To be honest, a stir plate is one of the most important pieces of homebrewing equipment you can invest in, along with a 5000 ml borosilicate flask.
The erlenmeyer flask doesn't have to be that big, but when you start making high gravity beers, such as barleywines, wheat wines, etc., you really need a huge yeast starter so the yeast won't get stressed out trying to ferment so much sugar to such a high alcohol content.
Most beginning homebrewers, and many more advanced brewers, don't pitch enough healthy yeast. Making a yeast starter will help you grow much higher cell counts, ensuring a more healthy yeast that will out-compete all other organisms in your fermentation.
Not only that, a good healthy pitch of yeast will lower the risk of infections, make better tasting beer, and increase the speed at which the yeast ferment to completion.
Stir plates are everywhere now. You can purchase them very cheaply or make your own. It is a fun project and you don't need to be a Mr. Peabody to make one.
A lot of people sell stir plates, and there are many cool ones online. I purchased three or four on ebay until I found one that actually worked like I wanted.
But they are very simple to make. The only skill you really need is to be able to solder. I found a pretty good video on youtube which will give you the confidence you need to build your own stir plate.
When making my starters, I noticed that the stir plates were getting pretty hot and were most likely transferring the heat to the starter. I also had a problem on one stir plate that would vibrate making the flask move around, sometimes getting too close to the edge.
I'm sure not all stir plates have this problem, but I bought a heavy duty laboratory stir plate that really put out some RPM's.
The solution I came up with was to use one of my silicone hot pads on top of the stir plate (as seen in the image above). They are heat resistant to 675°F (357°C) thus providing some thermal insulation and a great skid resistant surface to keep the starter in place.
The raised dots on many styles of silicone hot pads allow air to flow under the flask to keep it from getting too hot.
The silicone hot pad doesn't interfere at all with the magnetic action of the stir plate, and can be cut to any size. All in all a pretty simple solution to my problem and is a good DIY brewing gadget.
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