stout fermentation not finshing

[techrunner]

well i attempted a deception cream stout about 3 weeks ago, but i had a few odd issues. my ingredients were a little old, probably sat in the fridge and the hops in the freezer for 6 months or so. just got busy. the starter sat in the fridge sealed up for a long cold crash for about 2 months.

when i took an OG, it was 1.072, about 0.010 higher than i see anyone else posting in the recipe thread. its now at 1.030, and has been for a week and a half at least.

fermentation was extremely active, i had nothing for about a day, then blowoff for another day and a half or so, then it died down. i warmed it up to 70-72, and swirled it 2-3 times a day for about the last week, trying to get it to finish up.

i guess i should say that the starter was white labs irish ale, washed from another batch. i tossed in a packet of muntons dry yeast too, afraid that the starter might be dead after i let it sit so long. the samples actually taste pretty good, despite my efforts to destroy it.

i'm just curious why it seems to have an extra 0.010 in there that won't ferment. would that be from a little too much lactose? i just assumed that measurements from the supplier were on, but maybe they got a little extra in there accidently. any thoughts? thanks guys,

 

[david_42]

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[carrotmalt]

I think .5 lbs of lactose adds around .7 points. If you deduct that from your starting and ending gravities, you end up with 65% attenuation.

White Labs lists WLP004 Attenuation: 69-74% - I'd say close enough considering old/sleepy yeast etc. I've seen several threads on stouts not attenuating well due to lots of unfermentables and lactose.

 

[TheWeeb]

I have to piggy-back on this, similar issue. I did a kludge of two different recipes, ending up with the following:
6 lbs dark LME
1 lb 60L
1 lb Chocolate malt
1 lb flaked oats
.5 lb roasted barley
.75 lbs lactose

My OG was 1.064, three weeks later, steady at 1.024 for the past few days. When I use the Hopville beer calculator, my OG is dead on, but FG should be 1.014. Adding or removing the lactose in the calculator makes no difference in FG, which is odd.

Carrotmalt, do you mean .007?

The sample I just took tastes pretty awesome, but I do have a packet of Coopers yeast just dying to be added to bring it down a few points, if possible.

 

[manoaction]

Lactose is used because it isn't supposed to ferment. It adds sweetness to a beer when other forms of sugar are converted to alcohol. If you've added lactose to your beer, expect to have higher gravity FGs, that's the whole point of adding it.

 

[TheWeeb]

Allow me to rephrase my post, as I know the purpose of lactose, and at times my writing is not clear.

What is the best way of calculating the contribution non-fermentables (lactose) make to the specific gravity?

I think this would be helpful in understanding whether a brew is finished or stuck.

 

[carrotmalt]

Carrotmalt, do you mean .007?

Well, I just tried to find a definitive answer as to the potential of lactose and the answers I found were all over the place. Looks like a pound in a gallon should yield around 1.040 - 1.045.

If you take the lesser of the two, divide it by 5 (for 5 gal batch), you'd have roughly a .008 increase in OG and the same for FG. This recipe used half a pound, so I guess it might be closer to .004 rather than the .007 I mentioned earlier.

If someone can come up with a firm answer (link please) on what the potential gravity for lactose is let use know.