Figuring out mash efficency for different volumes

[MikeRoy]

I have a 15 bbl DME system that I will knock out about 15.5bbls and yield around 14bbls. of finished beer. When I do a half batch for higher gravity beers I get a 50% ME instead of the usual 75-80ish%. Is there a formula for figuring out mash eff. for various volumes? I would like to be able to brew a volume inbetween these two but I'm not sure how to adjust and figure a ME without just making a run at it first.I understand there are a lot of variables for ME but wonder if there is a way to get a ballpark figure?

Does anyone understand what I'm talking about?

[pennbrew2]

Is there a formula for figuring out mash eff. for various volumes?

Short answer: no.

Longer answer: You can probably make a reasonable guess at it. Consider that the 2 main reasons you get lower yield in your half brew are 1) less sparge water and 2) higher relative loss in whirlpool/kettle bottom.

Since you're more familiar with your system I'd think you could come up with a fairly close extrapolation for your desired volume.

---Guy

[Fred Scheer]

HI Mike:

Guy is right in his post replying to your question.

I have some recommendation, based on what I did in the past:

Based on your #s, your evaporation is about 9.5%

I recommend to fill your kettle ~ 70%, which would be ~ 11BBl; K.O around 10 BBl. You know how much hops you are using in this brew; too much with low alpha will result in lot's of trub, which not only causes loss, also lots of trub will end up in your Fermenter. So, you alone know what the maximum hop usage will be.
Next, I would mash in in the ratio (liquid/grist) of 2:1; which would be the following formula:

2 X amount of malt/8.3/31 = strike water.

Have a longer rest in the range of 149*F to 154*F; about 75 to 80 minutes.
Lauter at a rate of less than 1 BBL per 10 minutes; start sparge when top of grist is visible in mashtun and keep that level. So, it is a slow sparge and slow lautering, which will help improving your ME.

Next, keep an eye on your mash pH. If not in the right range, your enzymes will not do the job.
Adjust your water with CaCL or CaSO4, depending on your water and the style of beer you want to brew.

I hope this helps a little bit and good luck

Fred