I have been brewing for years and I did not realize until just recently that liquid yeast packs (or vials) become increasingly ineffective as they grow older.
I was reading some articles the other day and one of them mentioned that if you buy a yeast pack that was produced on that very day you can only expect about 97% of the yeast cells in the pack to be viable. If the yeast is a month old it is only about 75% viable. If you are brewing a strong beer with old yeast (or even a somewhat strong beer) you are probably going to need either a second packet of yeast or you will need to make a yeast starter to build up a sufficient count of yeast cells to tackle the strong sugars in a high-gravity wort.
When I stopped at the home brewing supply store last night to pick up yeast for my next batch I paid attention to the production date on the yeast. I was a little bit annoyed that the newest packet in the style that i needed was a month and a half old. There were some packets that were almost 3 months old. It was a strain that was somewhat less common that other brewing yeasts, but still…
I have experienced under-attenuated batches of beer in the past, and this might be why.
In any case, there is a pretty handy calculator at MrMalty.com that helps you determine how many packets of yeast you need under different conditions.
Have you ever experienced any problems with brewing yeast?
One of the easiest ways to improve your home brewing supply arsenal is to buy a wort chiller. This allows you to skip the ice bath for some equipment that will cool your wort faster and with lower chance of infecting the beer.
There are three types of wort chillers:
1. Immersion Wort Chiller
Immersion chillers are copper tubing wound into a cylindrical shape. You place the tubing in the wort and run cold water through it, which pulls the heat out of the wort.
2. Counterflow Wort Chiller
Counterflow wort chillers have two sets of tubing, one inside the other. Wort runs through the inside copper tubing and cold water runs through the outside tubing in the opposite direction. This means that the wort it always running past ever-colder water as it passes through the chiller.
These chillers are more difficult to clean than immersion chillers but they are more efficient, so you can cool a larger batch of beer with them in a reasonable amount of time.
3. Plate Wort Chiller
Plate chillers Are probably the most efficient style of chiller. They function like a counterflow chiller, but instead of tubing the chiller is composed of a box with a bunch of little plates inside. Cold water passes by one side of each plate and hot wort passes by the other side. These are the most compact wort chillers and they are every efficient but they are the most difficult to clean.
Do some research about wort chillers. If in doubt, stop by your local home brewing supply store and they will be able to help you find the chiller that is right for you.