Non uniform mash temperatures

I'm returning to homebrewing after a break of about 15 years. I still have an early rims setup using a rectangular picnic cooler with a custom stainless liner/stainless screen "false bottom". I quit because of the length of brew/cleanup sessions, but was making some very good pilsners....

Anyhow, although I see much discussion of equipment setup in the other forums, not much of actual brew session practice. More in this forum.

Anyhow, I recall trouble with 2 particular issues: low extract rate - I'd get a final wort of about 1.035 rather than 1.048, and have to correct it with DME.

I also found that temperatures at various levels in the mash tun varied quite a bit: several degrees higher at the top than at the bottom. Well, heat rises, and the heated recirculation is added at the top. The whole idea of recirculation was that mash temperatures would stabilize but they didn't seem to, and I recall turning off the rims and stirring the mash by hand.

I stopped brewing before I resolved the issue. And maybe it's a non-issue, I don't know...

Any thoughts on problems with/managing temperature variations throughout the mash, particularly with rims and herms systems?

Thanks for your thoughts...

Well, you're right- in theory, the RIMS should equalize the temperatures. I don't have any great advice (I have a HERMS, but usually don't even use it) but as far as efficiency, there are several main reasons for low efficiency. One is simple- the crush. If the crush is bad, your efficiency will be low. There can be other causes- mash pH, etc, but the first place to start is looking at your crush.

Welcome to the forum- we'll be glad to help you solve some of these issues and feel free to ask any questions you may have!

I also wonder if other people are even measuring mash temperature at several different points in the mash tun. Maybe for the small mash volumes we're dealing with, an average with a few degrees variation top to bottom is all that matters: sure, there will be a range of enzyme activitiy but maybe it averages out... Dunno.

Re the grind - I have an adjustable 2 roller maltmill, which doesn't mean I was getting a correct grind. I recall worrying about a stuck mash more than extract in doing the grind.

gmartin said:

I also wonder if other people are even measuring mash temperature at several different points in the mash tun. Maybe for the small mash volumes we're dealing with, an average with a few degrees variation top to bottom is all that matters: sure, there will be a range of enzyme activitiy but maybe it averages out... Dunno.

Re the grind - I have an adjustable 2 roller maltmill, which doesn't mean I was getting a correct grind. I recall worrying about a stuck mash more than extract in doing the grind.

Click to expand...

Oh, I think it's important to have uniform temperatures throughout! I take the temperature throughout when I mash in- if it's different in anyplace, I stir until it's the same. In a 10 gallon batch, you should be able to stir well enough to get a uniform temperature throughout. If it's different in one place, stir some more!

I crush at .035", which is a bit conservative. I never have had a stuck mash or sparge.

gmartin said:

Any thoughts on problems with/managing temperature variations throughout the mash, particularly with rims and herms systems?

Click to expand...

I just do a straightforward infusion mash, and I regularly see a 5F or so temperature spread in the mash. It's still within range of enzyme activity so I don't worry too much about it. I get efficiencies in the 80's usually.

I've noticed that the thinner the mash, the more consistent the temperatures are - so I've been tending towards thinner mashes lately. This works for me for everything except higher gravity 10gal batches.