Start your research here:

http://www.biabrewer.info/viewtopic.php ... rsion+calc

See, we really do have all the answers.

---Todd

This is a really grey area nu_brew. Basically there is not enough real data around on this. Most of the formulas we have are extrapolations of what happens at normal gravities.

Some weird stuff can happen at high gravities. For example, a few weeks ago we tried experimenting on this side of things. We had two identical grain bills of 15kg each.

Batch A was mashed in with 38 L of water
Batch B was mashed in with 32 L of water

You would think that the gravity of Batch B would be higher right? Here's what happened...

Batch A's digital thermometer broke and we discovered that we had struck at 75C. Batch B's thermometer was fine and we struck at 65C.

Batch A's gravity was 1.080
Batch B's gravity was 1.060



Btw, we were chasing a pre-lauter gravity of around 1.085 (Batch A) and 1.119 (Batch B) at that stage of the brew.

So, one thing that is important is the liquor to grain ratio can get to a point where efficiency rapidly decelerates.

The auto-efficiency feature in the BIABAcus we are working on estimates an efficiency into kettle of 63% for a 1.100 beer. Stux's calculator gives the same result (and it should as the formula we are using comes from stux's calculator . However, stux's calculator gives an even higher efficiency if you sparge and there is doubt as to whether sparging makes any real difference at least at normal gravity levels when compared to full-volume brewing. At high gravity brewing, the same result could well be true and could even reverse as the 'real' first runnings efficiency so rapidly decreases as the liquor to grain ratio decreases.

If I was in your position and had been achieving 80% on normal gravity brews (1.050)I would go with the 63% efficiency into kettle estimated above and full-volume mash it. I would also have some extract on hand if needed.

Finally, I'd do some googling and see if you can find some good info on high gravity brewing that are based on actual brews. Maybe there's some good articles out there?

Would love to hear how you go ,
PP