Daily Archives: July 23, 2014

trying to dye lichen for model foliage purposes

Name: John
Country or region: NZ
Message: Hi Paula
I am trying to dye a type of lichen for model foliage purposes. Because the lichen itself is known to produce a browny dye, when I try using a hot water dye the lichen turns brown instead of the desired green. Do you know if there is a suitable cold water dye that would work?

Hi John,

I think you probably don’t want to use dye at all, but instead a very thin transparent paint. There are only a few types of dyes that will work in cool water, and there’s not a lot of information on which of them work well on the material of which lichen is composed.

This is an interesting question, because lichens are not composed of the same material as plants or animals. Lichen is not made primarily of cellulose, like plants, nor of protein, like animals; instead it is made of chitin, the same long-chain substance used as a structural material by mushrooms, insects, and crabs. Chitin is a carbohydrate, a polysaccharide, made, like starch and cellulose, from many subunits of glucose sugar derivatives, hooked together in a long chain. The subunits in chitin are held together by the same sort of molecular linkage as cellulose, but each glucose has an additional amine group attached to it, which means that some protein dyes work on it. Unfortunately, protein dyes require heat, so they’re not useful for your question.

Cold water dyes work by chemically reacting with the substrate. Procion MX dyes, for example, which unlike other fiber reactive dyes work well at a room temperature as low as 21°C (70°F), react with cellulose or proteins at a high pH; a chemical such as soda ash is used to produce the high pH that is needed. The high pH might alter the color of your lichen just as the heat did. Of the three fiber reactive dyes I know of that have been tested on purified chitin, two worked at various pH levels, but one of them, the only Procion MX dye that was tested, did not perform well. I expect that some other colors of Procion dye might work better, but finding out which would be more trouble than I think it would be worth for you.

Chitin, unlike cellulose and protein fibers, has a positive molecular charge, so you can’t use basic (cationic) dyes with it. That’s just as well, as I do not like to recommend basic dyes, for reasons of toxicity.

I expect that you will want to use a particularly thin paint, so that it will be more like dye, and not change the texture of the lichen. A good thin fabric paint would probably be your best choice, as it is designed not to much change the texture of the fabric on which it is applied. In choosing a fabric paint, consider whether you want the paint to be opaque or transparent. Transparent paint will be thinner and give a more natural look, but, like dye, it will not be able to cover a dark color with a lighter one. If you need to lighten the color of the lichen you are painting, you must choose an opaque fabric paint, such as DecoArt SoSoft Fabric Paints, the opaque colors of Pebeo Setacolor Fabric Paint, or Jacquard Products’ Neopaque. If you do not need to lighten the color of your lichen, then you should choose a transparent paint that is very thin. Jacquard Products’ Dye-Na-Flow would be an obvious good choice–as the name implies, it is designed to be thin, to give an experience similar to using dye–as would the transparent colors of Pebeo Setacolor.

Both Setacolor Transparent paints and Dye-Na-Flow are available in several different greens, or you can alter the provided colors by mixing with other colors such as blue or yellow. For an even more transparent, lighter color, you can dilute Dye-Na-Flow with up to 25% added water, or you can dilute the Setacolor with Setacolor Lightening Medium. For a more realistic effect, you could start by painting with a light green, then paint unevenly over part of the surface with a darker shade of green; the results will be different if you apply the second color while the first is still wet than when the first color has already dried. Experiment to see what works best. All of the paint colors can be mixed with any other color in the same brand name of fabric paints.

When used on fabric that will be washed, both Dye-Na-Flow and Setacolor fabric paint are made permanent after drying by heat-setting them, but for model foliage that will not be touched, simply letting the paint dry will be sufficient. You won’t need to bother with the heat-setting step.

You can order Dye-Na-Flow or Neopaque fabric paints in New Zealand from ZigZag, which is located in Christchurch. If they have availability problems, you can order Setacolor Transparent fabric paint from Kraftkolour, or Dye-Na-Flow and other Jacquard Products paints from The Thread Studio, both of which sources are in Australia.

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