Re: raspberry leaf tannins (uhm, opals)
I am trying to think of a good example and the only thing I can think of is an experiment I am working on making opals. I am not going to give away all of my secrets, but basically I mix a few things together and subject them to heat. Then I add water to make a solution. Then I add a second solution which forms a gel in the new solution. This gel then precipitates (settles out of the solution. This will eventually harden in to an opal.
Fascinating. This mentions "precipitation" and silica. I think we *may be* straying quite far from tannins in raspberry leaf though. :-)
http://www.colored-stone.com/stories/jul01/synthetic-opal.cfm
I saw a necklace recently, made of some sort of fabricated opal--forget what the clerk called it. But she emphasized it was a heat process--and 'recycled'. Oh yes, that's it--opal dust and "other stuff". Plus heat.
*Very* attractive.
Beguiling. I thought they were moonstones, but they were subtly different, like a cross bewteen a jelly opal and a moonstone. (Long ago, I did inventory for my sister's gemstone business, so I have some knowledge of stones) Strung between copper wire chain links, and really, really nice.
(the copper wire resonated a subtle violet in the 'stones'.
So, how different is what you are making? :-)