One of the major ingredients of beer is yeast. Yeast is that living organism which, in a crude way, farts CO2 and poops alcohol. It's thanks to these small guys why beer is carbonated and alcoholic. Up until now I've always used either liquid or dry yeast in my beer with no pre-processing. For liquid yeast I would use a smack pack like Wyeast or a tube of Whitelabs yeast. I'd just dump it in when it was time to pitch the yeast. As for the dry yeast, I would just sprinkle the yeast on top of the wort. After listening to the podcast Brew Strong, I've realized just how important yeast starters are.
A yeast starters is a mini-batch of beer using dry malt extract and no hops to start the yeast buildup. This is only applicable to liquid yeast. Dry yeast only needs to be hydrated in a cup of warm water. The yeast starter is made in a chemistry grade flask by boiling water, adding the dry malt extract, boiling that for around 15 minutes, then cooling. Because this is a much smaller amount of liquid it's not necessary to boil for an extended period of time like a normal beer. Also there are no hops being added so we're only doing this to sanitize the liquid.
Why this is important is to have healthy, active yeast being pitched into your beer for a quick start of fermentation. While a smack pack has around 120 billion cells, it's been found that a number more like 150+ billion is closer to the amount needed. An easy way to figure out the amount of yeast needed is to use Mr. Malty's calculator. While listening to the podcasts they talked about stiring the yeast starter often, or using a stir plate. A stir plate is essential a spinning magnet which spins a magnetic bar which can be placed into a chemistry flask or other container which is set on top of the stir plate. Yeast require food (sugar) and oxygen to build up their numbers, hence why stiring is needed to keep a healthy flow of oxygen. I figured if I'm going to start building yeast starters, why not go all in.
After doing some internet research I found the stir plates are really damn expensive ($75~$100+ range). I did however find this website which talked about building your own stir plate. After looking at the items required to build this, I realized I had most of what I needed already. I have a lot of extra computer parts, connectors, and wires which covered my need of a computer fan and the rare earth magnetic. I had a box I could have used but I made a trip to my local Ax-Man Supplies store for the box and some additional items. For those of you not from the Minneapolis area, Ax-Man is a store full of random shit. There's really no better way to explain it. It's like an army surplus store but with more random motors and tinkering items. It's the perfect store for that school science project. So for $14 I bought the rest of the items I needed, along with a few extra goodies I might use later.
Note the pint glass in the background :)
One thing that I did different was I didn't screw my fan to the box. I didn't want my $27 flask resting on some bolts so I used motherboard plastic standoffs which I glued to the lid of the box. For $14 I think it works pretty damn well. Additional costs were $27 for the 2000ml chemistry grade flask and $6 for the 1 inch stir bar. The guy at Midwest supplies talked me into the 1 inch stir bar, though I'm starting to think I maybe should have bought the 2inch bar. Here's a video I took this morning of the first test run. You'll see in the video I change the speed of the fan using the control knob. Overall I'm happy with the project and I'll post updates as I build my first yeast starter. If you're interested in building your own stir plate, feel free to contact me.
Prost! -Ryan
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