Stir plate getting too hot for the starter?

[RobertHSmith]

I purchased 2 used corning pc-353 magnetic stirrers from ebay after the second of my home made stir plates started stalling when left on overnight. Both get warmer than I would like when left on for an extended period of time, one gets to around 82 deg. and the other 91 deg.

I am using hot pads from the kitchen to insulate the starters from the stirrers for now, but I am thinking that that isn't going to be the best solution long term. With my home made plates I would cover the stirplate and the erlynmeyer flask with a towel to keep it warm and to keep the sun off of it. I'm worried that if I use a towel with these corning stirrers that it will kill off the yeast.

Any suggestions as to what to use as an insulator betwee the stirrers and the flasks? The magnets that the corning stirrers use will stir the 2" bars I have with ease, even when spaced between .75 - 1" from the plates surface.

I was thinking of using a piece of stryfoam, but was also thinking that having some sort of air flow between the flask and the top of the stirrers.

Has any one with commercial type stir plates solved this issue?

 

[TipsyDragon]

the heat reported is not going to kill the yeast. most microbes are good below about 130F or so.

 

[fratermus]

I purchased 2 used corning pc-353 magnetic stirrers from ebay after the second of my home made stir plates started stalling when left on overnight. Both get warmer than I would like when left on for an extended period of time, one gets to around 82 deg. and the other 91 deg.

My homemade stirrer runs cool, and my (unheated, I've read the specs) Fisher Scientific commercial plate runs hot like yours. I've handled it a couple of different ways:

* with a thin slice of styrofoam as you discuss. Sacrificed a Bud Light cooler I found in a neighbors garbage and filleted it to desired thickness.
* suspending over the stirplate using a lab stand and rubber-fingered gripper thingy (pardon my technical jargon!)

Of the two I think the foam is as effective but much easier and space efficient.

 

[Brew-boy]

My home made stir plate ran hot as well. The box is a Radio shack project box a black 6x9 I think. I fixed the problem by drilling a few 3/8 size holes in the side of the box to let warm air out, problem solved now.

 

[david_42]

Higher temperatures are not a problem during the growth phase and those are not all that high.

 

[jds]

Personally, I'd let it run warm and decant to get rid of the stale, estery, oxidized leftover beer.

However, if you want it to run cooler, why not use a couple of chopsticks as standoffs from the stir plate so you get airflow around the bottom of the flask?