Some mash/brewhouse efficiency questions

[Ceejay]

I'm trying to gauge where I'm at in terms of efficiency, mainly to understand the concept and science a bit more, which should help me in future brews.

My last (first) brew turned out like this:

Volume of wort pre-boil 26 litres @ 1052 = 1352 degrees
Volume of wort post boil 19 litres @ 1060 = 1140 degrees

Recipe was this:

4200g maris otter pale malt
308 g crystal
308g choc
308g oats
190g roasted barley

Which i make to be a theoretical extraction of roughly 1540 degrees , using the figures in GW's book.

This means a mash efficiency of 87.8% and a brewhouse efficiency of 73.8%

I know I lost a couple/few litres when I was trying to figure out a new boiler, so I'm not unhappy with that result. Thing is, do these figures look right? I fly sparged and took my time over it - probably a good 50-60 minutes to sparge to 26 litres. Also, is it normal to expect that large an increase in OG from pre to post boil?

 

[Aleman]

Well given the fact that you took 7L out of the boiler while the sugar content stayed the same . . . then yes the OG will increase during the boil. After all 7 Litres is nearly 25%!

Otherwise your efficiency figures look pretty much spot on. You can afford to sparge a bit faster (down to say 45 minutes) without losing too much. slightly better wort recovery from the boiler will improve your overall efficiency.

 

[Ceejay]

Well given the fact that you took 7L out of the boiler while the sugar content stayed the same . . . then yes the OG will increase during the boil. After all 7 Litres is nearly 25%!

Thanks AM, that's what I thought. In terms of OG pre-boil then it's worth remembering that it should a percentage higher that post boil OG, commensurate with boil off %.

I don't think anything I've read really makes that very clear, IMO. It's a very simple concept but I think most of the books etc only express efficiency in terms of "overall efficiency", including boil off, loss to hops, deadspace etc.