be the best scatterer (and therefore produce the most opacity). All the others are much poorer, especially when mixed with clear ink. Another possibility might be zinc oxide. There are also synthetic scatterers that are polymer beads. Perhaps they can be mixed to provide a good result. Yes, there are optimal pigment/volume ratios and it would probably require some experimentation with your particular inks to determine the best for your application. Pages 8-10 in Berns' book, Principles of Color Technology, 3rd Ed. have some introductory material about scattering. A more detailed reference that might be of value is "Industrial Color Testing 2nd Ed." by Völz. It includes a lot of material on scattering and particle size. (Back to top)


I do not have access to a spectrophotometer to measure paint reflectances. Where can I obtain the reflectance data for determining the Kubelka-Munk coefficients? (239)
This is a difficult question. If you are interested in just working with the Kubelka-Munk theory in general then you can essentially make up reflectance values to use in your code. Another alternative would be to search the internet for reflectance databases. For example, our website www.cis.rit.edu/mcsl/online/cie.php has spectral reflectances for the Macbeth Color Checker. Unfortunately those sources won't give you information about colorants at various concentrations that you would need to rigorously test a Kubelka-Munk implementation. If you are interested in a specific system (like a brand of paints), you might try making a request to the manufacturer for some nominal spectral reflectance data. Another alternative is to look for specification sheets from colorant manufacturers, who sometimes include reflectance data. Unfortunately, the only way to truly build and test a colorant formulation system is to have ready access to a spectrophotometer of your own. You might also refer to this web page regarding textile dying www.techexchange.com/thelibrary/colormatching.html. (Back to top)


What can you tell me about automotive paint pigments? (228)
MCSL doesn't do too much work on the actual formulation of pigments and other colorants. However, we do a lot of research on the use of colorants in various applications and the perception of the resulting colored materials. As you suggest, there are a wide variety of materials used as colorants in the automotive industry ranging from simple inorganic compounds to complex pearlescent or metallic "effects" colorants. To get more information on specific colorants and applications it is probably best to contact pigment manufacturers directly. A first step might be the Color Pigments Manufacturers Association. Also automotive paint manufacturers provide some information on their processes. For example, some can be found at DuPont Automotive. Also, a couple of books you might look at are "High Performance Pigments" by Smith and "The Pigment Handbook" by Lewis. The ultimate reference for all types of colorants is the "Colour Index International." (Back to top)


References

  1. G. Wyszecki and W.S. Stiles, Color Science: Concepts and Methods, Quantitative Data and Formulae 2nd Ed., Wiley, New York, 1982.
  2. R.W.G. Hunt, Measuring Colour 3rd Ed., Fountain Press, England, 1998.
  3. R.M. Boynton, Human Color Vision, Special Limited Edition, Optical Society of America, Washington D.C., 1992.
  4. M.D. Fairchild, Color Appearance Models Addison-Wesley, Reading, Massachusetts, 1998.
  5. R.S. Berns, Billmeyer and Saltzmann's Principles of Color Technology, Wiley, New York, NY, 2000. (from Wiley)
  6. H.G. Völz, Industrial Color Testing 2nd Ed., Wiley-VCH, Weinheim Germany, 2001.
  7. There are several links to GretagMacbeth's Color Conversion Freeware