Acceptable mash tun heat loss

[Oh Crap]

I was rcalibrating my system before sat's brew day, my mash tun is a converted keg and is insulated using heavy underfloor insulation... i is also direct heated(if necessary)
It lost 4c over 60 mins without heating... Is this acceptable or too much? I can always fire up the gas if it's too much but if it's acceptable then not using gas saves money for more stuff

[Parky]

Different enzymes work within different temperature ranges to convert the soluble starches in the mash to fermentable sugars. Beta Amylase and Alpha Amylase are the two enzymes that are of interest when converting starch to sugar, and work well in the range of 64.5 - 70^oC (although Beta Amylase taps out around 66.5^oC). See image below -



So when you ask if 4^oC will make a difference it all depends what your starting temperature was. For example, if you started at 68^oC and dropped to 64^oC, you will be well within the range for Alpha Amylase and should have a good enough conversion.

You must remember that the goal of a mash is to convert all the soluble starches to sugars. To determine if this has happened you can perform an iodine test, and if you find that the starches have been converted then it's job done, regardless of the ups and downs of the mash temperature. You can also use programs like Beersmith to calculate the efficiency of the mash to determine how the enzymes performed.

Usually I check the temp of a 60 min mash every 15 minutes and stir. If the temp has dropped I add boiled hot water to compensate. With my system an additional 750 ml of boiling water raises the temp by 2^oC, and you can determine what works for you doing this over a number of batches.

At the end of the day it's all about getting those starches converted, no matter how you do it 

Some additional reading here that might be of use -

http://www.jaysbrewing.com/2013/01/16/6-different-mash-rest-that-improve-your-beer/

https://byo.com/stories/item/1604-what-mash-temperatures-create-a-sweet-or-dry-beer

[Oh Crap]

Cheers parky, that answers any question I might have had about this. At least now I can allow for differences

[molc]

I'm now having the issue that I'm trying to make 12 litres batches in a 45 litre mash tun, so the mash goes from 66 to 61 over the hour since I have such a low volume of water in the run.  Going to try mashing thinner but it's a real pain to hold temp.
Starch test comes out ok though, so it's more a question of how sweet/dry the wort will be.

[Parky]

@molc - just an idea, but you might try starting the mash a little on the thick side, say 2.2L/kg, and add an extra 0.5L/kg of boiling water over the duration of the mash. This may not compensate for the total temp drop, but it might keep things within a couple of degrees of target temp. Sounds like it'll be tough to maintain consistent temps with that set up no matter what you try 

[molc]

@parky: Did that the last time and it just ended up losing as much heat by opening the lid

[Simon_]

I'm now having the issue that I'm trying to make 12 litres batches in a 45 litre mash tun

If you've a ~15 Litre pot and biab bag you're all set. Stick the pot in a preheated oven at roughly your mash temp and it won't waiver. Small batches are perfect for stovetop.

[molc]

I'm now having the issue that I'm trying to make 12 litres batches in a 45 litre mash tun

If you've a ~15 Litre pot and biab bag you're all set. Stick the pot in a preheated oven at roughly your mash temp and it won't waiver. Small batches are perfect for stovetop.

Yup, that looks like what I might need to try. Alas, the smallest I have right now is the 28Ltr boiler.

For the next small brew, I'm going to skip the mash out and put all the water in at the start, which hopefully should reduce the airspace heat loss.