Pigments in soap dough (each got at least 3 days of drying time).
I = safflower lake (see above), C = commercial curcumin, L = turmeric extract lake pigment (see above), V = red oxide, A = commercial alizarin lake
K = turmeric powder straight into soap dough.
I'm pretty happy how the turmeric performed, for several reasons: First, it seems stable so far, and the colour intensity is convincing. The colour purity (saturation) is much better than for the whole turmeric powder = more orange, less brown! Should I ever tint soap with turmeric, I'll definitely not just sprinkle the spice powder into the batter, but leech it out with lye first and filter off the insoluble remainders.
Then, the hue. The pure curcumin is fine, but too close to the safflower yellow to be a fully independent colour. Not to speak at all about the turmeric powder.
I'll see if I'm still that happy when actually using & blending the colours. (A lake from purified commercial curcumin is on the agenda too!). The self-extracted curcumin (lake pigment) is much more reddish (“blood orange”). It looks like it might blend well with the alizarin to give reputable, saturated reds.
Another bad thing about the curcumin is that it migrates (bleeds) inside soap. I have some hope that the lake pigments don't (or at least only to a lesser degree). Comprehensive tests are in preparation.
The lake is quite similar to the red oxide in hue, though lighter and a bit more saturated.
One thing to improve with the curcumin lake is that it's still somewhat speckled/flaky. I did my best to grind it up, and ruined my mortar meanwhile:
(I hope that I can etch away the stuff with alcoholic KOH solution).
This is all still pilot scale/proof of concept. For the next iteration, I'll scale up a bit (10 g mordant or so), and use a very fine sieve to sift out the less ground-up pigment particles.
A big fan of turmeric already, I still can hardly believe that it is so easy to increase its cataclysmic colour strength even further, with (more or less) household means!
