Hi All. So I have a question about calculating pre-boil volume for an all-grain recipe. I find a lot of recipes that call for specific pre-boil volumes, but isn't that a number that would be very specific to someone's system? Obviously you want to add in water to account for evaporation rate. But I'm curious, do most of you add in water to account for kettle trub/deadspace and shrinkage due to cooling? Or, do you worry about pulling too much wort and thus pulling unnecessary tannins?
There are several types of volume losses to account for that affect how much total water you need. Not all apply to all systems. And the volumes/rates do vary from system to system... Hot Liquor Tank dead space Mash Tun dead space Grain Absorption Boil Off Hop Absorption Kettle Deadspace Transfer Losses Software helps.
@VikeMan, thanks for the response. I totally agree that software helps. I use BeerSmith, however I sometimes find that it's become more of a crutch than anything. It's harder to really understand process/issues/solutions when you don't know where the numbers are being derived from. Since all those factors can vary greatly from system to system, any idea why recipes even specify a pre-boil volume?
IMO they shouldn't. As to why some do...this is going to sound harsh, but I think it's because some recipe writers don't understand WTF they are doing. It's kind of like specifying mineral additions or acid malt additions without knowing the starting water profile.
Recipe volumes are first-approximations. With or w/out software ... it's still a matter of trial'n error until you dial into _your_ system.
I'd suggest that the recipes authors are showing a little about their process, gravities, and what you should end up with. Just an OG and a FG may not account for a 3 hour boil that you're doing on that untraditional Strong Scotch Ale. It's good to get a few ballpark numbers so that when you're way off in the preboil, you can make adjustments with DME and rescale your hops.
It will depend of your system and the efficiency. I recently brew my 1st all grain and i use a recipe i found but ended up with almos 700ml more than what i was aiming for, of course my OG went down as hell but still good for the style i was brewing. From this experience i think the best advice is, write down everything you do, i think my next batch will be closer to the recipe in terms of volume and OG.
