4Apr/110

Building a stirplate

I recently started acquiring everything I need to be able to slant and propagate yeast. I’ve never used liquid yeast before, so the first order of business was building a stirplate to be able to step up slants and make starters.

Stuff you need

  • A fan – Many people use 12v 120mm or 80mm computer fans
  • 1 or 2 strong magnets. I used one from an old hard drive, and some epoxy to attach it to the fan
  • 12v power supply (wall wart) Make sure it is at least 500mA, preferable 1A.
  • Project box – make sure it’s large enough to hold the fan + components. You can get a cheap tupperware box from somewhere, or you can go fancy and buy an electrical box from eBay or radio shack.
  • For the speed controller (optional, but recommended):
    • 10k linear potentiometer, 1k resistor, 1uF electrolytic capacitor, 0.1 uF ceramic capacitor, protoboard, LM317 voltage regulator
  • You’ll also need some tools to assemble everything, f.e. soldering iron, drill, screws, glue and a few screws

Let’s start with the speed controller

I followed the instructions from here to arrange the components on the protoboard. In retrospect I should probably have gone with a PWM speed controller in order to have greater flexibility with setting the speed. Maybe next time.

As for assembling everything in a project box, a picture is worth a thousand words:

Depending on what box you will pick your mileage may vary. I used 4mm machine screws to mount the fan, and a couple of bolts to secure it:

The main concern with assembling everything is centering the magnet(s) on the fan. What I did was get some silly putty, put on the fan hub and fastened the magnet with that. Then turn the fan on (on low speed) and check for vibrations. Repeat until vibrations are virtually gone. When the magnet is properly centered, turn on the fan and mark the center of gravity on the magnet with a pen, like so:

Then just remove the silly putty and fasten the magnet with epoxy or other strong glue.

This is my finished stirplate, ready for making starters:

I have a 1000ml Erlenmeyer flask in the video, but it works equally well for 500ml and 2000ml flaks. The stirbar I got is 1 3/8″ long and teflon coated. I got it from austin homebrew supply.

I hope this post proves helpful for someone trying to make his/her own stirplate.

Next on my yeast propagation todo list

Before I’ll be able to make yeast slants I have a few more things I need:

  1. Buy a pressure cooker to sterilize everything, including yeast slants
    1. I ended up buying a Fagor Splendid 10-Quart pressure cooker
  2. Buy some yeast to use. I’m thinking I want to do a wit beer, some kind of belgian trappist and more. There are no home brew stores in Iceland that sell liquid yeast, so I will have to order from abroad and cough up some cash for express shipping and cold packs

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