Colorants

The Crazy and Confusing World of Colorants

Dyes, alcohol inks, paints, mica powders, other pigments - even metal powders used for cold castings (not to mention the chemicals used to give that a patina)... these are just some of the most common things used to bring that your casts to life with each colorful shot and it can get confusing quickly.

There are a ton of different facets you could get into (like certain colors tending to be more colorfast than others!) but for now lets focus on the distinction between pigments and dyes. And remember most of the things mentioned here are generalizations and there's probably an exception for each of the "rules".

By and large, pigments tend to be more colorfast and opaque and UV resistant than dyes, pigments also sometimes have issues staying dispersed in the liquid so you may see some settling both in their bottles which need to be shaken first as well as potentially in your casts if you're using a slow curing resin especially with heavier pigments. Generally that would probably only be the ones you buy as actual powder not things like UVO and even then not always an issue to worry about...

Another consideration is the fact that adding liquids to your resin can affect the cure of your resin as well as the physical properties after it cures - especially for urethane resins but somewhat for epoxy too. Most powdered colorants you encounter would be classified as pigments (though there are powdered dyes they're much less commonly used for keycap making - I've used some to dye wood and fabric planned for micarta but haven't encountered anyone using it for caps beyond that... yet). Liquid colorants on the other hand can be either dyes or pigments - for example Smooth-on's UVO line is pigment based whereas the So-Strong line is dyes (actually I'm second guessing that now because they call them "tints"? but at least part of Alumilite's line is dyes)

While it is important to consider how the liquid will affect your resin, a lot of the things that make it important to distinguish between liquid dyes vs liquid pigments in other applications don't matter as much for resin as they would elsewhere. Pigments for example tend to sit more on the surface where as dyes penetrate more - which is important for things like wood stabilization I've been told some Alumilite's liquid colorants don't work for wood stabilization because the particles are too big and they don't penetrate beneath the surface which makes me suspect they are actually pigment based... But none of that really matters all that much if it's blended in epoxy - except that now you might expect that particular Alumilite colorant to be more light-fast etc.

Some things to consider:

How will adding liquid (whether it is water, alcohol, or even oil and in what quantities) affect your cast? How important is opacity? Colorfastness? Do you need to be concerned about pigment settling? Which will help you get the most vibrant colors (or more importantly - the colors you're seeking for this cast!)? Does it have anything in it that is going to make my resin cure faster or slower?

Are you planning to use the colors as is, or is ease of blending and even potentially color-matching important to you? Mixing and matching with liquids is generally easier than powders. Some have actually found acrylic paints to provide a easy entry point for color matching, but these are typically water based so you have to be careful with cure inhibition especially in urethane resins (but even in epoxy, don't overdo it). There are plenty of people using Alumilite dyes or others for their color matching (Be sure to check out Fiscal's infamous color recipes) but I've yet to see anyone a powdered pigment to color match (unless it was black or white or something).

And most important of all, what do you have access to? The best pigment is the pigment you can use!

There's plenty more information that can be added to this page in time (glow in the dark, thermochromic, photochromic, metals, micas, etc, etc...), but for now hopefully that helps.