<<Disclaimer: Verify this information before applying it to your situation.>>
 
1/4 teaspoon baking soda to approx. 1 teaspoon or 1/2 tablespoon (1 1/2
teaspoon) rice vinegar, without additional liquid, works for me.
 
Cream of tartar is the residue in wine kegs, so I don't use it because of
grape/wine sensitivities.
 
More on baking substitutes: Since I can't use milk or commercial substitutes,
I use 1/4 cup tahini (sesame paste) with 3/4 cup water to substitute
for 1 cup milk; the rice vinegar helps dissolve the tahini (and dissolves
rice syrup or honey), too. I have also used 1 tablespoon rice vinegar = 1
egg, even in the automatic bread machine.
 
Ann von Mehren
Silver Spring, MD