Stir bar advice

[roger the dog]

I've just splashed out on a second hand stir plate from Ebay & I was wondering what size stir bar I should get, I'll be using a 1 gallon demijohn.

I've seen this one but thought it might be a bit small, what do other HoneyDew Bunsens types around here use ?

[jubby]

I think the biggest you can fit in your jar/flask is best. I don't use demijohns but i believe they have a curved bottom and one of those stir bars would not sit right. How about one of those dumbbell shaped stir bars? There may be demijohn users who can advise you better on the type of stir bar to use.

[Scooby]

The ends of the bars are the poles of the magnet. With this in mind I chose a bar with a length that positioned them over the rotating poles in the stir plate. Not sure this is the correct way but is logical.

With regard to shape there are two main designs, dumbbell and ridge in the middle, the dumbbell is for viscous liquids where a ridged one might get 'bogged down', I'm not sure it really matters which one you use.

[roger the dog]

Thanks for the advice, I decided to get one of each type in the end & the dumbell one works the best, I can't seem to couple the other type with the stir plate magnet to get it started