FG 1.005 - WTF

[JammyBStard]

What Has happened here?

My First English IPA in a while has finished at 1.005 (I checked with three Hydrometers)

Primary:
Mashed at 67'c
Fermented 1 week 19'c,
Pale Malt, Maris Otter (3.0 SRM) Grain 66.59 %
Munich Malt (9.0 SRM) Grain 9.51 %
Wheat, Torrified (1.7 SRM) Grain 7.13 %
Barley, Flaked (1.7 SRM) Grain 2.38 %
Black (Patent) Malt (500.0 SRM) Grain 1.90 %
Irish Moss (Boil 1.0 min) Misc

Secondry:
Fermented
1 week 19'C ramped up-to 21'c
Cane (Beet) Sugar (0.0 SRM) Sugar 12.49 %

SafAle US05

SG 1.050
FG 1.005

The result seems very good not too dry at all, sweet if anything but generally very good.
But what accounts for the very low fg? I suppose it's got to be somthing to do with the sugar or a wild yeast (it was dry hopped with 25g of cones)
I think the thing that bothers me about it is it's a good beer, but probably not repeatable because of the impossible finishing gravity.

any ideas?

[micromaniac]

ive had 3 brews on the trot go lower than that but that was when i was exprenting with overnight mashing. did you do an extended mash? by the way i was,nt keen on the rusults

[JammyBStard]

Not extended, It had a rest at 50 and then it stuck and I had to dig it out, fix the tun and mess around getting it back up to temp, so it wasn't a standard mash. However it was a split batch with two different yeasts and the other one (no secondry sugar) finished at 1014 so I assume it was post mash!

[darkonnis]

I quite like US05, it finishes quite well and while that seems a bit low I wouldn't worry. Could try it again? I can't see why it would have gone that low as even a reduced mash temp as a result of digging it out would have give nsimilar results with the other yeast... speaking of which what yeast did you use?

[Rookie]

My last batch was a pale ale that S-05 took from 1.044 to 1.007.
This quality makes S-05 good for fairly high gravity beers.

[CestrIan]

Could be an infection, lactic or acetic or could be wild yeast, they just don't know when to stop!!

[Brewmeister]

What temp was it when you took your reading? If I was a betting man I would put my money on wild yeast.

[zgoda]

Are you confident with your thermometer and mash tun insulation? I'd suspect the mash temp was too low if there's no signs of wild yeast contamination.

[JammyBStard]

I quite like US05, it finishes quite well and while that seems a bit low I wouldn't worry. Could try it again? I can't see why it would have gone that low as even a reduced mash temp as a result of digging it out would have give nsimilar results with the other yeast... speaking of which what yeast did you use?

The other yeast used was S-04, that finished at 1.014

What temp was it when you took your reading? If I was a betting man I would put my money on wild yeast.

1.005 was temperature adjusted (calibrated at 20'c)

Are you confident with your thermometer and mash tun insulation? I'd suspect the mash temp was too low if there's no signs of wild yeast contamination.

I think even if I'd mashed at 65' i wouldnt expect below 1.008

[zgoda]

What about 63? I had once such beer, fermented down to 1.006, mashed 50 mins at 63. Faulty thermometer was lying it's 66.

[JammyBStard]

What about 63? I had once such beer, fermented down to 1.006, mashed 50 mins at 63. Faulty thermometer was lying it's 66.

I guess I'll check my thermometers but I dont use cheap digital thermos because there always out by a degree or two. I use two or three Youngs glass brewing thermometers and check they give to a degree or so the same reading.

I'm not sure how to do the maths on this but perhaps it has somthing to do with the way I did my secondry.

First I made about 16L of 1052 wert with just the grain. Fermented with US-05 for one week. lets say this could have gone down to 1010.

Then I moved it to secondry ontop of 3L of sugar-wash with a starting gravity of 1064

As the sugar was very fermentable it could have gon down to 1.000 I think. Did I then effectivly waterdown the beer giving the low FG???