importance of mash temperature?

Ok, I've done several AG batches now. I tried BIAB with decent success but grew tired of holding heavy bags of grain and so I bought a bazooka screen that fit into my 10g kettle to use it for batch sparging. The first time I used this I quickly realized that maintaining the mash temp for an hour was a problem. My efficiency came out to 60% or something. Then I bought the Reflectix insulation stuff I've seen mentioned here on the forums to help with insulation. This helped hold the temperature for an hour but I still think I missed my target mash temp by a few degrees, and again the efficiency was crap (~60%) yet again. So the question is, would a 146-147 temp contribute to low efficiency? That's the only thing I can think of that's not going according to plan.

More details for those who might be able to help...

• I ran an iodine test and it looked to me like the conversion completed (no blue colors after mixing the iodine w/ the wort sample).
• I'm using Austin Homebrew grains that are pre-crushed
• BobbyM's no mash out double batch sparge was the technique I tried to follow
• I used BrewTarget to calculate water volumes (1.25 q/lb mash, sparge was two ~3g volumes)
• I've tested water PH in the past with PH strips and it seemed to be ~5
• The kettle spigot is a little bit raised from the bottom. I figured out that I lose about 1.2 gallons of wort at the end of the boil if I don't try and tilt the thing at all. I'm not really sure how much I'm losing during the mash since a lot of the liquid is absorbed into grains and makes it hard to measure what gets left behind in the kettle during that part.

I always thought the lower temps would just mean dry beer and higher fermentability. Any ideas what could be causing my problem? I'd really like to get up in to the high 70's or lower 80's for efficiency.

While there's nothing wrong with 1.25qt/lb, you might try upping it a little. A slightly thinner mash is supposedly good for better conversion, and I also do the double batch sparge to rinse all the sugar out I can.

Nothing wrong with tipping the mash tun, the screen should help filter stuff out.

you are vorlaufing, yes?

Any mash temp under 149* will mean that not all the starch has gone into solution. I think you'd get a better efficiency if you held it for some time above 150*. Two batch sparges will also help, as will thinning out your mash, like malkore said.

149 should be fine, so long as you do a 10-15 min mash out @ 165-170F

@malkore - thanks, so maybe 1.2 instead of 1.25? or even thinner? 1.1? and yes i was vorlaufing almost a gallon and pouring it back.

@indigi/electric beer - ok, well the *intended* mash temp was 152. the issue was that i'm still getting used to how much heat i lose at the beginning as temperatures are stabilizing and so i'm missing the mash temperature. one thing i'll definitely do next time is start heating up a gallon or two of water in a separate pot as i'm heating my strike water so that i have some way of correcting this if i miss next time.

the other issue is i did calculations to figure out about what the sparge water should be to get up near 165-170 during the sparges (I don't mash out, just drain). but when you miss the original mash temp that causes the sparge calcs to be off. i tried to compensate for this some but am not sure i ever got the temp to that range. however if the iodine test shows completion of conversion doesn't that mean i converted all the starches? or is it still possible that i didn't extract everything i could have from the grain?

@indigi/electric beer - ok, well the *intended* mash temp was 152. the issue was that i'm still getting used to how much heat i lose at the beginning as temperatures are stabilizing and so i'm missing the mash temperature.

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Are you preheating your mash tun? I have had a few batches where I forgot and then 20 minute into the mash I am down to 146-148, that doesnt happen when I have a quart or so of boiling water in the mlt for 20 minutes or so prior to use.

@malkore - thanks, so maybe 1.2 instead of 1.25? or even thinner? 1.1? and yes i was vorlaufing almost a gallon and pouring it back.

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I think you are going the wrong way here. 1 quart to 1 pound of grain is a thicker mash than 2 quarts to 1 pound of grain.

Do you have an Iphone or Ipod touch? If so you should really spend the $0.99 on the program Sparge Pal I've found it VERY useful on helping with my water volumes as well as hitting my mash temps. As far as sparging, I usually heat my water to about 175-180 to account for loss of heat. You can always let part of it cool and then start adding it as you go if you notice your temps getting too high.

ah ok, thanks all for the helpful feedback so i guess things i will change next brew are:

1) thinner mash (in the right direction! ) to something like 1.5 qt/lb. hopefully that helps with holding the temperature in addition to the argument about possible better conversion.
2) shoot high for my strike water temp and then let it sit for a bit to cool off to make sure my kettle and insulation are all pre-heated.
3) keep some near boiling ready to bump up my mash temp if i miss at the beginning

i'll give Sparge Pal a look too but i'm already using software to calculate the volumes so i'm not totally sure i need it. probably worth a try either way considering it's only 99 cents. it might be nice to have the numbers handy on my phone versus running over to my laptop outside the kitchen. still open to other feedback if anyone has any, but if not i'll report back after the next brew to let ya know if things turned out any better!

Mashing is a time/temp deal... not only that, but there are several enzymes in play.....

Mashing at a Lower Temp generally gets you More fermentables -- but takes way longer.... (For example -- if you want a fairly light body beer with more alcohol, mash at 140-145 for as long as it takes.....)

Mashing at Higher temps generally gets you a faster conversion, but more stuff that won't ferment..... like mashing at 155-160 gets you get a really awesome, thick, full body, hearty beer at 3% alcohol....

So.... You gotta decide.... There is absolutely nothing wrong with your mash temp -- so long as you got full conversion....

BUT... If your crush was too coarse -- you end up with a good looking iodine test and a really low conversion.... Smoosh up a sample of your mashed grain mush really good and iodine test it by itself... Hey Look... It turned pitch black...... The crush was too coarse and it couldn't convert.. Got any way to wet mill it? If not, you are left with heating the grain up to it's gelatinization temperature for a while to convert the starch and re-mashing with some more malted barley.... kinda like how you would treat an adjunct.....

