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5gBrewer · 01-13-2007, 03:21 PM

Would dumping cold water on top of a yeast cake, before dumping the warmer wort, harm the yeast? I'm assuming that cold water wouldn't harm the yeast because liquid yeast is kept in refidgerated conditions before using.

5gB

boo boo · 01-13-2007, 03:28 PM

If you are just pouring water onto the cake then it shouldn't hurt as to temperture changes. But the question remains, why are you doing it?

5gBrewer · 01-13-2007, 03:35 PM

Well, Boo Boo...

I've got this IPA fermenting in my 6.5g carboy. When it's done, I'd like to brew up an IIPA, and rack it on top of that IPA yeast cake. When new brew, I always add 2 and 3/4 gallons of cool tap water (don't worry, it's very fine water) to the fermentor, before I add my cooled down wort, and top off with more cool water as necessary.

I've never had a problem with this method before, but then, I've never racked ontop of a yeast cake before, so I didn't know if the cool water addition would effect the yeast cake in any ill manner.

5gB

**Orfy** · 01-13-2007, 03:36 PM

Pour the water in the wort then onto the yeasy cake. Yeast don't like changes in temperature.

sonvolt · 01-13-2007, 03:38 PM

Actually, rapid temp changes will shock the yeast. If you were to dump water onto the yeast cake that happened to be the same temperature as the yeast cake, you would not have a problem. However, dumping cold water onto a yeast cake will rapidly change the temp of the yeast - shocking them. You will probably not kill all the yeast, but you will stress them by doing this.

As for reasons, I can only assume that you are an extract brewer who is attempting to cool your wort by dumping into cold water.

If I were you, I would do this - Sanitize a spoon and a mason jar. Then, being very sanitary, collect a good amount of your yeast cake into the sanitized mason jar. Clean your primary fermenter as you normally would, add your cold water, dump your wort, and ensure that you are at the proper pitching temp for the yeast strain you are using. Then, dump your harvested yeast from your sanitized mason jar.

Be careful with cleanliness.

This will get you what you need with less stress to the yeast than rapid temp changes, IMO.

**John Beere** · 01-13-2007, 03:39 PM

Quote:

Originally Posted by orfy

Pour the water in the wort then onto the yeasy cake. Yeast don't like changes in temperature.

Plus you won't accidentally add to much water if you add the wort first...

boo boo · 01-13-2007, 04:58 PM

Cool water would be within the temperture range of your finished yeast, but I agree with the guys here that you should pour your wort onto the cake first. Given the amount of yeast in a cake, the temperture difference wouldn't matter too much if the difference wasn't too much. But the pouring of warmer wort onto the just cooled yeast would stress the yeast out a bit.

Ol' Grog · 01-13-2007, 07:06 PM

The closer the temperature of the two, the better.

5gBrewer · 01-14-2007, 07:57 PM

Quote:

Originally Posted by sonvolt

If I were you, I would do this - Sanitize a spoon and a mason jar. Then, being very sanitary, collect a good amount of your yeast cake into the sanitized mason jar. Clean your primary fermenter as you normally would, add your cold water, dump your wort, and ensure that you are at the proper pitching temp for the yeast strain you are using. Then, dump your harvested yeast from your sanitized mason jar.

Be careful with cleanliness.

This will get you what you need with less stress to the yeast than rapid temp changes, IMO.

I like the sound of this idea, Sonvolt. I didn't really want to use the whole dang yeast cake anyway, as I'll be putting this all back in a 6.5g ale pale, using a small blowoff tube in the drilled lid hole. Using less yeast should make it less likely for my lid to pop!

Thanks for all your help, folks!