FEEDBACK FRIDAY: This Week in Natural Dye Questions

This week: Cochineal for more than textiles and how long does it keep, and what to do about a murky alum bath

Every week, we are emailed with questions from our natural dye community asking simple and complex questions that we thought might be worth sharing. Of course, all of your burning questions are answered by natural dyer in chief, Kathy Hattori, Founder of Botanical Colors.

I’ve been wondering if cochineal would make a suitable colorant for shellac, to be used as a wood finish, and how it would compare to the highly toxic traditional cinnabar-urushiol lacquer. Obviously, cochineal is a transparent dye compared to the opaque mercuric sulfide pigment of cinnabar, so it wouldn’t look identical, but I think it would be beautiful in its own right. Shellac has been used for centuries as a music instrument varnish, my intended purpose.

We don’t recommend using cinnabar (HgS) due to its toxicity, and if you are using it for historical varnish purposes, I hope you are taking serious safety precautions. The original color of shellac is quite red because the resin secretion of raw shellac, called sticklac, is filled with lac insects, which are removed when the resin is crushed, washed and refined.  You could also experiment with lac dye. Both insect dyes are quite purple-red compared to cinnabar, which is a mineral pigment and has a reddish-orange shade. To achieve some level of opacity, you would need to turn either lac or cochineal into a pigment and combine with shellac. Madder pigment has also been used as an instrument varnish, and would be a translucent orange-red. A madder lake or pigment would have more opacity.

If I don’t use up my cochineal bugs right away, how long can I keep them in their shipped state?

The dried bugs are stable for several years if kept dry and away from excessive heat and light. I keep them tightly covered (in a glass jar) as well since they are full of protein and fat and some other critter might find that an interesting snack.

I am using your Tannin Extract (gall nuts). After scouring, I’m using hot tap water and tannin @ 5-10% WOF, stirring frequently for a minimum of one hour (usually I leave it overnight). I read on your blog NOT to rinse after the Tannin bath, and proceed straight to mordanting.

Here’s my issue, I have a very big alum mordant bath going, which I refresh when needed. Sometimes I mordant 10 shirts at a time. When I’m putting the tannin soaked goods into the alum bath it’s contaminating my alum bath, so my alum bath looks like a light muddy water with sediment at the bottom. In this case, should I not be re-using my alum bath but starting with fresh water each time? Should I be rinsing or drying the goods after the tannin bath but before mordanting? I hate to waste water and I’m trying to re-use it as much as possible. I am also doing a wheat bran bath after tannin/alum mordant.

The reason that we don’t rinse the tannin is that it isn’t really attached to the textile with a cold water soak, so rinsing can wash it off. I think ancient recipes instruct dyers to boil the heck out of their tannin baths to set it better before moving to the next mordant step, but we are trying to avoid the boiling. I am using and re-using my murky alum bath without a problem, and just went through a large production this way.

The only time I do a quick rinse is if I have a lot of tannin sediment on the textile. I’ll basically splash the area that has the sediment to dislodge it.

I don’t rinse after tannin, and I also don’t rinse after alum. Again, water and energy savings.

Check out Catherine Ellis’ book on natural dyes. She covers cellulose mordanting in detail, and I’ve used her methods with good results. Other dyers have variations on these methods and they also work well.