Another chemistry question or two

[mrsflibble]

ok, this is about vegetable pigments and how they react to acids and alkalis...


i gave onion dye a go last night using vinegar as a mordant (acid). it was a pretty peach colour... until i washed it. in soap (alkali). it's now a beautiful yellow and I love it.

Now, I know about the reactions between anthocyanins (purple veg shades) and acids/alkalis, and how red cabbage water goes a gorgeous pink colour when exposed to acid, and a fabby green when exposed to alkali... but i was wondering, does anyone know of a different mordant i can use to get the more purple shades of cabbage water? or to keep the fab pink that vinegar causes when used as a mordant and yet still be able to wash the thing? or the more peachy shades of onion?

and although I'd prefer not to use wee as a mordant, I will if it's a means to an end and if it allows me to keep the more interesting shadesd of veg dyes lol!!!

[wolfsong]

um, nothing you can get outside the lab, sorry
if you've got household ammonia chez vous, but i don't know the standard pH of that... The real stuff has to be cold.

[Cloud]

What about tannic acid. i think it is (was) use in leather and wool staining. No idea how you get hold of it though. I gather that the tannin in tea is no good. Does tannic acid come form oak?

[becks77]

Just found this site it may help
http://www.wildcolours.co.uk

[mrsflibble]

becks77, wonderful site thanks!

[Derry]

a fact: indigo flowers are yellow

[StripyPixieSocks]

I think indigo dye only goes blue when it reacts to air... or am I thinking of something else!

[Ellendra]

What about tannic acid. i think it is (was) use in leather and wool staining. No idea how you get hold of it though. I gather that the tannin in tea is no good. Does tannic acid come form oak?

Tannins are found in many plants, including oaks, willows, and sumacs. The easiest way to extract them is to chop or grind acorns, and put them in boiling water. Boil until the water turns very very dark (almost inky), then strain the acorns out and, if needed, simmer the water to concentrate it more.

This is also the first step in rendering acorns safe to eat, as the tannins need to be leached out first.

For harvesting tannins, look for the bitterest acorns. For eating, look for the mildest. (small amounts won't hurt you, so it is safe to taste them, although don't if you're anemic)

[mrsflibble]

wow, thanks ellendra! where i live is a 1/2 acre green packed with oak trees!!