Thanks to Doris Baltzo and the other attendees of a recent Tilden Lichen Workshop for bringing up this topic.
I guess the short answer is, “Yes, of course lichen dyes can be used on cotton!” However, the fiber type and the specific methods used may produce varying results. Despite my personal lack of experience on this topic, here is what I have learned in my review of some of my go-to dyeing resources:
In her book “Lichen Dyes: The New Source Book”, Karen Casselman has an inspiring list of things that can be dyed with lichens, including natural (animal/protein- or plant/cellulose-based) and synthetic fibers: alpaca, angora, cashmere, cotton, dog hair, linen, mohair, Orlon, quivet, rayon, silk, wool, paper fibers, synthetics, ribbon, lace, cane, reed, basketry fibers, feathers, leather, hair, hide, marble, wood, veneer, grasses, dried flowers, eggs, bones, buttons (even plastic ones!), food.
However, anyone who has done much natural dyeing knows that each type of material takes dye in a different way. In particular, the result of dyeing protein fibers can be brighter/deeper/darker than it would be on most cellulose fibers…though this may only be the result of attempting to use the same process for two very different types of fibers when each needs its own method.
Various washing/scouring methods have been suggested for cleaning cotton prior to dyeing, since it can contain wax, oil, or other substances that might impede dye uptake. Also, other aspects of the dyeing process, such as lowering dye bath temperatures and using different mordants, might work best for plant-based fibers. I have heard much of aluminum acetate (alum acetate) being used as a mordant on plant-based fibers (though it is NOT used for animal-based fibers), whereas aluminum sulfate, aluminum potassium sulfate (potash alum), and aluminum ammonium sulfate can be used on all fibers. However, in her book “Harvesting Color“, Rebecca Burgess suggests a pre-mordant of alum followed by tannin for plant-based fibers such as cotton, linen, or hemp. In her book “Wild Color“, Jenny Dean also suggests the use of tannin and alum, successively, when preparing vegetable fibers for dyeing. (See Jenny’s post for more info: Dyeing Cotton and Cellulose Fibres.)
Since lichens are substantive dyes (like a dye and mordant all rolled into one!), they themselves act as a mordant, usually requiring no additional mordant for the color to “stick”. Sadly, I don’t think we have enough available information to know whether lichens are sufficient to dye plant fibers without the use of other mordants…or more precisely, how lichens might work together with other mordants to produce different or accentuated colors, especially with the harder-to-dye plant-based fibers.
I would love to know the difference between using lichens alone, versus pre-mordanting with other commonly-used mordants, not to mention the different results of lichen dyes on various plant- and animal-based fibers. This is an area of study and experimentation that definitely needs delving into! If you know of any results, please post to the comments, below. If I get to doing some experiments, I’ll post my results, so check here for future posts on this topic…