Can you eco-print without using alum? Short answer: yes, if you like faint blotches of color. I've provided a brief description of what I tried, possible problems, and what I plan to try in future experiments.
If you've ever wondered if you can do an eco-printed textile using just the natural tannins in the plants, this experiment suggests that one answer is yes, if you want just a few blotches of color. Although I have two kinds of alum in my botanical dye supply kit (aluminum potassium sulfate and aluminum acetate), I was curious about what kind of results I might get just using plants, including ones that are high in tannins. Plants high in tannins, used for botanical dyeing, and commonly available in Hawaii include yellow onion skins, pomegranate rinds (fresh or dried - you get darker results with dried), kukui leaves (Aleurites moluccanus), rosemary, thyme, and eucalyptus leaves. Most natural/botanical dye books focus on plants available in North America and Europe; for tropical locations, I highly recommend Hawaii Dye Plants and Dye Recipes by Val Krohn-Ching.
I tried three textiles: a cotton/linen gauze (a scarf purchased at a markdown sale that I had previously tried dyeing with dried pomegranate rinds), a silk/hemp blend (fabric purchased almost 20 years ago that had been dyed at least twice but had faded when used as a curtain), and cotton muslin. The cotton muslin had the best results.
For these bundles, fabric was soaked in water and plant materials were placed on the damp fabric, rolled around a piece PVC pipe (the cotton muslin was tied around a bundle of rosemary branches without leaves), and tied with cotton thread. The bundles were then boiled. For the cotton/linen, the bundle was baked in a pan of water; the other bundles were boiled in a pot on the stove.
In addition to the lack of additional mordants, likely reasons why the fabric did take on some color overall but very little distinct printing:
- Boiling temperature was too high. This should be kept to a low simmer.
- Bundles were not tied tightly enough. The fabric ballooned out a bit around the wrapping and the ties loosened when wet.
- Not enough plant material. Additional plant material can be added to the dyepot.
For future experiments:
- Post-dye iron dip (update: tried it with a section of the cotton muslin, will post results later)
- Scour cotton fabric with soda ash before mordanting and/or eco-printing.
- Mordant cellulose fibers (plant fibers, like cotton, hemp, and linen) with tannin first, then mordant with alum, and then try eco-printing.
- treat cellulose fibers with soymilk before printing.