The June/July colors for Project Spectrum of Red, Black, and Metallic weren't the easiest ones for me to participate in but it got me thinking about the metals that we have and use around here, both C in the woodshop, and myself in dyeing.
Metal salts are frequently used as mordants in the process of "naturally" dyeing of fibers. They are not only used to "fix" the colors to the fiber but also different ones are used to achieve different colors from the same plants. Alum (Potassium Aluminum Sulfate) is considered to be the safest of them, frequently cited as being safe for even children to use. This is the only powdered form of mordant that I am comfortable using, in conjunction with cream of tartar, and still I do not include the boys in the mordanting of yarn.
Some other metal salts used as mordants are Chrome (Postassium Dichromate or Potassium Bichromate), Copper or Blue Vitriol (Copper Sulfate), Iron or Copperas (Ferrous Sulfate), and Tin (Stannous Chloride) all of which are extremely toxic. A Handbook of Dyes from Natural Materials, by Anne Bliss has terrifying descriptions of these that scare the living wits out of me and has certainly convinced me that I'll never, ever choose to use any of them. How I wish all dye books had such frank descriptions. Personally, I'd have a hard time calling my dyes "natural" if I were using such hazardous and deadly substances. Even if I didn't have children, I would never choose to have these in my house, no matter how well labelled and stored. The potential for danger would be too great and disposal of leftovers into a septic system or watershed could be devastating.
There are some safer alternatives to powdered metal salts, however. Lichens and some plants can either be used without mordants and can, themselves be used as a premordant for dyeing with other plants.
A somewhat safer alternative to using the concentrated Copper or Blue Vitriol powder is a Copper Penny Green that I learned of years ago in a lichen dye class. It can be used as a premordant, for overdyeing, or just as a dye itself. (The sagey greenish-blue yarn above was dyed in this way) Mix the following and keep in a nonreactive container such as a glass jar with a piece of plastic wrap between the metal lid and the contents:
Fifty pre-1982 U.S. pennies (pre-1982 they had a higher copper content)
3 and 1/2 cups water
1/2 cup ammonia
Keep in a nonreactive jar until color develops. No heat is necessary when dyeing. Just immerse fiber in the solution which can continue to be reused, topping off with more water and ammonia as necessary. Wild Color, by Jenny Dean has a similar version that uses vinegar rather than ammonia and lengths of copper pipe in place of the pennies. Another alternative is dyeing directly in an unlined copper pot. I have yet to try that one.
An alternative to the Iron or Ferrous sulfate powder is dyeing directly in an unseasoned iron pot, or creating a similar solution to the copper bath but with rusty bits of iron: nails, screws, lengths of chain, horseshoes, etc. These are methods that I often use. So many dye plants produce yellow tones but the same plants can often give a greenish or greyish hue in an iron pot. Wild Color also has a different version of this than I use that calls for vinegar and water as well.
Of course, these methods aren't entirely safe themselves I suppose but our kids are well aware that they need to stay clear of these things when they're out and in use. They would never be out when other children were here. And, of course, even with natural dyeing, you always use well marked containers and measuring cups and spoons that are designated only for use in dyeing.
None of this is new, I'm sure, to those who use natural dyes regularly. I just thought I'd share for others who might be interested or are newbies at it.
More catching up on the past month-or-so's focus on metallics in the next post or two or three. I know, I'm a little behind the times here but I figure I'm still on the cusp between the new and old PS color schemes, aren't I?
Regarding Tola's comment below: Good question. I haven't actually worked with this dyebath in awhile but I'd say leave the (wetted) fiber in for between an hour and 24 hours. When it comes out of the dyebath it will be a brighter blue but will change to a more sagey-blue-green hue.