Hey there B'n'B and welcome to the forum
Clever thinking and beautifully written instructable - see end.
I'm going to jot a few notes down for you one which you probably already know and one which you won't...
1. Don't be too lazy when starting out. Never hurts to give the mash a stir and check its temp during the brew a few times as this gives you a good idea of what is going on with your equipment.
2. In your instructable, in the first paragraph, you've written great stuff about BIAB but there is one major error. Let's have a look...
The 'brew-in-a-bag' (BIAB) homebrew method is great. It means you can brew all-grain beer using just one pot! But this also means you can't mash in ideal containers such as insulated coolers and the like, so keeping your mash temperature constant can be a challenge.
A full-volume mash in BIAB of say a 19 L (5 US gallon) Volume into Fermentor batch actually works better than an esky / cooler. The reason for this is all the water goes into the mash so the rate of cooling loss is very low in most climates. In an esky, with traditional brewing, you have a small volume and no way to heat the mash. What happens in an esky is you have a lot of pockets of heat and cold and, of course, it drops in temperature a few degrees at least on that size mash.
In 19L/5G VIF batch, you also have the option to apply heat during the mash so, in reality you have a system that loses heat very slowly and whose temperature can be maintained very easily.
Just thinking that maybe the word stovetop should be added in the title of the instructable
In stovetop BIAB brewing, you are doing a very small batch size so you have less thermal mass and controlling temperature is trickier but it is still better than a three-vessel system of similiar output
. You are using one 19 L pot probably. If you went three vessel,you would need a 12L esky (which would be crap for holding heat) and your 19 L pot.
So, you are still mashing in an ideal container in stovetop BIAB, it's just that the small scale of things makes maintaining mash temp more problematic. BIAB is irrelevant to this.
Another trick for maintaining mash temp in stovetop brewing can be to put the pot in your oven if your oven is sensitive enough.
I hope you don't mind me making the above point/s but as I said in the beginning, that was a beautifully written instructable you wrote so it might as well be totally error-free. I hope we get to see you contributing stuff like that here. Excellent
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