#90 - Metamerism – Part 1

“Metamerism” is primarily a chemistry term for a type of isomerism in which chemical compounds have the same molecular weight and identical proportions of the same elements, but have different chemical properties because of radicals of different types or in different positions. Sounds complicated, but it’s basically a reference to two chemicals that you would expect to behave the same, but don’t because of minor differences.

In the coatings industry, especially in pigmentary studies, metamerism has a somewhat different meaning, but the idea is still sort of the same. Metamerism is a term used for when two colored samples appear to match under one set of lighting and viewing conditions, but not under another set. Metameric dissimilarity may also be due to differences in observers’ color perception aside from lighting or viewing conditions.

There are instruments available that simulate
various lighting and viewing conditions to
help manage unexpected metameric effects.

I have noticed that metameric effects are often more pronounced in coating systems that do not have high opacity and where the substrate is colored (non-white), or where the system is comprised of multiple layers of varying color contribution. Coatings that incorporate different types of coloring material types also seem prone to metamerism (e.g. organic/inorganic colorants or dyes/universal colorants added post-manufacture).

An example scenario might be a manufactured article whose color is designed and agreed to under the viewing conditions at the manufacturing facility, but doesn’t match expectations when the article is completed and moved to the final location. Metamerism may be the reason. (I say ‘may be’ because a legitimate manufacturing error may also be the cause.) During my time in the coatings industry, I dealt with metamerism often enough to appreciate its potential for disruption.

At Nova, we are thankful that we do not have to worry about such aesthetic complexities in our manufacturing process. Making gas analyzers is complicated enough already. But there are a couple of phenomena in gas analysis that remind me a little of metamerism. I’ll talk about those next time.

The Nova blog appears to be about gas analyzers, and yet this post discussed a completely different subject. Literary metamerism.

For information on these and other gas analyzer systems, give Mike or Dave at Nova a call, or send us an e-mail.
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