Pre-boil volumes and extract or large amounts of adjuncts
I'm referring to pre-boil volume to counter for boil off. This is a general issue so it's not extract only but I will use that as an example. I brewed a Weizenbock this weekend and used 8.5lbs of DME. Obviously that takes up a lot of it's own space in the kettle so for example, if you were to fill for a 6 gallon pre-boil (5 gallon batch) and you start with 6 gallons, once you add the extract you are now up to over 7 gallons in the kettle and now you might not boil down to the final 5 gallons.
Another example is when I made my pumpkin. When I did mine I factored in that the 60oz of pumpkin is not a liquid but a mush that will likely mostly all settle out. So, I compensated with 60oz of top off liquid (I filled the cans with water to match up the fluid ounces and it matched the weight ounces). The thing though is my gravity came out a tad lower than expected - exactly the same as if I originally calculated for a 5.45 gallon batch with no pumpkin. But technically there was only 5 gallons of water and 60oz of pumpkin so I'm a bit confused as to why this is.
So I'm guessing when doing extract I should only fill to pre-boil volumes after adding in all the extract? Additionally since my pumpkin went into the boil at 30 minutes should I just ignore the extra volume and stick with the usual pre-boil volume? Sorry if any of this is worded confusingly.
Depending on how long it takes to get cranking, and how many times you have to remove to add extract, you could be looking at a half-gallon, maybe more, maybe less.
Easiest tip: have some quick way of checking on your pot for the 5-gallon level (I ballparked the length of my paddle to the surface of 5-gallons in the kettle, and go roughly based on that) and add either cold water VERY slowly from time to time, or add the odd splash of boiling water (we have a hot-water kettle that keeps a temp of 208 for up to a gallon that would work well.)
Also, subtract the volumes of extract going in, and don't count whatever might be removed later anyhow (pumpkin.)
I'm guessing the main thing is to have all ingredients in before setting the pre-boil volume. Or, what I've been doing lately with my smaller kettle and partial boils is add the extra volume as I go. With my 5 gallon kettle I've been adding boiling water to the kettle to compensate for boil off and keep as much as I safely can boiling in the pot. With my Blichmann on a floor burner I imagine I can even add cold water here and there if the level drops as that propane burner would easily keep a boil going.
Hefeweizen - in bottles
Belgian Wit - in fermenter
Pumpkin Ale - in fermenter, bottling this weekend
Weizenbock - in fermenter
Pumpkin Ale second brewing - hopefully this weekend.
So I'll have a nice pipeline in rotation :tank:
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