Stouts

Would failing to add lactose to a sweet stout mess with my FG?

I input a recipe into brewer's friend and came up with a target OG of 1.055 (I hit 1.053) and a target FG of 1.015. Took my FG reading today after 18 days of fermentation and I'm at 1.021. I forgot to add the Lactose to this recipe, so basically the stout I'm making won't be sweet. I'm curious though if this is going to mess with my FG? I'm obviously not getting good attenuation here and I'm wondering why. Thanks!

My understanding is that lactose s an unfermentable sugar, so it would not contribute to your FG. But if you think about it, it would make the wort more dense, there froe seeming to "add" gravity points that will not go away.
BUT, an FG of 1.021 does seem quite high given the starting gravity. Did your yeast stall?

1. If you havent bottled or kegged yet, you can boil the lactose in either a bit of the wort or some water, and add that to the batch. its not too late!

2. you may want to try to rouse the yeast before bottling to avoid over carbonation. if kegging, you're going to be fine (albeit a bit sweet).

3. Lactose WILL affect your final gravity, but in the opposite way you're saying. Adding it will RAISE the FG, as the sugars increase the density of the wort, which is what the hydrometer is reading (liquid density). 1.015 sounds like its the gravity, not including the lactose... but i could be wrong. it could be really dry, with lactose added back in.

so, what yeast did you use? starter? mash temp?

I brewed this on 5/20/12. It's a 1-gallon all grain batch. Here are the stats:

Malts and Fermentables
Pale 2-Row- 1.50 lb
Caramel/Crystal Malt 60L- 0.30 lb
Roasted Barley- 0.20 lb
Pale Chocolate- 0.15 lb

Hops
Chinook- 0.09 oz @ 60 min. (11.8 AA's. Recipe calls for 24 IBU's).

Misc.
1/5 Whirlfloc tablet @ 15 min.

Yeast
US-04- Per MrMalty, pitch: 0.2 packets (rounded to .5)

(Based on 70% efficiency)
Target OG: 1.055
My OG: 68* @ 1.052 = 1.053 (68% efficiency)
Target FG: 1.015
My FG:

Strike temp 158
Mash temp 154
Covered and put in pre-warmed oven for 60 min.
After 60 min, took out and took temp. Temp was around 154/153
Heated wort to 170 and cut the heat, covering and let sit for 10 min.
Removed bag after 10 min and squeezed out all remaining wort and brought to boil

Added hops/etc as per above

After 60 min., cooled down to 70 degrees, strained, and took OG reading (see above)

Pitched yeast at 4:30 PM

Added a few drops of Fermcap S.

Put into fermentation chamber. Ferment at 66 degrees for 21 days.

Temps were 66 degrees for the first 9 days. Then after initial (vigorous fermentation) was over, I dropped the temp in my fermentation chamber to accommodate a Dogfish Head 60 Min IPA. So after the first 9 days at 66, the temp of the stout went to 60 on day 10, 64 on day 11, 62 on day 12, 13, and 14. Then I took it out of the fermentation chamber to accommodate another beer and put it in my walk in closet were the temp went to 70 for day 15, 16, and 17, which is where I'm at now.

I'd say give it a good shake. get the yeast in suspension, and leave it warm for another few days. if that doesnt work, pitch the rest of the packet of S04. that stuffs a beast, but if i remember right, its hard to wake back up after it falls asleep.

if that doesnt work, its probably as fermented as its going to get.