Total liquor volume or final volume

[mcdonald_ajr]

I've seen this question raised a few times, but can't find the answer.

I understand the need to treat all the water (mash and sparge) to get the alkalinity down, so I use the total liquor volume to calculate the amount of CRS needed.

But to calculate the amount of gypsum and calcium chloride to add, should I use the total liquor volume, or the volume of liquor post boil?

I lose quite a lot of volume during the boil. To keep the maths simple, say I start boiling 30 litres and end up with 20 litres after 90 minutes. Presumably, if my desired wort should have say, 100ppm chloride, then if my liquor has 66ppm, it will be up to 100ppm after boiling a third off it?

Any thoughts?

Thanks, Anthony

[mcdonald_ajr]

Well, I've worked out my own answer to this question. If you want a specific ppm of, say, sulphate in your beer, then you need to consider final volume, allowing for other losses along the way, like grain absorption etc. if your boil is longer, then that will concentrate your chemical additions.

Of course, this is all a bit theoretical, and it is the taste that counts, but being a bit of a scientist I like to calculate things to excess!

As I can't fit all my runnings into my boiler, and have to have a pan boiling as well, I get a lot of evaporation, so need to be a bit more conservative with my chemical additions. I was finding the beer a bit too Sulphate'ty so have cut back a bit on the Gypsum, and much prefer the final result.

Anthony

[BenB]

If you're aiming for a particular ppm in the finished beer then yes but (and I'm still an AG newbie so take this with a pinch of NaCl) if you're trying to match a certain water profile or obtain a certain mash pH then you'll want to be working on the pre-boil concentrations. My understanding (from listening to the BrewStrong podcasts on water treatment) is that the ppm of, say Sulphate isn't so important as the ration between Sulphate and Cloride. The ratio obviously won't change with boiling.

[orlando]

I always treat the entire volume of water used but crucially I treat mash & sparge water separately. It isn't always necessary but there are times when it is and that depends on what sort of water you have to start with. I adjust alkalinity using acid and then add salts to adjust for flavour profile. By treating all the volume in one you can for example push your salt additions too hard and end up with over mineralised beers. Remember the most crucial aspect of water treatment is to get the mash pH right and to keep sparge water under 6. Treating them separately gives you greater flexibility across the style range.