advice on BIAB mash temps

[DrummerBoySeth]

I have been an extract brewer for more than a year with several extract batches under my belt. I got a 2 gallon fermenter for Christmas this past year, and I am excited to try my first BIAB/all-grain batch. Before I commit time, money and ingredients to my first BIAB, I decided to do a "test-mash" to see if I could hold mash temps for one hour in the oven.

I have a fairly modern "digital" oven. The lowest setting is "warm", which is supposed to equal 170 degrees.

I preheated the oven to "warm" and heated 1.5 gallons of water in my regular brew pot to 148 degrees. I then put the pot in the oven with my brew thermometer in it, and checked the temperature every 15 minutes for one hour. My results were as follows...

148 degrees @ 0 minutes (start test)
148 degrees @ 15 minutes
149 degrees @ 30 minutes
150 degrees @ 45 minutes
151 degrees @ 60 minutes

Does anyone have experience with a mash schedule like this? Would temperatures like this even work? Should I turn the oven off at the 30 minute mark to keep the temps from rising too much during the mash? Would the added volume of the grain bag change the rate at which the wort temperature increases, negating the whole problem? I am familiar with the general effect of mash temp on the wart fermentability, but what effect would this slight increase in mash temps over the course of the mash have on the resultant beer?

Anyone with experience/ideas that relate to this, PLEASE feel free to set me straight. I really want to try this all-grain thing, but only if I can do it well. I already know how to make REALLY GOOD extract beer, so I am not willing to go backwards with quality just to say I am an all-grain brewer. Help me make this transition the right way!

 

[fatnoah]

I've only done 1 BIAB batch so take my advice with a grain of salt. But what I did was heat my oven to 200 while I was bringing my water to strike temp. After doughing in and making sure my mash temp was right I turned the oven off and put the pot in the oven. The mash stayed within one deg. for 60 min.

 

[ChrisL_]

I have only done one batch as well but was concerned with holding the temp in an aluminum pot. I mashed in and was one degree over my target then I just wrapped my pot in two old blankets and it only dropped to one degree below by the 60 minute mark. More then close enough. I recently found some of the insulating wrap I used on my hot water tank and plan to make a "cozy" for my pot for my next batch to see how that does.

 

[DrummerBoySeth]

That may be similar to what I try to do next. I plan to re-test my ability to hold mash temp by retesting the system and shutting the oven off after 30 minutes. I would "mash in" at 148 degrees, place pot in preheated oven, shut oven off at 30 minutes, and check the temp at 1 hour. This SHOULD do a better job of maintaining the temperature than the first test.

I guess my real question is... If I am unable to improve my system and maintain temperatures more accurately than my first test, what effect will the 2-3 degree increase over the course of a one hour mash have on my efficiency/fermentability?

Also, should the mash be stirred at all during the one hour mash time, or should it be left alone for the entire hour? It seems like a gentle stir halfway through the mash would help to increase efficiency. Is this just an illusion? Again, I just want to get this right.

 

[fatnoah]

I'm not sure if stirring helps or not. But I took mine out of the oven after 30 min. to check the temp. and give it a stir. My efficiency was great and was actually over my estimated pre-boil gravity by 3-4 points.

 

[aiptasia]

You would have issues with your saccrification, and therefore your efficiency would go down. That being said, Stone brewing mashes at 148*f on their ales for a lighter, crisper, less body beer. Depending on the style, the happy medium for proper conversion seems to be right around the 152-153*f range using 2 row as your base malt.

I would not trust the temperature readout on the oven if that's what you're using to monitor your temperatures. You don't know how accurate it is (when did you last calibrate it?) and it won't measure the temperature of the mash itself, which is what you need to monitor. The constant opening and closing of the oven to check temperatures also loses heat. Remember, when you mash in, your strike water temperature is going to fall by about 10 degrees F.

Most of my recipes are BIAB stovetop. I'm very patient and exacting and use a long metal probed meat thermometer with a calibration screw. Once calibrated, I can measure temperatures with it within half a degree accuracy. It has a metal clip on it so I clip it inside my pot. I mash in at 162*f and I make very sure the temperature is stable at that temperature for at least five minutes before adding the grains. Usually, i'll mash for 70 minutes for two row and other grains like vienna and munich that require mashing right in that sweet spot of 152-153*f. This gets me a little better efficiency as I do "no sparge" BIAB. I just let the brew pot sit right on the stove on a low setting and check the temperature every few minutes to make sure it's dialed in.

Specialty grains get a 45 minute pre-mash steep n a grain bag unless they're really dark roast (chocolate, black patent, anything over 120 lovi). I used a new technique with a recent imperial stout brew that involves doing a cold water steep of dark roasted grains to avoid harsh tannin and other astringency contributors. As their sugars are completely converted, these grains can easily be soaked in water for their sugars. Two quarts per pound soak for 48 hours prior to the brew day in distilled water did the trick. This grain tea then gets re-added back to the boil at 10 minutes to flameout. No tannins, no astringency.

 

[wilserbrewer]

I plan to re-test my ability to hold mash temp by retesting the system....

