I'm making some mustards for gifts... where in SF can I purchase 1/2 lb tamarind block?
You can get it at Haig's on Clement.
642 Clement St, San Francisco, CA 94118
I have struggled to get any decent yield out of the blocks in my Thai dishes. Whenever I see the liquid concentrate, I grab some. The concentrate I am referring to is authentic Thai product; simple plastic jar and red plastic top. Maybe it will save you some hard labor.
I use the tamarind paste that comes in the jar or plastic tub. Great consistency, easy to use and incorporate into other things. Would recommend that for your project.
Other good tamarind threads on CH.