Metamerism is one of the most commonly-seen issues in textile dyeing. What is it, and can it be prevented?
natific’s expert engineer, Franziskus Haussinger, helps mills navigate this problem every day. He gave us some great information to share with our network.
What is metamerism?
In simple terms, metamerism is the effect of 2 samples matching each other under one light source, but when viewed under a different light source, the color appears to be changed. In the image below, we see a shirt with all components matching each other (and the standard) in daylight, but when the light source is changed, one component looks different.
The reason for this effect is the difference in light intensity. The different intensity of another light source leads to different excitations of the color molecules and peak in different wavelengths that our eyes are able to perceive!
Colors more sensitive to metamerism include purple, turquoise, red and green shades. Metamerism is also common when, for example, the standard is a cotton fabric and the desired color needs to be dyed on PES or Nylon.
Get metamerism under control:
When a mill is facing a metamerism issue, they have 3 ways to try to overcome it:
1. Change dye selection to achieve the color.
2. Add a 4th or even 5th dye to the ternary that they are using
3. Depending on how strong the flare is, adjust the shade in a way huewise to decrease metameric effect under a different light source. For example, a color flares red under secondary light source. The mill should adjust this color more to the greener sider (but still stay within tolerance) under the primary.
There are some cases, however, that are very difficult to correct even with these 3 solutions.
natific’s technical team has years of experience and one of the most valued services we offer clients is metamerism support. If a mill is having trouble, we provide the best possible recipes to overcome metamerism issues. We also give advice on shade adjustment to provide better metameric control.
Here’s some advice on how to avoid metamerism from the start:
A mill should first check their sample’s metameric behavior by confirming the ternary’s behavior under 3 different light sources, including A light. A light is especially important because one will be able to see if the ternary has a tendency towards metamerism. It is also important to check the CMCCON (color inconstancy index) value in their Datacolor Tools or X-Rite IQC software.
Additionally, natific has developed our own metameric index, the nMI (natific metamerism index) and it can be used by mills that are already operating with natific’s QcExpress software. The lower the number the lower the susceptibility for metameric issues.
nOSC: natific Optimized Spectral Curve
Mills should look out for any nOSC standards provided by their clients. These are optimized spectral curves that have been optimized in terms of color constancy, feasibility and dyeability. Such standards will provide a far higher safety when comes to meeting metameric issues!
Benefits for mills:
– Easier and faster shade development
– Fewer metamerism issues when changing one color on different fabrics
– The use of standard ternaries/ dyestuffs is possible in many cases
– Easier to meet fastness requirements
Benefits for brands:
– Far fewer FSRR, BCD and exceptional color approvals
– Better and more efficient fabric and color management over whole range of fabrics
– Shorter lead times due to feasible colors up front
Summary
Although metamerism is a common issue, it doesn’t have to be a big headache. With proper dye selection and adjustments, it can be kept under control. nOSC standards provide brands and mills the confidence to achieve feasible, non-metameric colors (we’ll talk more about this in the next newsletter). natific offers support to mills that face metameric issues – reach out to us at support@natific.com