June 24, 2016 by fhsteinbart
When I first started home brewing, I usually and customarily used dry yeast as it was convenient, easy, and cheaper than the glass vials of liquid yeast that were around back then. While I tried those vials on occasion, they were rather hit or miss as the quality left something to be desired in the fermentation department. So when I got a bottle of beer with yeast in the bottom, I was intrigued with the idea of culturing it up. So I got a couple of tablespoons of DME, and made a 6 oz. wort to which I added a pinch of yeast nutrient and dumped it into a recently opened bottle of beer. Then I flamed the orifice of the bottle and then pushed in a stopper with airlock (they were cork and glass back in those days), and left it in my parents’ kitchen for a few days. After about a week, I was rewarded with about a quarter of a cup of fresh yeast to which I added it to a half gallon of wort in a gallon jug and got my starter for the next batch I was going to brew.
So for you to make up a beer bottle starter, all you really need is a bottle of beer with yeast sediment, some DME, a small funnel, a butane lighter or gas stove, a #2 stopper with an airlock hole, and an airlock. Additionally, you need to make sure that the yeast in the bottle is from primary fermentation as not all breweries use the same yeast for refermentation in the bottle as they do for their primary fermentation!
Second thing that you need to do is test for viability. Live yeast will take up methylene blue, while dead yeast will not, so the number of blue cells will give you an idea of how many cells are actually alive and well. You can get a reasonably priced student microscope for under $100 these days, and disposable hemocytometers and cover slips can be had for less than a buck apiece. Finally, you need to grow up an active culture of yeast that’s adequate to do the job ~ about a ½ cup will do for a standard gravity ale. Live yeast in the bottle can be very rewarding, or entirely frustrating, depending on whether or not you have the actual yeast from the primary fermentation. So go out and explore the unexplored country of the yeast beer o’ scape!