One thing you might hear about as you get further along into homebrewing is the need for a “yeast starter” or “pitching rates.” Below 1.060 gravity you can still get away with a single smackpack or vial of yeast and end up with a fermentation that finishes and has enough oomph to clean itself up afterwards. But when you start looking into big Imperial style beers, barley/wheat wines, Double IPAs, etc a single serving of liquid yeast is simply not enough yeast to finish off such a big plate of sugar. So now we need to make a starter!
For a typical big beer between 1.060-80 you will need at least a 1-Liter Erlenmeyer flask and you will need some DME (Dry Malt Extract) and you will need to brew up the DME for 1.040 of yeast starter goodness. You need about 10g of DME per 100mL of starter so 1L will come in at 3.5 oz of DME boiled in 1L of water for about 15-20 minutes. What I like to do is get the water boiling in the Erlenmeyer flask to sanitize it and then carefully pour the boiling water into a saucepan and boil the wort with the DME. Once you have boiled the wort pour it back into the Erlenmeyer flask and chill it down like you would if you were brewing a small beer. An ice bath in the sink will suffice. This is why I put the wort back into the flask because I have found that the flask fits easier in the sink than a saucepan with a handle.
You can spend upwards of $100 for a cheap stir plate or even more for a professional agitation unit OR…. You can build your own for anywhere between $15-30.
I just recently built one using this video as inspiration:
The one place where my build differs from Fo’s is I used a Thermaltake Mobile Fan II External USB cooling fan for the magnet mount. This somewhat limits where I can plug in my stir plate as I don’t have a laptop but I didn’t feel like splicing the wire. Splicing wire is not hard at all but I’m lazy and just felt like going the USB route and it works great. Make sure you have a variable control for your fan RPM however. When you first plug in/turn on your stir plate with your suspension in place the bar may not move right away and you will need to slowly increase the rate of spin to get it turning, taking care not to “throw” the stir bar. Once the bar is turning you can then turn down the RPM if you so choose or leave it where it is. As far as I know the speed at which the bar is spinning has little to no effect on the actual process. So long as you are agitating the yeast cells and keeping them from flocculating and settling out, your stir plate is doing its job.