Monday, 14 June 2010

Green Bullet Gold Yeast Count

As promised, I did a yeast count on the Green Bullet Gold.  For this I used a plastic container to hold my sample, a pipette, a hemacytometer and a microscope.  I just take a small sample of the beer, a few ml, from the sample tap on the FV.  I then draw a load of it into the pipette and squeeze it back into the sample a few times.  This helps to break up any clumps of yeast and also degasses it.

The hemacytometer is a thick glass slide that has two chambers each holding 1/10000 of a ml.  These chambers have an accurately grid etched into them which effectively allows you to count the cells in a known volume of beer. I take the coverslip and plonk it onto the hemacytometer so that it covers both of the chambers.  Then I draw a small quantity of the sample into the pipette before squeezing until a droplet is hanging off the end of the tube.  This droplet is then offered up to the edge of the cover slip where it is drawn ito the chamber.  I repeat this on the other chamber.  Take a look here to read more about how to do it.

Actively fermenting beer has about 60,000,000 cells per ml but as the fermentation subsides this reduces and the yeast drops to the bottom of the FV.  At racking you're looking for there to be about 1,000,000 cells per ml.  At this point there's enough yeast to ferment any priming sugar to carry out the secondary fermentation without causing excessive bottoms.  This means the cask will settle quicker and bottles will just have a film of yeast in the bottom rather than a thick sludge.

So, in my Green Bullet Gold I have 890,000 cells per ml which is typical of WLP002 or Fullers yeast.  It drops like a stone.  Based on this I'll set the FV temperature controller to start cooling in the morning and will rack to cask on Wednesday evening.


  1. Do your secondary fermentations cause "excessive bottoms" then?

    Oooh, nasty! ;-)

  2. I would have expected better of a lady ;o)