re-using hefeweizen yeast

So let's say (purely hypothetically of course... ) that I want to brew more hefeweizen and I have a recently bottled batch, but don't want to spend the money for another smack pack of weihenstephan ninja-yeast... How to Brew says you need a "1 or 1.5 quart starter for a moderate gravity beer." Well, I figure a fresh hefeweizen is a decent starter, right? And a quart is what, about 3 12 oz bottles? Any reason why just dumping a few bottles in my new wort shouldn't work? I'll (again purely hypothetically...) have 3 gallons of ~1.050 wort.

It might work really really slowly. I don't think the math works out quite like you are hopping though. The small amount of yeast in even 3 bottles is far from the amount of yeast in a 1 qt starter, plus they are inactive and would take quite some time to get working on your wort. If you took those bottles and were able to propagate the yeast for a couple of weeks then it would work.

Probably easier to just buy some more though and then harvest the yeast after fermentation for future use. Ooo that reminds me I have to go do that now.

Next time just save the yeast from the primary and use it for the next beer. Swirl it around and pour it into a flask of covered container and keep it in the fridge for up to a week.

Search "yeast washing" and read up on it...I wash my yeast all the time.

I only buy a few vials every year, but manage to have AT LEAST 40 vials of yeast on-hand...

Well OK, I lied when I said it was a purely hypothetical situation... I haven't bottled yet

The yeast will need to last about three weeks so it looks like I'll be harvesting form primary and washing. For reference, if I am planning on a 1 qt starter, how long should I plan on having to culture that for from a jar of washed yeast-- should I start three days in advance of brewing? A week?

I pull at least a quart from each fermenter once I rack to keg, no reason you can't pull more or even pitch on the same yeast cake. You might want to get some yeast nutrients as hefe yeast tends to wear itself out and does not store well for long periods without a little wake up. Just harvesting a quart will work, it might just take a day or two to get going.

well, I have never harvested or cultured yeast before and I read the yeast washing sticky but since I ferment in a plastic pail I can't see all those pretty layers he talks about, and we were bottling late last night so I decided f it and threw the yeast away. I'll buy another pack when the time comes, and maybe by then I'll have done enough reading that I feel more confident saving some. I am thinking of following the method Papazian's method from TCJHB, it involves no washing and looks very straightforward, using equipment I have lying around.

Two questions:

1) What is the advantage to washing as opposed to just saving a bunch of yeast cake like Papazian shows?

2) Any tips for washing yeast coming from a plastic pail?

I don't wash, I just stir it up and pull a couple quarts of slurry out. Never had any problems so far.

How many times will you re-use yeast?

Those with questions should re-read BernieBrewer's yeast washing thread. It's really not as difficult as you think. I got some used canning jars from a garage sale and accomplished this with minimal cash/time outlay. I've only done it with one yeast(wlp300) and just fermented with the third jar of it, this one with 6+ months in the fridge. It's slowed down coming back to life(as my "would you use this starter" thread proves), but after making a starter and shaking the f$#% out of the carboy it took off faster than any of the other jars. Just take it for what it is, a money saver. I have a lab rat SWMBO in the house as well, and when I tell her what I'm doing she raises an eyebrow, but doesn't balk at the procedure. The proof is in the product. RDWHAHB

I just discarded some Irish ale yeast that had been used about 8 times, just pitching on the same cake. I had intended to use it again but the empty carboys were in the garage when I milled my last batch, causing the little bit of wort in the empty carboys to get infected with something.

The best part about re-using your yeast, is that you have a bunch of mason jars in the fridge, making your wife say, "When are you going to get rid of those jars!!??"

To which you reply. "Well, I guess I better start another batch of beer!"