Be advised that a mash will hold temperature much better than water, that being said, a warm oven will hold your mash at an acceptable tolerance, a couple degrees doesn't mean very much in reality.

If I were you I would start collecting data while brewing rather than conducting experiments with water...a warm oven will work fine to keep mash temps "in range".

 

[Ogri]

^^^^^^^

I've only done a couple of batches of AG/BIAB so far. The first was done using thermometers that were a bit dodgy to say the least and turned out great. I, as well as a couple of beer aficionado mates, was really surprised and pleased with how well it turned out.
For a two gallon batch you're not talking about a huge layout for ingredients so just give it a whirl and I'm sure you'll get an instant boost in confidence. AG has a stigma of difficulty that doesn't really need to be attached. There are, however, numerous avenues of complexity to explore if you wish to explore them.

 

[nutty_gnome]

Yeah... you are overthinking it. If you want to worry about temp swings, look at your fermentation set up and try to hold that constant; steady ferm temps are more important than a 3 degree uptick in mash temps over an hour.

 

[Psych]

Yeah... you are overthinking it. If you want to worry about temp swings, look at your fermentation set up and try to hold that constant; steady ferm temps are more important than a 3 degree uptick in mash temps over an hour.

Agreed, 4 degrees over an hour is fine, start 2 degrees below where you'd want and you'll only be 2 up after. But probably with all the grain in there you'll see even less change.

If concerned, shut the over off halfway as you suggested, it'll be totally fine either way

A change this small will have practically zero effect on the final product, contrary to what you might read that a 1 degree difference will mean a completely unfermentable wort or something crazy. I've mashed between 145 and 155 with virtually no final product differences, at times.

 

[cadarnell]

im a lucky one with an oven that has a setting of 150 ... but i still shut it off half way thru the mash ... if i had a 170 setting i'd probably shut it off a third of the way thru ... temps going up bother me more than temps going down ... good luck and cheers !!

 

[MMJfan]

Agreed, 4 degrees over an hour is fine, start 2 degrees below where you'd want and you'll only be 2 up after. But probably with all the grain in there you'll see even less change.

If concerned, shut the over off halfway as you suggested, it'll be totally fine either way

A change this small will have practically zero effect on the final product, contrary to what you might read that a 1 degree difference will mean a completely unfermentable wort or something crazy. I've mashed between 145 and 155 with virtually no final product differences, at times.

I agree. From my experience, swings in fermentation temps will impact the final outcome of your beer more than a couple of degrees up or down while you are mashing. If the recipe I'm using calls for a mash temp of 152 and I'm only at 150-151 after adding my grains to my strike water, I'm not going to sweat it...

 

[DrummerBoySeth]

Thanks for all the replies, everyone. I really appreciate it. I have got fermentation temperature control down to a science now, so I do not need to worry about that too much. It is because I feel comfortable with all the other aspects of brewing that I wanted to make this move to BIAB. It seems that most of you agree that the slow increase in temperatures is not a big deal, so I will probably not worry too much about that. If it looks like it is climbing too much or too quickly, I will just shut the oven off and hope for the best. Thanks again!

 

[Ogri]

Something else to bare in mind, that I've seen written a few times on here, is that sometimes conversion can be pretty much over in the first 15 minutes or so,

 

[kevreh]

Specialty grains get a 45 minute pre-mash steep n a grain bag unless they're really dark roast (chocolate, black patent, anything over 120 lovi). I used a new technique with a recent imperial stout brew that involves doing a cold water steep of dark roasted grains to avoid harsh tannin and other astringency contributors. As their sugars are completely converted, these grains can easily be soaked in water for their sugars. Two quarts per pound soak for 48 hours prior to the brew day in distilled water did the trick. This grain tea then gets re-added back to the boil at 10 minutes to flameout. No tannins, no astringency.

That sounds like a good idea to cold steep them. Reminds me of cold steeping coffee for iced coffee.....a lot of flavor but no bitterness.

 

[Calichusetts]

Two points:

Grab an Ice Cube cooler if you can...I got two and they are amazing! Keep them in my basement which is constant, then in the cooler, perfect. You can also take out bulkhead in the back and easily set up a heating/cooling fermentation bucket.

Definitely use the oven if you can. I was pretty set in my ways last year and made a resolution to take some risks (technique-wise, I already go crazy with experimental brews) and they have paid off. I actually mash in the pot directly but strain through a paint-strainer and do sparge mash in the bag. Much clearer beer and a 7% efficiency bump (78% now) The warm setting on the oven is amazing. Turn it on while you heat up the strike water then turn it off when you put it in. No change in temp. I checked it every 15 minutes the first time (because I can't leave anything alone) and every time it was constant. If you take it out to stir just put the oven back on warm until you put it back in.

 

[iancl]

Living some place warm? dough in and once you are happy with your temp, just wrap it up in a towel and then a blanket, and then cover the whole thing up with a plastic trash can and leave it alone. I usually lose less than 1-2 degrees over an hour. Mash is thicker than water., and tends to hold the heat.