Boilovers, how bad are they for your OG?

I have been wondering this because I have been making a batch of high gravity Russian Imperial Stout type beer, codenamed "120 Otter Victory", and I have numerous boilovers when I brew this. Its got so much sugar in it and I believe proteins as well, that when bringing it to a boil, it will inevitably boilover.

The first time I brewed I hit low on gravity, was shooting for 1.100 and hit only 1.075. This time I was again shooting for anything north of 1.100 and I still hit low at only 1.090. But I had at least 6 boilovers before the wort calmed down.

How much sugars are lost during a boilover? I would wager there is a significant amount lost. Anyone have a concrete answer for this?

Have you tried Fermcap?

Is this an AG recipe? I believe efficiency losses are common when brewing the super big beers like this, at least compared to efficiencies you get on your system with "normal" beers.

My experience with boilovers is that it didn't make much difference. I guess maybe the stuff boiling out is a homogenous solution (sugar+water) and so you don't lose anything in gravity, you just lose volume. If your boil over was primarily sugar then you would expect to have problems with hitting your gravity as you'd then change the ratio of sugar to water in your kettle. HOpe that makes sense.

You are referring to Boilover while boiling the wort, correct?

I don't know how bad it is for OG, but I did have a pretty bad boilover on a batch once, and that beer was pretty weak. I'm curious to read the responses you get.

I started keeping a spraybottle with cold water in it by the kettle when I'm boiling the wort, and now I have a keggle to boil in, so there's lots of room.

If you're doing a full boil, it won't change your OG at all. You'll just have a little less volume. If you're doing a partial boil, your OG will drop a little, but unless you're having massive prolonged boilovers, it's probably not enough to worry about. It'd be easy enough to calculate, if you had a reasonable estimate of the boilover volume lost. Would also depend on whether you accounted for the boilover vlume by using extra topoff water, or just went with a slightly smaller total volume.

FlyingHorse said:

If you're doing a full boil, it won't change your OG at all. You'll just have a little less volume. If you're doing a partial boil, your OG will drop a little, but unless you're having massive prolonged boilovers, it's probably not enough to worry about. It'd be easy enough to calculate, if you had a reasonable estimate of the boilover volume lost. Would also depend on whether you accounted for the boilover vlume by using extra topoff water, or just went with a slightly smaller total volume.

Click to expand...

Good point about full vs. partial...my answer assumed full boil.

You know what they say about assuming things....

Well, to clarify a little, the boilover is the foam that begins to form on the surface of the wort as it starts reaching boiling temperatures, you know, that creamy stuff that you have all dipped your finger in to see how it tastes. Thats what is mostly spilling out of the pot, running down the sides of the pot and then baking onto the side of the kettle.

As far as how much liquid it is, not all that much, what spills out of the kettle is mostly the foam and a small amount of liquid, I'd estimate it at around 1-2 pints of liquid.

My thinking is that all that foamy stuff is probably at least in some part extracted malt sugars? But its probably not enough to bring the gravity down by 10 points though now that I really think about it.

And a few specifics about the grainbill, its an AG recipe with a 5.5gal yield and it is 20lbs of grain. Yes 20. Mash is at 158* for 90 mins. 90 minute boil. 8 gallons boiled down to 5.5 of course.