Over Pitching Yeast

I think I have become very accustomed to pitching more yeast than Mr Malty reccomends, ALOT more, like double. For example, I am brewing 10 gallongs of Kolsch this weekend. Mr Malty says 1.91 litres of starter required. I am going to go with an entire gallon (4 liters).

Since I have started pitching yeast at very high rates my beers ferment out clean and very quick. I haven't found any issues with it, but I am wondering what folks opinions are on the topic.

The most important aspect of yeast pitching is viability. You're sending an army into battle. Would you rather send 100 Army Rangers or 1000 little old ladies?

Professional breweries, with access to labs and yeast propagation systems, know that their yeast is fresh and healthy. The MrMalty calculator guesses viability based on the age of the smack pack. MrMalty doesn't know how well the yeast was treated before you got it, so there's not way your viability percentage is accurate. It's probably an OK guess most of the time, but it's possible to pitch exactly what MrMalty recommends, but be effectively under-pitching because of poor viability.

So I'd say it's better to think you're over-pitching and have your beer ferment quickly than to underpitch, stress your yeast, and open the door to infection.

The only time I think it would be a problem is when brewing styles where you want some yeast character. For example, I intentionally underpitch (slightly) weizens to make them work a little harder and increase the phenol/ester production. For clean styles like Kolsch you'll probably have a great beer.

I am almost exclusively make starters from washed samples, so viability I do now know. This is another "grey area", but judging by color and knowing the age of the sample you can usually get an idea. I like to "coddle" older yeast samples and bring them up a little slower to get a nice big, healthy starter going.

2 liters is pretty much my default starter size for a 6 gallon batch under 1.060 or so, anything bigger and I go with a full gallon or more.

I seriously question the conventional wisdom that underpitching means more/better yeast character.

Most of the published pitching rates are based on industrial scale breweries. Large conicals retard ester formation, and they are usually pressurized a bit, to further retard ester production. A pail or a carboy will naturally allow way more yeast character to come through. I always pitch at a high rate and I get plenty of yeast character on all my Belgian styles.

Those numbers are only a guideline. There is no exact science dictating how many cells/*P/mL to use. There are guidelines, but every brewer has to work out for him/herself what is appropriate given the fermentation conditions.

Short Answer: I usually overpitch slightly, just because I feel like it.