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Mash - Thickness/Temp


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I do a fairly standard whiskey mash. Right now, I am using about 51% blue corn, 16% Distillers malt, and 33 percent rye. I grind everything into a flour.

This past weekend, I had a stuck fermentation which never really started. This happens to me fairly randomly. Most of the time, I have no issue whatsover and the ferment takes off in about 12 hours. I use a standard distillers yeast. But every once in a while they don't start. This leads me to a few questions which might explain what is happenning. It seems when I get stuck it may be because the mash it too thick or too hot.

What is the optimal temperature of water to mash at? Should I mash the rye and corn at a hotter temp and then put the barley in later?

Typically I put it all in at once with close to boiling water and have no problem.

What is the optimal ratio for water to grain?

I've been doing somewhere in the range of 6 gallons to 12LBs of grain. I think this weekend, the mash was more in the range of 14-15 lbs. It seemed too thick.

Also, what temperature do you do your ferments at? I've been getting good results starting at 90 and letting it stay at around 75 after that. I typically let the ferment go 7 days but it is typically done by day 5.


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Your grain ratio doesn't seem to be much of a problem, but your malt should go in at high 140's, low 150's F. Your enzymes aren't going to convert very well, if at all, when you start getting higher than 175 F or so. No matter what, you're well above optimal conversion temp. Try adding corn and rye as you normally do, then put in your malt at 150 F. The amount of malt you're using seems to be more than sufficient, I think it's more the enzymes not liking the temp. FYI, you can also get liquid enzymes that can help thin your mash at a higher temp when you put in your corn/rye and/or to help convert your starches. You can also throw in a handful of malt to "pre malt" or even "post malt" once the corn & rye are in. There's also liquid enzymes you can get to help break down the beta glucanase from your rye. On a separate note, get you some brewing books and study up on the different grains, their makeup, what's in them, how to best cook them. And then there's enzymes, learn them, love them.

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Thanks. Maybe it is the temperature. I haven't done too much with temperature control because I have been doing mostly corn and wheat mashes. I've never had an issue with them. Rye seems to be a different issue.

The one issue I have with resting temperature and holding temperatures is I do not have a set up with allows for holding temperatures well. I have a 26 gallon Hillybilly still set up that I use to get to about 180F. I pregrind the grains while I heat the water up, and then drop the water on the grain at 180-190F. It drops the the temperature to around 160 which typically seems to be right for conversion. I use a distillers malt and always get pretty good conversions. After about 5-6 days or fermentation I am at roughly 7-8% ABV. Now that I am using rye, that seems to be the problem.

I'm interested in holding the temperatures and resting with rye but my concern is burning the mash. My hillybilly still set up uses a heating element and a thick mash tends to burn it. I ferment on the grain and distill on the grain and if i heat it to fast I burn.

This is what I am going to try tomorrow. Heat water to 180 or so with heating element. Turn heating element off. Drop in the corn and rye. Agitate and wait until it drops to about 160. Add the ground distillers malt. Turn on heating element very low to maintain heat and agitate every few minutes (I use a power drill and paint mixer) for about an hour. Then drain into fermentation buckets and use a whirlpool chiller to drop tempt to 90F. Add distillers yeast at 90F. Set space heater for 85F. Ferment for 5-6 days at 85F.

Does that sound reasonable or am I still likley to burn with the element?


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Thanks for the help. I added the malt at about 150 and kept it between 150-140 for about an hour while agitating periodically. I don't have an iodine test (where do I buy one) but it looks like I got great conversion this time. The fermentation vessels are bubbling strong and overflowing out of the airlock hole (I use buckets with a hole for airlocks but no longer use airlocks).

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  • 6 months later...

Unfortunately the answer to that question is "it depends".

It depends on how effective your initial saccharification is (i.e. your starting SG).

It depends on your yeast strain - some are more alcohol-tolerant than others.

It depends on your yeast attenuation - the amount of sugar the yeast will convert before it just naturally "gives up" (which is somewhat, but not specifically, related to the point above).

At a high level, I'd suggest that if you're trying to manage your wash ABV by managing your input grain, you're probably over-graining (I made that term up). It's possible to get a wash ABV of 8-9% using as little as 1.25 lbs/gallon, depending on the grain.

I know, just from the little time that I've spent here, that the following is sort of a standard, cop-out response, but having done the research I can also tell you it's very sound advice - pay a visit to some of the home/amateur distilling forums. There's TONS of good information locked away in some of those good 'ol threads.

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