[Iliff Ave]

Let's assume or pretend that I don't have a fermentation issue. Is there any reason to expect such a large difference in attenuation for the two beers below?

Beer 1:
85% pilsner
15% vienna
Mash at 152F for 60 minutes
1.053 > 1.011
W34/70 - under-pitched - 80% attenuation

Beer 2:
100% red x
mash at 152F for 60 minutes
1.051 > 1.016
W34/70 from beer 1 (calculated using mr malty) - 67.5% attenuation

[Wort-H.O.G.]

if your wondering if the malt is the reason-I'd say its not likely. redx didnt cause any issues when ive used.

but as you probably suspect- yeast pitched (health, qty) and fermentation would be where I would look.

[Iliff Ave]

if your wondering if the malt is the reason-I'd say its not likely. redx didnt cause any issues when ive used.

but as you probably suspect- yeast pitched (health, qty) and fermentation would be where I would look.

Right. I just thought it was curious that the underpitched beer would attenuate more than the beer that used 1 week old slurry. That must have nothing to do with it.

Could it have something to do with the fact that I repitched the slurry from the underpitched beer? I find it funny that I get better results from doing things incorrectly (underpitching). I guess there are a lot of other factors at play here. Maybe the wort was not oxyegenated well or something else...

[Wort-H.O.G.]

right, could be any of the variables you mentioned...

[kramerog]

Malt X has a lot less enzymes than pilsener and Vienna so the wort is more dextrinous.  From what I can glean from the internet, it has barely enough enyzmes to convert so about 1/3 of that of pilsenser and Vienna. 

[brewinhard]

Malt X has a lot less enzymes than pilsener and Vienna so the wort is more dextrinous.  From what I can glean from the internet, it has barely enough enyzmes to convert so about 1/3 of that of pilsenser and Vienna.

Interesting.  So maybe lack of full conversion at 152F?

[Wort-H.O.G.]

I had no issue with all redx attenuating. mashed 150F and went from 1.055 to 1.010 with wlp090.

[klickitat jim]

Ive made multiple 100% Red X beers and have not had this problem.

[The Beerery]

You didn't get full conversion. Is it safe to assume you didn't perform a iodine test?

[denny]

You didn't get full conversion. Is it safe to assume you didn't perform a iodine test?

How can you conclude that he didn't get full conversion  Why couldn't it be something else?

[Iliff Ave]

Thanks all. Sounds like I either didn't get full conversion which I had not considered or had a fermentation problem.

The sample tasted good so I am ok with it. I added 4 oz of sugar, roused the yeast, and raised the temp a bit in attempt get squeeze out a couple more points...

[kramerog]

Thanks all. Sounds like I either didn't get full conversion which I had not considered or had a fermentation problem.

The sample tasted good so I am ok with it. I added 4 oz of sugar, roused the yeast, and raised the temp a bit in attempt get squeeze out a couple more points...

You can have full starch conversion, but still have a dextrinous wort.  You can do a fast ferment test to determine if you have a yeast or mash issue.

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[Iliff Ave]

I have not taken a final reading however something occurred to me...

A similar situation occurred recently when repitching K97 slurry into a brown ale. The attenuation was much lower than expected and others here suggested it is likely due depleted oxygen reserves from the dry yeast and that I did not aerate well enough. At least that is what I took from it. Is this possibly the case here? If so, it seems that my aeration method works well in direct pitching scenarios but not when repitching slurry.

[kramerog]

Could be insufficient aeration over 2 pitches that is the problem.

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[Iliff Ave]

There seems to be something wrong with my process (aeration) when repitching dry yeast slurry. I don't do it very often but I seem to have more issues when I do. For me, the savings in money doesn't appear to be worth the headache.