How do I make sure spice mixes don't make my curry grainy?
I make a homemade enchilada sauce that calls for 4TB of chili powder for 2C of chicken stock.  I make my own chili powder by grinding dried chilis in a coffee grinder that I use for spices.  I make sure that the powder is finely ground. To make sure the final product is not grainy, I cook the sauce for at least 25-30 minutes at a bare simmer, whisking every couple minutes.  The end result is a reduced sauce that is silky and creamy without the graininess.  Even though your powder may seem fine in texture, you might try running through your spice grinder and add some extra cooking and whisking time.