Imperial Stout with the Grainfather - Questions

[fragglerock]

About a month ago I purchased my Grainfather (110v) and absolutely love it. The Brown Ale and Saison that I brewed with it are coming along nicely. However, Friday I thought I would give an Imperial Stout a shot and had an issue that stumps even my LHBS. Since the Grainfather couldn't handle the full 5 gallon grain bill I scaled it down to 4 gallons for a total grain weight of 16.7 lbs. I used the calculator on the Grainfather website, mashed with 6.33 gallons for 60 minutes at 152 F and sparged with .59 gallons at 168. After the sparge was finished my pre-boil volume as 7 gallons! I had lost none to grain absorption and ended up missing my target OG of 1.113 by quite a bit. I could have just boiled off as much as possible but with the slow evaporation rate, I would have been there for hours. Any ideas on what in the world happened?

 

[BrunDog]

I don't have a GF or similar single vessel... but that sparge volume doesn't seem like much, and its not possible to have no grain absorption. 17 lbs of grain should hold about 2 gallons of liquid. I suppose longer draining might reduce that a bit, but a sponge won't give up all its liquid no matter what gravity tries to do.

 

[fragglerock]

I'm some of it was actually absorbed but still, should I be getting that much volume pre-boil? I checked and re-checked (even had the wife take a look to make sure I wasn't going blind) but the level was 7 gallons. I'm still working out a lot of kinks, this is only my third all grain batch.

 

[BrunDog]

Might post this question in the GF forum or other non-electric specific forum (or have Mods move it) to get more answers.

 

[Smellyglove]

Grain absorption is not linear. My experience is that a small grist will retain more liquid than a big grist pr kg malt used. You need to adjust grain absorbtion to your grist size.

 

[azmark]

Did you mill the grain?
How much time did you take doughing in? Pour in a little, stir a lot, repeat.

 

[fragglerock]

Thanks for the responses. I'm beginning to think it was a milling issue. I milled the grain at my LHBS, tomorrow I will ask them what the settings on the mill are. I took my time doughing in, wife poured a little while I stirred.