So after a recent post I have decided to do a few 1 gallon test batches. So I was curious if I could brew in a 5000 ml Erlenmeyer with good results, the only thing that i could think of is the shape of the flask. It is pretty much an upside down conical and since conicals where designed for optimum fermentation that makes me think that it may not be great. On the flip side the flasks are used for starters. So I’m slightly confused, if anyone has experience please chime in.
Thanks!!
Are you thinking boiling and fermenting in the flask? For a 1-gallon batch, I’d think the 5L wouldn’t be big enough for the boil. As for fermentation, it could probably work although you’ll probably want to set up a blowoff tube.
Oh, and the conical shape is primarily to facilitate yeast harvesting and trub dump - neither of which you need to be too concerned about.
The advantage to the conical shape is that it makes it easy to draw off trub and yeast that settle to the bottom. The yeast don’t care about vessel shape unless it will somehow change the pressure. And on a homebrew scale it’s not something to worry about. So ferment away in a 5 l erlenmeyer.
Perfect that’s what i wanted to hear. Thanks a ton guys!
And yes i was thinking of boiling and fermenting in the flask, one gallon is 3785ml so that would leave me (I think) enough head space for boil and krausen. I will use a blow off tube regardless.
just use some Fermcap and you need not worry at all about boilovers, and maybe not about the blowoff - tho I’d still be ready given the geometry.
I would be worried that even with FermCap you will have boilover when you add hops.
Have you ever clean a boilover on the stove? 
ah - forgot about hops - was thinking of when I make starters, but there is not hops - good point.
yes I have (starters prior to Fermcap) and I got the same comment everytime - “I thought we had all that equipment in the garage so that you didn’t have to make a mess in the kitchen!”
Don’t forget that, to end up with a 1-gallon batch, you’ll need to start with more than 1-gallon pre-boil to account for the boil-off/evaporation.
+1. I wouldn’t try boiling the batch in the flask. Boil in a pot and transfer to the flask then give an ice bath. Hell, save yourself a lot of time and trouble and just drink it from the flask too. No since bottling 1 gallon, is there? 
It’s easy!
I boil 4500ml in my 5L flask all the time. Two drops of FermCap works wonders for starters.
A lot of good points here, I’ll just do the boil in a pot and transfer to the flask while hot, although what about break material should I use a strainer to catch the hop/break matter?