Why do I need a flask for my stir plate?

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Flask will yield better results because it looks cool ;)

Good question - I have just started doing growler starters without any type of stir plate - want to build a cheap one but don't want to get the flask. My neighbors already think I have a meth lab like it is!
 
I think you run into issues with the size of the glass between the magnet and stir bar and the shape inside the growler can come into play. Some of them are curved too much and just throw the bar
 
Some people do use growlers, but keeping the magnet balanced on the convex bottom is a PITA. The flat bottom is the main selling point of the flasks.
 
Some people do use growlers, but keeping the magnet balanced on the convex bottom is a PITA. The flat bottom is the main selling point of the flasks.

Exactly, I use 1 gallon growlers and I have a real hard tine keeping my stirbar from throwing, especially when I have 4+ quarts in there.

I have wanted to buy a 5000mL flask for a while, and my LHBS sells them for $32 but they seems to have flaws in the glass and such so I have been hesitant to drop the coin on one, especially when I can get my stirbar to keep with some patience in a growler.

Anyhow, you don't need a flask, bu they look cool, and have a practicality to them.

:mug:
 
I use 2 liter flasks, 1/2 gal growlers and one gallon jugs. I'd like to eventually get a 5 liter flask when the budget permits, but I'm in no particular hurry to do so. I use a 2" stir bar with all of the above containers without problems. IMO, problems with throwing the stir bars are usually the result of poor magnet positioning, alignment or balance. I've also learned that it helps a lot to make sure the stir plate is well leveled.

FYI, you can use a flask on an electric coil type stove if you put a wire trivet between the flask and the coil. You can easily make a trivet from a wire coat hanger or other heavy steel wire. Pyrex or borocilicate glass can handle fairly radical temperature changes, but it is not invincible. I would not push it and plunge a flask of near boiling wort into an ice water bath. I prefer to let the flask cool considerably before further cooling in a water bath. Mostly I just let the flask cool at room temp and skip the water batch altogether. I'm seldom in that much of a rush when making a starter.
 
OP - no airlock for starters, use foam plugs or foil to allow exchange of Oxygen. The Growlers (jugs in most cases) that I've used won't work with my stir plate. I'd agree with Catt that the problem is due to the magnet alignment, etc., but stir plates are generally built to spin a stir bar in a flask with a flat bottom, so I can't fault the stir plate maker for it not working with the jugs. I use a monster 5L flask and even that is sometimes not big enough to contain an explosive starter.
 
I use 2 liter flasks, 1/2 gal growlers and one gallon jugs. I'd like to eventually get a 5 liter flask when the budget permits, but I'm in no particular hurry to do so. I use a 2" stir bar with all of the above containers without problems. IMO, problems with throwing the stir bars are usually the result of poor magnet positioning, alignment or balance. I've also learned that it helps a lot to make sure the stir plate is well leveled.

My LHBS had unbranded Kimax 5L flasks for 35 bucks. It took all my self control to not buy 3 of them.
 
My opinion the biggest advantages of a flask are

it has measurement lines on it to figure out how much is in it
it is borasilicate(i think this is the right name) glass which is very resistant to thermal shock
it is clear so it is easier to confirm it is clean
it has a wider mouth and almost no shoulder so it is easier to brush if necessary

Plus the cool factor (don't all home brewers love cool equipment)
 
My LHBS had unbranded Kimax 5L flasks for 35 bucks. It took all my self control to not buy 3 of them.

I can relate to that - it takes a lot of self control not to kimax early and often.








(Sorry, I'll go now...)
 
I have a 2L version of these
41FV-w3eHJL.jpg


But then again I work in a lab
 
Jeez, you have 2L media storage jars? Even those are kind of concave on the bottoms, so not sure how well they perform on the average home-DIY'd stirplate,
 
We use em for buffer storage and stuff like that. We've got up to 10L ones, but that would be one hell of a brew to need a 10L starter!
 
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