Splitting the Difference

dan_s · June 30, 2013, 2:55am

Hello Everyone,

I have a question about mash temperatures and FG’s. After looking through my notes, I’ve noticed that I can reliably expect to lose approx. 4* over the course of my mash (I use a 70 Qt. Coleman Xtreme Cooler for my MT). It seems that no matter what the ambient temperature is or how many heavy blankets I throw over the cooler or how much insulation I use to fill any vacant headspace, I always wind up 4* lower than when I started.

This being the case, I’ve taken to splitting the difference with my mash temperatures, which is to say that I start 2* above the target mash temp. knowing that I will end up 2* below at the end of the hour.

Another problem that I’ve noticed is that my FG’s are tending to come out lower than expected, usually by 4-6 points, and I’m wondering if there is a correlation between the two.

Has anyone out there lived with this same issue of losing a predictable amount of heat during the mash? Should I perhaps mash 4* higher initially and aim to end at the target mash temp rather than splitting the difference? Also, would a thicker or thinner mash help with heat retention? I generally mash at 1.5 qt/lb.

Any direction appreciated!

taffin · June 30, 2013, 5:31am

Going thinner should help, but I’m not sure by how much. If it doesn’t help much, is adding a little hot water halfway through the mash an option? As an example, if you wanted a mash temp of 154, but halfway through you were down to 152, adding just .6 qts of boiling water would get you back to 154 (assuming you start with 1.5 qts/lb grain and 10 lbs of grain).

billy · June 30, 2013, 12:49pm

Do you pre-heat the cooler? I always pre-heat my cooler first, with 2 gallons of boiling water, and make sure you fill the empty space above the grain bed, a 70 qt cooler is a big one. When I do this I never loose more than 1 degree F.

r1 · June 30, 2013, 2:26pm

I preheat my 70 qt. marine cooler like Billy and get minimal temp loss. If it is cool out I will use a jacket around the tun made out of the foil, bubble wrap material.

dan_s · June 30, 2013, 2:38pm

Thanks for your replies.

I do preheat the MT, but I’ll typically only use hot water from the tap - about a gallon or so. My brew days are usually pretty hectic with a number of small children running around while I brew, and taking the time to actually boil water for pre-heating is something I just haven’t put into the schedule. Now that you’ve mentioned it, I’m guessing that the tap water is just not hot enough to provide for stable temps.

Taffin, adding water also sounds like a good option!

kcbeersnob · June 30, 2013, 3:25pm

It would drive me crazy to lose 4° over the course of an hour, but then again I’m a control freak. I’ve elected to prevent this problem by having two MLT coolers on hand. I use the one that’s most appropriate for the job. Temp is normally steady through the mash, although sometimes I lose a degree.

I’m curious. Although your FG is lower than predicted, how do the beers taste? Are you unhappy with them? Too dry for your taste? Too much alcohol? Too thin?

Do you see the same 4-6 point lower FG with every yeast strain?

kcbeersnob · June 30, 2013, 3:32pm

[quote=“Dan S”]
Now that you’ve mentioned it, I’m guessing that the tap water is just not hot enough to provide for stable temps.

Taffin, adding water also sounds like a good option![/quote]
You might want to try using your entire strike water volume to pre-heat the cooler. Heat it 5-10 degrees higher than your dough-in temp, add it all to the cooler and let it rest until it falls to your target dough-in temp, then stir in your grist. This should help a little.

dan_s · June 30, 2013, 5:13pm

[quote=“kcbeersnob”]Although your FG is lower than predicted, how do the beers taste? Are you unhappy with them? Too dry for your taste? Too much alcohol? Too thin?

Do you see the same 4-6 point lower FG with every yeast strain?[/quote]
I’ve seen the effect over a variety of yeast strains, with my biggest gripes being that I perceive the beer being thinner than I’d like with a higher ABV than anticipated. I’ve been happy with the way the beers have tasted, especially since learning my way around Bru’n Water. Above all, I’m also really wanting to improve the consistency and predictability of my process.

[quote=“kcbeersnob”][quote=“Dan S”]
Now that you’ve mentioned it, I’m guessing that the tap water is just not hot enough to provide for stable temps.

Taffin, adding water also sounds like a good option![/quote]
You might want to try using your entire strike water volume to pre-heat the cooler. Heat it 5-10 degrees higher than your dough-in temp, add it all to the cooler and let it rest until it falls to your target dough-in temp, then stir in your grist. This should help a little.[/quote]
I like this idea a lot! Especially since it would potentially eliminate the extra step of boiling pre-heating water separately. Thanks for mentioning it – I’ll give it a go later this week. I think I’ll also start checking temps. mid-way through the mash, just to be safe.

kcbeersnob · June 30, 2013, 5:49pm

[quote=“Dan S”]
I’ve seen the effect over a variety of yeast strains, with my biggest gripes being that I perceive the beer being thinner than I’d like with a higher ABV than anticipated. I’ve been happy with the way the beers have tasted, especially since learning my way around Bru’n Water. Above all, I’m also really wanting to improve the consistency and predictability of my process.[/quote]
Very understandable. I’m not sure a 4 degree drop over the course of an hour will fully explain the higher level of attenuation and other characteristics you’re seeing in the final product. After you get your temp under better control, you might find that you have to take other measures to fix some of those things. Also, FG predictions should be taken with a grain of salt. They are no more than an educated guess. Although I have steady mash temps, I still frequently see attenuation that exceeds the FG predicted by Beersmith.

[quote=“Dan S”]
I like this idea a lot! Especially since it would potentially eliminate the extra step of boiling pre-heating water separately. Thanks for mentioning it – I’ll give it a go later this week. I think I’ll also start checking temps. mid-way through the mash, just to be safe.[/quote]
I look forward to hearing how it works for you. You may have to experiment on a few batches before you get the right target temp for your equipment, so you don’t have to wait a long time for the drop. I’m guessing with such a large cooler, it should drop pretty fast.

nighthawk · June 30, 2013, 5:51pm

[quote=“kcbeersnob”][quote=“Dan S”]
Now that you’ve mentioned it, I’m guessing that the tap water is just not hot enough to provide for stable temps.

Taffin, adding water also sounds like a good option![/quote]
You might want to try using your entire strike water volume to pre-heat the cooler. Heat it 5-10 degrees higher than your dough-in temp, add it all to the cooler and let it rest until it falls to your target dough-in temp, then stir in your grist. This should help a little.[/quote]

This is my process also. I heat the water to ~170. Add to the cooler. Allow to set for 5-10 minutes. Temp drops to 160. Add grain and the temp drops to just above 150. Stir until it drops to 150. Close lid and walk away.

This is with 48qt cooler and 12-15lbs of grain. With everything being in a “room temp” range, 65-70*.