yeast banking- slanting vs glycerine freezing vs?

so i've been reading up on the various ways of yeast banking, and am wondering what the more common techniques are? Seems there's two main camps, slanting on agar and freezing with glycerine. Both seem to have equal utility at 6-12 months, but it seems that glycerine freezing can result in easier long term (1 year+) storage? pros/cons to either? what are your thoughts, fellow homebrewers?

I've done both, and as you said they do equally well at 6-12mo, but longer than that, you'll want to freeze in glycerin. I just thawed my whole stock of yeast over 3 years old just to check viability, and they're all good, very active and give the same flavor profile as they did when I froze them. Very hardy creatures, but keeping them at 4C too long stresses them out, and you're asking for mutations over a year at that temp.

wanted to tack on an additional question- any thoughts on using vials with liquid yeast/slurry and storing at fridge/keezer temps? let's say 38-40 degrees w/out glycerine? assume these would have to be used after, ~3 months or so similar to white labs/wyeast store bought vials/packs? for a "house strain" this seems to make more sense that freezing just fora month or two

I've been doing quite a bit of research on this subject, an am in the middle of a year long experiment to quantify effects of storage methods. Freezing will reduce viability to about 50%, but it drops very little after that. Viability in the fridge will reach 50% in a few months. Contamination is more of an issue in the fridge that the freezer because of the temperature difference, and if the container is not perfectly sealed the liquid will support growth. In the freezer the yeast is protected in a block of ice.

So generally, storage for a few months the fridge is good. For longer storage freeze.

Thedutchtouch said:

wanted to tack on an additional question- any thoughts on using vials with liquid yeast/slurry and storing at fridge/keezer temps? let's say 38-40 degrees w/out glycerine? assume these would have to be used after, ~3 months or so similar to white labs/wyeast store bought vials/packs? for a "house strain" this seems to make more sense that freezing just fora month or two

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I would store the yeast under beer, not washed (personal preference), fermented fully from a low gravity starter that was "sterilized" with a pressure cooker, including the vials (don't cook White Labs vials) and any glassware you might use collecting/growing the yeast. Basically I am restating the above post, to store in the fridge you have to be as sure as possible there is no contamination present, which is why I wouldn't use slurry from a primary bucket. I've stored yeast like this in vials no problem for at least a year that get going immediately in a starter, MrMalty viability calculator be damned. Not that I would suggest going that long though.

As an aside, I'm sure you didn't mean it, but don't store the cells in glycerine in the fridge.

From what I know, if you don't use glycerin when freezing yeast the ice will damage the cell walls and kill most if not all the yeast.

I do 25% yeast 25% glycerin and 50% water and have used yeast frozen for well over a year. Getting close to 2 years. I have some stored now for more than 2 years. I will need to see how this goes. I will be resurrecting some as soon as all this snow melts and I can get back out on my porch. I need at least 40 degrees for my comfort, until then it is BIAB in the kitchen. I have been using dry yeast recently.