Stir plate too fast

[mordantly]

All you need is a minor surface disruption; a 1" deep vortex is not going to make a difference according to the Pope of malt.

i think you misread my statement. i maintain 1" OR LESS for that exact reason.....

[11amas]

Ahh, IC

[beltbuckle]

And don't "test" your stir plate without liquid in the erlenymeyer. I did that and got the bar up to speed, then thought I'd see "how fast this sumbitch can go". The stir plate threw the bar... through the only-used-twice 5000mL flask. I was pissed.

[mordantly]

And don't "test" your stir plate without liquid in the erlenymeyer. I did that and got the bar up to speed, then thought I'd see "how fast this sumbitch can go". The stir plate threw the bar... through the only-used-twice 5000mL flask. I was pissed.

doh! when i got my lab surplus plate, i decided to "see" what 1600rpm does... but i surprisingly had the forethought to do it with a 2" bar on the glass top or i would have been pretty friggin mad too.

[craigevo]

I find that I have to minimise the speed so that the yeast doesnt rise up out of the flask. Especially if im doing 2l on a 2l flask.

I have just found a countdown electrical timer switch i used to use for an aquarium and am thinking of plugging the stir plate in and setting it so that it stops after say 10 hours. If a starter reaches full growth 8-18 hrs (who said that?) then 10hrs should be about enough without risking overflow at high krausen (I hope).

Im also guessing that since the yeast will still be either still be consuming the oxygen at 10 hours, this will prevent me from pitching 2L of oxidised beer into my wort ? I havent found any info on the timeframe for starters going anaerobic. - anyone know ? presumably the same as the time to reach full growth ?

One other question I hope someone can answer - If your lucky enough to have a stir plate AND an O2 tank, should you inject some O2 into the starter and then stir plate it ? is this better than just stir plate, or would this be an overkill of too much 02 for the yeast ? I dont want to bother with 02 injection if not necessary.

[a10t2]

One other question I hope someone can answer - If your lucky enough to have a stir plate AND an O2 tank, should you inject some O2 into the starter and then stir plate it ? is this better than just stir plate, or would this be an overkill of too much 02 for the yeast ? I dont want to bother with 02 injection if not necessary.

That seems like it might be a waste of O2, but I run my air pump/stone and stir plate at the same time and have seen a HUGE increase in the yeast produced. That would be doubly important if you're using an Erlenmeyer flask that's nearly full, since it would have very little surface area relative to the volume.

[whiteManCanHop]

If you do use a resistor and/or potentiometer, make sure it can handle the power. (Or use multiple resistors in series.) Most you'll find are rated 1/4 W, and you'll need 1 W minimum.

Actually you need to put resistors in parallel to be able to "add" the wattage. If you do this you also be dividing the resistance at the same time.

Series connections will increase, read add, the resistance decreasing current... but their power ratings will remain the same.

[a10t2]

Series connections will increase, read add, the resistance decreasing current... but their power ratings will remain the same.

No, it's the other way around. Resistive loads connected in series each have the same current, and in parallel they have the same voltage. P=(I^2)R. If you use two resistors, each with a value of R/2, in series, each will dissipate half as much power as would a single resistor with a value of R.

http://en.wikipedia.org/wiki/Series_and ... s_circuits