Pre-Boil 6.25g, 1hr boil, post-boil 4.0g?

[hezagenius]

Does that seem possible?

I guess this isn't specific to AG but I was doing an AG batch. I doubt that matters. The only thing I can think of is that the burner was too high. It is a 5psi regulator and it takes about 20-30 minutes to get 6g to a boil so I'm surprised I lost almost 2g in 1 hour.

 

[steakandale]

Yikes that a big drop! Probably overshot OG a bit too! (could be a good thing)
You could probably back it off a bit on the next batch. You just need a nice roiling boil, doesnt have to be a volcano.

 

[hezagenius]

I actually got a sub-par efficiency (65%) but I hit the target OG pretty much right on. I will just have 1 less gallon than I'm supposed to! Oh well, it was my 2nd all grain (same recipe as the first) and I improved my effiency 10% so it's getting better. I only lost 1 gallon on the first batch and used the same settings for the burner. Just means I will have to brew again sooner!

One other idea - it was a windy day so maybe the wind blew away more vapor than normal?

 

[whatisitgoodfor]

Unless it took a drastically longer amount of time to reach a boil compared to your last batch, I'd be much more likely to guess you misread pre-boil volume.

To boil off 2 gallons, I've got the surface jumping enough that I'll get splashes over the edge (2+ inches above the surface) so boiling off 2.25 gallons accidentally sounds suspect.

 

[mikeysab]

I boil off 2 gallons in an hour. If I get a boilover, I lose more. Did you get any boilovers?

 

[Ohio-Ed]

What is the diameter of your boil kettle? The exposed surface area has an impact on the boil off rate.

 

[lpdb185]

i do 5gal batches in a keggle. today, i started with 6.75g pre-boil and ended up with ~5g post-boil (4.75 after CFC). i just topped it off with filtered water to get 5g, then added the .25g starter.

my problem was that i had the burner cranked up a little higher than i thought. i only lost ~1.5g last time.

 

[mrfocus]

I have a quite large boil kettle (16" in diameter, 50qt in volume) and with a 1 hour boil I loose between 1.8-2 gallons (that's with a just rolling boil). Also I have a 45000 btu turkey fryer burner and when I get a boil I turn it down just enough to keep it boiling.

I have to use quite a bit of sparge water (6.6 gallons for 10 lbs of grain and a 6 gallon batch).

 

[hezagenius]

13.5" (143 sq in)

No boilovers

 

[mrfocus]

So you have a surface area of: 143^2", whereas I have 200^2". Boil-off depends on quite a few different things, but I would say you may be boiling with too much power (of course you want to keep a rolling boil as well).

 

[SamuraiSquirrel]

You did the exact same thing I did on my first batch!

I had the exact same problem as you on my first batch. I used about six gallons pre-boil and ended up with four gallons of wort .... and so became the "short stack IPA".

Since then I have just compensated accordingly and have my boil-off down to a science

Your boil off isn't that unusual. I have a 10 gallon megapot and use a turkey fryer burner. I have done 10-12 batches batches on it. I have always boiled of just over a gallon per 30 minutes boiling time. This is rain, shine, sleet, snow, 20 degrees, 70 degrees doesn't matter. Pretty much always consistent.

So if I am doing a 5.5 gallon batch with a 60 minute boil, I use 7.5 gallons pre-boil.

If I am shooting for a 5.5 gallon batch with a 90 minute boil, I use 8.5 gallons.

This works extremely well and provides great consistency with hitting that final volume.