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Adjusting for High OG

On some of my recent brews, I’ve had higher than normal OG’s. I know there are a variety of ways to adjust for this (assuming you don’t want to leave it as is), but I just came across a method that I hadn’t thought about before. Assuming you’re fairly consistent on your boil off amount, something I read talked about draining off a pre-determined amount of wort before you boil and replacing it with the same amount of water. I’ve heard of adding water to the collected wort to increase the volume and dilute it down before you boil, but not pulling wort and then replacing that same amount with water. The formula I saw was:

preboil volume-preboil volume*(recipe preboil gravity/actual preboil gravity)

I guess the advantage would be that you could keep the same volume in your kettle rather than adding to the volume that’s already in your kettle. Has anyone ever done this, and are there any downsides to the final beer that I’m not thinking of?

It sounds like a complex pain in the butt, with questionable premises and results. I wouldn’t advocate it. Just add a little water if you need to.

Usually your OG ends up high from one of two things:

A) you boiled too hard or didn’t use enough water up front, so then you might need to add water back in anyway, or

B) you don’t yet understand how to keep your efficiency consistent, which comes with experience, and may involve consistency of your crush (i.e., milling grains at different LHBSs) or different brewing methods (partial mash vs. all-grain, BIAB vs. batch vs. fly sparge).

I know based on experience that if I brew a typical 1.055-1.060 beer, all other factors staying similar, my efficiency will be right around 85%, whereas when I’m shooting for an OG of 1.090, I know my efficiency will drop to like 60% unless I sparge a lot more and plan for a longer boil, etc. And interpolate in between. But if I always brewed every beer at 1.060, I know I’ll always get very consistent OG because I have a consistent process.

In other words, you need to know what your efficiency will be for each batch before you brew it. Don’t just assume it will be 75% all the time because a recipe or software says so. It’s not true. Find out how YOUR efficiency behaves in YOUR process, then design the recipes to work with that efficiency. Then you won’t run into these unexpected high (or low) OG issues very much at all.

If you find that your efficiency is jumping around all over the place, consider that your intended OG, your process, your sparge volume and your boil time all have a big impact. With experience, you’ll figure it out. In the meantime… if you need to make post-boil adjustments one way or the other, just do it. I typically don’t need adjustments, but when I do feel it necessary, it’s usually only like 1 quart in size – not too far off and thus optional.

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