My recipe i have used for about 10 years
STOCK :
1 BOX baking soda
1 box washing soda or (1 box baking soda baked at broil 20 mins)
vinegar to adjust pH of buffer
Stock Concentrated dry
6 part baking soda
1 part washing soda
mix very very.
to test:
1 tsp will raise the ALKALINITY Ka by 1 unit (on the D) in 25 gallons of water.
and should maintain the PH at 8.2
test a small sample
1ml into a fresh water gallon.
test pH and check that its 8.2 (the buffering capacity of the two)
test Ka: before and after
it should be pretty high. due to this sample being very concentrated.
check a 5 gallon bucket by adding 1ml of the dry powder
it should read 8.2 ph and the ka should raise by 1 unit.
keep as dry stock and make a pop bottle up with a tsp. or so.
do not increase Ka by more than 1 unit a day