Mash temp drop in my cooler

I partial mash with 6-7 lbs grain in a 4-gal cooler, and my temperature typically drops about 4 degrees in one hour. If I want to mash at 152, would it be better to start at 152 and finish 4 degrees low or try to hit an average temp of 152 by starting two degrees higher and finishing two degrees lower?

Someone asked almost the exact same question a couple years ago and the responses focused on ways to preheat or better insulate the cooler. I've done all that. Maybe I need a new cooler (mine's ~20 years old), but for now I'd really appreciate some advice on a starting mash temp.

Thanks!
Jason

Most actual conversion occurs in the first 20 minutes or so for most grain so raising the temp would prove to be the wrong approach

You either need a better newer cooler or figure out how to better insulate the one you have like a blanket wrap

Hmm... Interesting question! It's always been my belief that the majority of your enzymatic activity happens in the first 30 minutes of your mash. I've heard that a couple of times now, actually.
Personally, I think if I was in your shoes, I'd shoot for the 152 at the beginning and let it drop. Or possibly go 153 and assume that the one degree will be lost in the time it takes for the starches to start gelatanizing.

I must say, I too am interested to hear other's opinions on this.

I do have to admit though, my first thought was to ask you if you're making sure that it's pre-heated well before you dough-in.

I mash in a 10gal igloo currently and I usually only see about a degree of drop after 60 min even with all the extra headspace that a 5gal grain bill in the larger cooler has. With a 10gal grain bill, I usually don't even pick up a drop.

I agree that overshooting the strike temp will probably not give you the fermentable profile you are looking for with your wort. An option may be to dough in slightly thicker than you normally do and add some boiling water and stir after about 30 minutes to help keep you in the temp range you want.

Thanks for all the advice. Realizing now that most of the conversion happens within the first 20-30 minutes I agree that I should try to strike at, or maybe 1 degree above, my target mash temp.

As I mentioned, I do preheat my cooler, but maybe I'm not doing it as well as I could. I'll focus on this and if things don't improve I'll consider OClairBrew's suggestion of adding more hot water part way through. Thanks again to everyone!

What is your preheating procedure? I used to pre-heat with 150f water while my strike water was heating and still dropped temps more than I wanted. Last brew day, I pre-heated with 170f water while my strike water heated and dropped only 2 degrees in 60 minutes. I have heard laying a piece of aluminum foil over the top of the mash helps hold the temps also, but have never personally tried that.

you can insulate the lid by drilling it and spraying that foam insulation inside (use the stuff for around doors and windows...its expands less so it doesn't warp the plastic).

some will cut a disc out of pink foam insulation to float on top the grain bed.

OClairBrew said:

What is your preheating procedure? I used to pre-heat with 150f water while my strike water was heating and still dropped temps more than I wanted. Last brew day, I pre-heated with 170f water while my strike water heated and dropped only 2 degrees in 60 minutes. I have heard laying a piece of aluminum foil over the top of the mash helps hold the temps also, but have never personally tried that.

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Why not just hear you strike water about 10 degrees higher and use that to preheat. That is what I do and it works like a charm. Saves gas and water in the long run that way.

Breck09 said:

Why not just hear you strike water about 10 degrees higher and use that to preheat. That is what I do and it works like a charm. Saves gas and water in the long run that way.

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I have thought about that and will probably try that next brew day. It will probably save me quite a bit of time becuase I do everything inside on my gas stove and it takes a long time for my water to heat up.

I usually preheat for about 10 minutes with ~2 gal water, either hot water from the tap or heated to ~150 on the stove while my strike water heats. Both give me about the same temp drop.

I read about overheating the strike water, adding to the cooler and waiting to add grain until the temp drops to the target strike temp. I may try this along with aluminum foil (hadn't thought about that). I had considered the spray-in foam but backed off after reading about how nasty of a mess it can make. The pink insulation (Owens Corning) is expensive compared to other brands ($13.35 vs $2.40 at Home Depot). I always see people mentioning the pink insulation but I can't imagine it would matter if I covered it with cling wrap or something.

Just wanted to post a follow-up. I decided to lay some aluminum foil across the top of my mash and I only lost ~2 degrees F over 60 minutes in a cooler that was not preheated. I can live with that! I just pulled off an over sized piece of normal foil and did a trifold, like how your credit card bill is folded in the envelope, and placed it right on top of my mash. Couldn't have been easier.

Thanks to all for your suggestions!

I've noticed this exact issue with my 10g Home depot igloo. Even after preheating with 190º water and mashing a degree or two higher than I wanted it would ~still~ drop 6-10º drop over an hour. It was madding. I used the tinfoil as a grain bed protector in my last batch and noticed only a 4º drop. I may try wrapping some of my leftover insulation in plastic wrap and place it over the top of the tinfoil on my next batch and see how that goes. Thanks for the ideas folks.