Piotr

Recipes 

Don't even bother with 15 min; AFAIK acid rest took hours.
A friend of mine tried 2 hours, and the pH drop was really small.

Potential drawback is tannin extraction due to extedned soaking the grain in water.

menschmaschine

Recipes 

Thanks, but I'm not necessarily looking for a pH drop. My well water pH is already at 5.7. According to Horst Dornbusch, a 15 to 30 min acid rest can make a positive difference regardless of pH. I'm just testing it out to see if I notice any positive differences as I listed previously.

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Lil' Sparky

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I did two 10 gal wheat beers recently (hefeweizen and dunkelweizen). I didn't have any rice hulls so I did a beta glucan rest at ~ 105º for 15-20 mins to break up the gums to avoid a stuck mash. It seemed to work fine. I direct-fired the mash up to 153º, using a pump to recirculate during the entire protein rest, and never had any problems with the mash sticking. I got the feeling that the rest did a good job breaking up the gums like it was supposed to. Otherwise, I'm pretty sure I would've had a stuck mash at some point.

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menschmaschine

Recipes 

I brewed a Helles using an acid rest at 103°F (39.5°C) this past weekend. From my OP, the only thing I can say is that it did not have a noticeable effect on my efficiency. My efficiency came out the same as my last lager, which was a German Pils with the same grain bill and mash schedule, minus the acid rest.

When it becomes drinkable 8+ weeks from now, I'll try to remember to post back the final results, but somehow I'm not expecting much. In similarly brewed beers, I don't have chill haze issues without the acid rest and I don't filter my beer, so the only thing left is, "enhances head stability and mouthfeel of the finished beer." But my foam stability is pretty good (always room for improvement) and there's plenty of mouthfeel in my Hochkurz mash lagers.

So, I'm one step away from saying acid rests aren't worth it unless you need it for mash pH.

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samc

Recipes 

Bump - menschmaschine

OK, it's been 2+ years, what was the "final results" ?

I just did a rest on my last brew and due to some other crazy issues I couldn't determine an accurate efficiency on this batch, but curious as to what you remember of tasting the beer.

ajdelange

Recipes 

I think it would be more reasonable to call this a "beta glucan rest". For it to result in acid production you would have to hold for many hours and perhaps they did so at one time but no more.

I do a beta glucan rest more or less because that turns out to be a good temperature from which to pull a first decoction. If it busts up beta glucan bundles that's all well and good but it's not the reason I do the rest. An no, it does not nullify the need for rice hulls. The depth of the grain bed in my "lauter tun" (a 55 gal drum) is such that rice hulls are absolutely necessary - a lot of them.