Re-pitching with different yeast

[ExCathedra]

My latest batch has yet to show signs of fermentation after 36 hours. This has me wondering: if I decide to re-pitch the yeast, is it problematic to re-pitch with a different strain? Specifically, I brewed a hefeweizen and originally pitched Wyeast 3638 but would re-pitch with Wyeast 3068 due to availability. Any thoughts?

 

[whoneedsabeer]

Did you take a hydro reading, or are you simply looking for airlock activity?

What's the temp of your beer currently? Perhaps it's a bit too cold?

If I were you, I'd first look to determine why the first batch of yeast aren't doing well. Did you do a full boil or top off? Did you oxygenate the wort well enough prior to pitching?

Re-pitching a different strain won't hurt, but I have no experience with these two strains. Looking at the wyeast web site, shows these two strains having similar characteristics, so I don't think you'll have a problem with competing flavors.

Good luck!

 

[ExCathedra]

I haven't yet taken a hydro reading. But that's good advice that I'll follow as well as investigating why the yeast isn't doing well as it is. The temp is currently 70-72 (pitched at 70 with good aeration). It was a "top off" batch (2.5 gal.), how does this affect the yeast? If I re-pitch, is it safe to aerate again?

This was my first experience with a smack pack and I didn't use a starter. I smacked 2.5 hours before pitching and there wasn't significant swelling of the pack. Should I be using a starter as well? Is it uncommon for the pack not to swell?

Thanks for your advice so far.

 

[whoneedsabeer]

I asked about full boil vs. topping off because with a full boil, most of the oxygen is boiled out of solution. That makes it necessary to oxygenate. But if you topped off, you should be fine.

I've never use a smack pack myself, but from my understanding they are supposed to swell, but I'm not sure how long it's supposed to take.

A starter is probably the best way to go. That way you know your yeast are happy. You could always just rehydrate a dry yeast packet as an alternative if you don't have time to make a starter. That would be the quickest way of getting some known good yeast in your beer if you truly think you've got dead bugs.

 

[marubozo]

If you're worried and it's been a few days with a smack pack I'd pop the lid and check, and even take a sample to calm your nerves. At 70 degrees there's a good chance it fermented out overnight and you missed any airlock activity.

If you take a reading and it's still at your starting gravity, then yes, you may want to repitch. But unless you check the gravity now there's no way to be certain your yeast didn't do their job already.