Magnetic Stirrer

[a1149913]

Hey guys, i've got a magnetic stirrer going but i'm not sure if its getting the job done. I've currently got a 7-800mL starter in there but it doesn't seem to pull the vortex all the way to the bottom of the flask. Is this going to limit the effectiveness?The stirbar is quite large, probably 40-50mm, should i try a smaller one?

Thanks

 

[felten]

It doesn't need a vortex all the way to the bottom, a dimple in the top of the liquid is enough. It just has to be moving enough to keep the yeast in suspension and knock out some co2.

 

[a1149913]

Thanks

 

[Malted]

Generally speaking, I have found that that the vortex will not go AS FAR down when the specific gravity is high but once fermented the vortex will be larger.

 

[a1149913]

Generally, how long should it take to finish fermenting? I pitched a swollen 2124 liquid pack into 700mL starter on sat arvo and its been stirring since then but i haven't had any Krausen formation. The temp is probably around 17-21. Would this suggest no yeast activity or just an attribute of this yeast?

Thanks

 

[kevin_smevin]

Generally, how long should it take to finish fermenting? I pitched a swollen 2124 liquid pack into 700mL starter on sat arvo and its been stirring since then but i haven't had any Krausen formation. The temp is probably around 17-21. Would this suggest no yeast activity or just an attribute of this yeast?

Thanks

It would have fermented out in 12-24 hrs. Probably more like 12. You wont see any krausen formation with stir plate as the stirring stops it forming. An quick easy way to check if its done is turn the plate off. The yeast will settle very quickly if its finished. If it's still eating sugar it will not drop out but keep the solution milky looking

 

[argon]

That's the thing about stir plates... sometimes it's hard to see signs of fermentation. Sometimes i'll get a nice little foamy head on the stirring wort and sometimes it's as flat as a mill pond. Often the motion of the stirring will kill the krausen.

Experience tells me that for a small step like 700mL it'll all be done and dusted in less than 36hrs. Then step that up to whatever size you want and pitch after chilling and decanting after about the same time.

 

[a1149913]

excellent, thanks a million!

 

[Wolfy]

It would have fermented out in 12-24 hrs. Probably more like 12. You wont see any krausen formation with stir plate as the stirring stops it forming. An quick easy way to check if its done is turn the plate off. The yeast will settle very quickly if its finished. If it's still eating sugar it will not drop out but keep the solution milky looking

Good advice, and agree with what you said ... except for the bit about the stirring stopping krasuen forming:

While it's true that for some/many people - especially when using smaller starters - you'll not see any visible fermentation activity/krasuen, it seems to depend more on the individual situation/yeast etc than being a fixed rule.
As long as there is yeast growing (which you can see when it settles after the stir-plate is turned off) it does really not matter what it looks like, but to make things easier, I generally keep my starters on the stir-plate for 24h.