I put some WLP002 English Ale yeast (whose provenance is reportedly the Fullers brewery of Chiswick, London) on my rickety home made stir-plate last night in preperation for a batch of my house real ale tomorrow. This is a highly idiosyncratic yeast. Most yeasts will take a few hours – or even days – to flocculate (clump together) and settle to the bottom. As you can see from this video, this yeast forms into chunks before it’s even hit the bottom of the jar. This can lead to problems; the yeast can sometimes under-attenuate and drop out of the beer before it has finished, leading to a sweet, worty tasting beer. This can be overcome by giving the yeast a gentle rouse each day. The up-side is it leaves a brilliantly clear beer, perfect for cask ale. I like this strain in particular for lower gravity beers (lower than, say, 1.040) because it leaves a slight residual sweetness, rounding out the body of the beer.
The stir plate itself was knocked together in ten minutes out of balsa wood, nails, an old PC fan and some magnets, costing under a fiver. Sure, it’s as ugly as hell, but it does the job. For an explanation of the benefits of stir plates, have a look at this link. I’m convinced of their efficacy, anyway. The video shows a nice thick layer of yeast which was cultured from a tiny sample that has been stored in my fridge for several months.