How much yeast for a 1-gallon batch?

Recently I've been experimenting with recipes by brewing 1-gallon batches (about a gallon and and half post boil). I was using dry yeast, about half a pack, in the primary. I'm thinking of moving over to WYeast smack packs.

Should I scale down the amount of yeast I use? Know they're designed for a 5-gallon batch, so wasn't sure as this is my first time using liquid yeast for the 1-gallon batch. Thanks!

If you want to conserve yeast, you can use significantly less than a whole pack... I think something like 1/5 of 1/4 pack is enough. But if that's not a concern, pitching the whole pack should be fine too. That is "overpitching," but from what I've heard it's not enough to cause off flavors.

Edit: Oh wait, I misread your post and thought you were still asking about dry. Well, same logic still generally applies, though you may want to consider checking with MrMalty's: http://www.mrmalty.com/calc/calc.html

I'd make a small starter and divide it into 5 equal portions - that way you can save what you don't need right away under pre-boiled water in a mason jar.

@ jsweet - thanks for that calc! That's going to be super handy for all my batches going forward. jackpot

@ ArcneXor - what do mean by under pre-boiled water? Also, how long can I keep a starter? Can it stay out or does it need to go in the fridge? On a side note, see that you have a Peanut Butter Porter on tap. How'd it turn out? I have one in the secondary right now.

Kevin,

the water is pre-boiled so that it is near-sterile and there is no oxygen in it, which helps the yeast live longer. You can keep a starter out for a few days without problems, but it's better to store starters, slurries and washed yeast in the fridge to reduce cell die-off. That way, they can last weeks to months.

The Peanut Butter Porter didn't turn out as peanuty as I had hoped due to a stupid mistake that I hadn't foreseen (namely that the PB2 got trapped by the kettle screen and thus didn't make it into the fermentor), but it's still very good. Next time I'll just add the powder to the primary.

I tend to use about 2 tbsp out of a smack pack for 1 gallon batches. You can use the whole thing, but it takes up a lot of room if you're using a 1 gallon carboy.

Thanks all!

@ ArcneXor - sorry the PBP didn't come out like you hoped. Hope round 2 comes out better

I would second the dividing it into equal starters idea. I might be a little concerned keeping the yeast sterile after opening the pack. But I guess if you put it into a sanitized jar or something immediately that might work too.

Sorry to re open this post 4 yrs later... but I've just started to get into doing 1 gal batches myself - and I'm starting to think yeast washing might be the best idea for me to save on $$$ . When you put it into a mason jar (sorry if this is going to sound dumb) does it matter on the size of the mason far? for instance can I get away with using a 4oz jar while splitting up my yeast ?