SWIM has a question... it does not pertain to the STB method though.  Have any of you noticed a decrease in yeild when using sodium carbonate instead of sodium hydroxide in an A/B?  SWIM has read of people switching to this for safety reasons as well as ways of keeping under the radar (sodium hydroxide = meth).  also the ability to bake sodium bicarb into sodium carb easily at home.  SWIM thanks you!