Thanks

John

Are you basing your efficiency on your pre-boil SG to the OG? If you are getting conversion I cannot imagine your eff. being so low?

Just wondering!

I usually mash at about 150F. At that temperature (or lower) I mash for at least 90 minutes which gives me full conversion, and great attenuation.

-a.

KevinW said:

Are you basing your efficiency on your pre-boil SG to the OG? If you are getting conversion I cannot imagine your eff. being so low?

Just wondering!

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I'm not sure I follow what you're asking, but I based my efficiency on this: http://www.tastybrew.com/calculators/gravity.html

According to the site there my exact efficiency on my last batch was 64.2%

ajf said:

I usually mash at about 150F. At that temperature (or lower) I mash for at least 90 minutes which gives me full conversion, and great attenuation.

-a.

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Just curious...it's been my understanding that if you check with iodine you can verify that full conversion is done if it's not blue after mixing some with a few drops of wort, correct? So if I mash for an hour and then see that it's "done" from this test is there any reason I should continue to leave the mash in for longer?

neomantra said:

I'm not sure I follow what you're asking, but I based my efficiency on this: http://www.tastybrew.com/calculators/gravity.html

According to the site there my exact efficiency on my last batch was 64.2%

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Hah, yeah that is a little vague, sorry!

What I think I was getting at was the accuracy of the boil volume and your final volume. If the volume is not correct then the efficiency numbers will be way off!

Example: 8.25lbs pale malt should give you a pre-boil estimate of 1.039 for a 6gallon boil at 75% efficiency.
This should finish with estimate OG 1.045 for a 5 gallon batch. (this is from BeerSmith)

Or am I just over analyzing this way too much:cross:

neomantra said:

Just curious...it's been my understanding that if you check with iodine you can verify that full conversion is done if it's not blue after mixing some with a few drops of wort, correct? So if I mash for an hour and then see that it's "done" from this test is there any reason I should continue to leave the mash in for longer?

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You're right about the iodine test indicating full conversion of starches to something else, but continuing the mash past the conversion stage breaks down the dextrins into more fermentable sugars. I use English base malts which have relatively low diastatic power. If I mash at 150F for 60 minutes, I usually get full conversion, but I end up with a FG much higher than I want. If I extend the mash for an extra 30 minutes, I get a much lower FG and a flavor profile that I like.

-a.

KevinW said:

Hah, yeah that is a little vague, sorry!

What I think I was getting at was the accuracy of the boil volume and your final volume. If the volume is not correct then the efficiency numbers will be way off!

Example: 8.25lbs pale malt should give you a pre-boil estimate of 1.039 for a 6gallon boil at 75% efficiency.
This should finish with estimate OG 1.045 for a 5 gallon batch. (this is from BeerSmith)

Or am I just over analyzing this way too much:cross:

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Gotcha. So the short answer is I don't record the info to figure out that out exactly. I do normally use a refractometer at various points in the brew day to see how I'm doing at different stages. What I don't do is take measurements of the actual water volumes at different stages. I've only been measuring out the strike water and then the sparge water and assuming that absorption and boil off rates calculated by the software are accurate. I do have a 5g marker on my carboys but lately have been aiming for 5.5g batches.

I guess it'd be worth making a measuring stick or something to use in my kettle to figure out approximately where I'm at in terms of volume at different points of the day.

ajf said:

You're right about the iodine test indicating full conversion of starches to something else, but continuing the mash past the conversion stage breaks down the dextrins into more fermentable sugars. I use English base malts which have relatively low diastatic power. If I mash at 150F for 60 minutes, I usually get full conversion, but I end up with a FG much higher than I want. If I extend the mash for an extra 30 minutes, I get a much lower FG and a flavor profile that I like.

-a.

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Interesting...I've never had a problem to this point with too high of a FG. All my beers since switching to AG have ended at a reasonably low FG...usually between 1.008 and 1.012. In fact almost every beer I've made finishes lower than whatever recipe calculator I used expects the FG to be. I guess that's because I've always mashed low on the temp scale either intentionally ~150-152 or occasionally lower due to the issues I described in the OP.

neomantra said:

I'm not sure I follow what you're asking, but I based my efficiency on this: http://www.tastybrew.com/calculators/gravity.html

According to the site there my exact efficiency on my last batch was 64.2%

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Good, this is related to a problem I had in my first AG batch as well, so I thought I just share it here. Just brew a AG Oktoberfest for next summmer (yes, supposedly it takes about 6-8 months to get this beer in its better stage). I decided to follow Palmer's book advice for the grains I was using and did a 3-step mash (104 - 140 - 158F). Well, it was a bad idea! To adjust for those temps, I had to add a lot of water, yet, I was awlays at least 5F bellow the temps. To make things worse, my 3.5 Gal fly sparging went too fast, just 13 minutes instead of the recommneded 30-45 minutes. I ended up getting a efficiency of 65%, which I think is bad. The bad news is my beer will have something like a 3.7 ABV instead of the expected 4.7-5.2, which is not that bad. 3.7 ABV for summer while barbcueing may do the job. The good news is, my batch volume is almost 6 gallons!

Check out this chart:

How much temp do you lose over the duration of your mash? I would take measurements at dough-in after stirring like crazy in different points in the mash, and do the same when you're ready to take your first runnings.


We used a mash tun that lost 10-15 degrees over the course of an hour, most severely at the outer walls. Didn't really matter what we started a mash at, was really hard to brew anything that didn't ferment all the way dry without quite a bit of grain bill tweaking. Never really saw this having a big impact on total efficiency though.