IPA recipe tweak and efficiency drop
 

Several months ago I brewed a 5.5G batch of Bell's Two Hearted Clone courtesy of eschatz. Recipe here: http://www.homebrewtalk.com/f69/bells-two-hearted-ale-clone-close-they-come-91488/.
Everything went pretty well and I got a bewhouse efficiency of 67%. Since then I have really dialed in my system and this weekend brewed the same recipe save some slight changes in the grain bill. The grain bill was a bit different due to what my LHBS had in stock.
Heres the new recipe vs the old:
10# 2-row
3# CarraVienne (vs 2.5# Vienna Malt in old)
.5# Cara-Pils/Dextrine
.5# Crystal 30L (vs .5# Crystal 20L in old)

This brew day went perfectly. Hit all the temps, times etc. I was really excited about this one. I took my gravity readings, however, and my efficiency dropped to 59% :mad:. Now there is one major difference between the two batches (aside from slightly different grain bill): The grain was milled at 2 different brew stores. If anything though, this most recent grain looked finer.

So, heres the bottom line. Do you think that switch from Vienna to Carravienne or the change from C20L to C30L would cause my efficiency drop? Or is it most likely the two different mills? TIA :mug:

Caravienna is a crystal malt, and not a basemalt like Vienna malt.

To leave out 2.5 pounds of base malt and replace it with 3# crystal malt means too much crystal malt (it looks like your recipe is nearly 30% crystal malt, and it should be about 4%!) and not enough base malt. You'll have a sweet beer, and it may not attenuate that well, and that is also the reason for the lower OG.

With the amount of crystal malt does this mean there should have been a mash rest? Just trying to learn the differences.

No. Crystal malt is "premashed" so to speak, and has crystalline sugars available whether mashed or steeped. It doesn't really provide much in the way of fermentables but it gives color and flavor. It's great in limited quantities, and the quantities depend on the recipe. For most IPAs, I use 0-5% crystal malt, and for something like American ambers I've gone up to 15% with success.

Wow. I swapped out Vienna for CarrVienne b/c I thought it would be the closest substitute. After reading up on different grains I now realize that ~30% of my grain bill was unfermentable crystal malt. What does this mean for my beer? Is it just going to be super sweet? Also, as enlightening as is the is it still doesn't explain my drop in efficiency...

It'll have a lot of residual sugars, so yes, it'll be a bit sweeter and should finish slighter higher than expected.

As for efficiency, you can't compare the two, as you didn't has as much fermentable as the previous recipe. However, past that.. You could explain your process... Something changed, or you didn't get a handle on volumes correctly...a number of things could have changed, besides the grain bill.

There is some truth to this. I double batch sparge and my 1st runnings were short by about a 1/2 a gallon. I increased my sparge volume to compensate and hit my pre-boil volume pretty much on the money. This raises the question, do different grains effect grain absorption?

Also as to the attenuation. One would assume that since crystal malts were about 30% of my grain bill, my estimated FG would be fairly high. However, on Beersmith the estimated FG is 1.013, same as for the 1st two hearted recipe. Why is estimated FG not higher if there are more unfermentable sugars present in the wort?

Beersmith has some flaws, and that is one of them. I always ignore the predicted FG in Beersmith. As an example, in version 1.4, you could have 100% honey as your fermentable and Beersmith would give you the same predicted FG as if you used 100% crystal malt mashed at 158! Of course, that is not ever going to happen. When guestimating the FG, Beersmith fails usually because it just isn't smart enough to consider the amount of fermentables, the probable attenuation % of the yeast, and the mash temperature. It just gives you a predictable 75% attenuation. I have tried it with the new version of Beersmith, which may have been improved to at least consider the yeast strain when giving you the predicted FG. But it's still pretty useless.

Hmm good to know. Seems like a pretty big flaw and something that would be fairly easy to fix. Do you know of another program/online calculator that gives a better estimation as to FG?

No. I think all of the ones I've used or heard of have the same issues.