Store-bought tamarind comes in many forms. There's whole fruit that you can pick up from the Hispanic markets, or the pre-packaged fruit pulp. And then there are the containers of tamarind juice that come in all sorts of concentrations. I've tried a couple of recipes with tamarind, and they were annoyingly vague about how much tamarind to utilize.
Imagine my disappointment the first time I tried tamarind with a scratch Vindaloo curry recipe. The tamarind juice I bought was so concentrated that it wasn't quite compatible with the original recipe. My first indication of failure was that the curry was dark as night and thick as sludge. The first taste was beyond sour, and borderline inedible.
After that, tamarind was dead to me. Fast-forward about 3 years, I've been on a Thai stir-fry kick lately, and I saw this guy on the market shelf.
Tamarind Juice Concentrate
Add some sugar, fish sauce, and a dash of soy, and you've got the main ingredients for the sauce in pad thai. After a few iterations, I've managed to get the procedure down to where the noodles weren't practically disintegrating on me, and the finished product wasn't a dried out mess at the end. And fortunately, I diluted the tamarind enough that you can pick up its signature tangy flavor but not be horribly overwhelmed by it, like I've had in the past.