I’m thinking of doing a brew-in-a-bag decoction mash on my stovetop for an upcoming beer. Is there anyone who’s tried it and discovered any gotchas I should know about going in?
I’m thinking of using some of our nice heavy-bottomed cookware for the decoction kettle. I’ve already anticipated complaints from SWMBO on that one. But after I used some PBW to rescue that same pot from certain death following one of her failed cooking experiments, I think I can negotiate some leeway there. 
Shouldn’t be any issues doing a decoction with a bag and you have the added benefit of being able to direct-fire the mash if the decoction addition doesn’t quite hit the target mash temp.
I do it all the time and I’m an avid BIAB’er (though on an outdoor burner). I like doing at least a single decoction on most of my beers to mash out.
Just make sure to ‘figure 8’-shape stir the decoction continually. You shouldn’t get scorching if you keep the fluid/mash matter moving.
You can’t boil the whole thing, it’ll kill all the amylase. Are you going to put malt in two bags or what?
[quote=“tom sawyer”]You can’t boil the whole thing, it’ll kill all the amylase. Are you going to put malt in two bags or what?[/quote]I assumed he meant that he was going to pull some of the grain out of the kettle and do a decoction in a separate pan just like everyone else does it.
Yup.
I’ve done decoctions with a bag several times. Basically I do “normal” decoctions (usually a double decoction personally), without a bag, and then at the very end I dump the whole mash into a bag in a bucket or spare kettle, then pull the bag to drain and continue the usual BIAB way. No need to tie all the grains into the bag at the beginning and boil the whole thing – that would be a pain and might burn holes in the bag, among other things. But yeah – decoction is easier than most people think, and even easier if you want to just dump it into a bag at the end to drain and even to sparge. For sparging, I pour hot water over the bag in a colander, or dip the whole bag into some hot water. The pouring method is tedious but it will get better efficiency, in my experience.
If you split the grist in two bags it’d seem to be easier. Digging mash out of a bag sounds like no fun. Decoction isn’t much fun period though.
