I just got a bottle of 85% food grade phosphoric acid and I used a spreadsheet to dilute some of it down to a 10% concentration. When I plugged all of my numbers into Bru’n Water, it says that I need 46ml of 10% acid to bring my mash down to 5.2. I’m brewing a Blonde Ale, BIAB 4 gallon batch. 5# 2 row, 8 oz carapils, and 5 oz aromatic malt. yellow balanced profile, with 5.6 gallons of RO water. I’m also adding 1.5 grams of gypsum and 1.5 grams CaCl. When using 88% lactic acid, I only have to add 5ml.
46ml of 10% phosphoric acid seems high to me. Does it take that much more to move the pH? Or did I do something wrong in the spreadsheet?
I have never tried diluting acid. But logically (and maybe too simplistic) it seems you added the equivalent of 46/8.5 ml of undiluted 85% acid. This is about 5.4 ml, which sounds about right to me.
Hopefully someone more knowledgeable will correct me if I’m wrong.
You didn’t do anything wrong in the spreadsheet. You just didn’t need to dilute. You could have just used the 85% in the spreadsheet and probably wound up getting about the same amount called for as 88% lactic.
10% phosphoric additions always freak me out but once you remind yourself that its 10%, in other words 50ml would only be 5ml at 100%… it calms me down