Utilization of Harvested Yeast

I'll start off by saying that I've read the stickies on yeast washing and slanting--I've been washing/harvesting for a couple of years now and intend to start slanting, but this question relates specifically to harvested yeast.

I've been fairly unscrupulous in the past and have ended up with some rather interesting brews as a result, which I can best attribute to harvested yeast of later (or, horrors!) contaminated generations. Obviously, fixing contamination issues is easy, and is merely a matter of altering packaging procedures. I'm not horribly worried about THAT, as I've only ever contaminated one batch and that had nothing to do with yeast.

So, my question. For those who harvest yeast, are you concerned about things like generations, gravities, and the like? IE, if I harvest yeast from a 1.060 batch, I've read things in regards to only pitching that yeast into a batch of higher gravity. Additionally, have read that one should only harvest for about 2 to 3 generations. Of course, use of a starter should be assumed, and size/length of starter related to OG....

Thoughts? Basically looking for general guidelines for utilization of harvested yeast. Thanks!

Well, you can get so much yeast out of a single batch of beer that you would have to be brewing an incredible amount to take your yeast out very many generations unless that's what you want to do. I'm starting to re-use a strain as many generations as I can manage to see if I can mutate it into something of a house yeast.

As for gravity for re-use, I don't put much stock into the whole not harvesting from high gravity batches. Yeast are hardy buggers- a 1.070 beer is no problem for them if you're treating them right (pitching rates and oxygen, fermentation temps). My fermentations are typically completely finished in less than a week, even at higher gravities, so I have no problem harvesting yeast from fresh batches that way.

Thanks for the thoughts. That's the type of info I'm looking for. I've done, as stated, a few generations at a time, but I'm in a more permanent space now and intend to be a little more calculated about my washing and harvesting.

How are you developing your house strain? I would think that if you're relying on mutation, you'll eventually mutate it out of existence (or, have an impermanent or unreliable house strain at best)...unless you plan on generating a large starter every once in a while and then hiding it away?

Are you attempting to cross yeasts? Or just waiting to see what happens when it starts to mutate?

I'll just take it out as many generations as I can manage. The changes are so subtle even after years of reuse, that unless something really goes weird, I suspect it won't be very noticeable.

I suppose if it gets to a place that's really awesome and unique, I would make a huge starter and slant it out and keep it around in glycerol stocks for all time, but right now it's more of an experiment than anything.