How does gravity change by adding D-180 Dark Candi Syrup during fermentation?

[Mogie]

I attempted to make a batch of Northern Brewer's all-grain "Big Honkin Stout". Long story short, my OG came in low at 1.055, and after 4 weeks in primary my FG was stock at 1.031. (OG target was 1.068...) I had a healthy starter of Wyeast 1332 Northwest Ale Yeast.

My Mash temp was a bit high, so I figured I had too many unfermentable sugars in there.

I ended up added 1 lb of D-180 Dark Candi Syrup, just as an experiment. I also pitched Safale US-05 yeast. Fermentation picked up again for a few days and then stopped. I took a gravity reading, and my FG was again 1.031.

So my question is, how do you calculate the change in potential alcohol and/or gravity by adding that 1 lb of D-180? D-180 is listed at 1.032 PPG.

 

[ahpsp]

Your new OG is your old OG (1.055) plus the contribution of the sugar divided by your batch size. IOW, (1.032/x gallons)+1.055.

 

[motorneuron]

1.032 PPG means that, if you added that to a gallon of water, you'd have 1.032 as the new gravity. For a five-gallon batch, straight algebra will give you 1.0064 as your gravity, or about six and a half points. So it's as if you started at 1.0614 or so instead of 1.055.

The larger question is why you keep getting stuck at 1.031, which is extremely high for a wort that started at 1.055. Unless you mashed at, say, 165F, I don't see how you could have such a high percentage of unfermentables. How high was "a bit high"? Did you oxygenate? Have you had this problem before? Have you tried rousing the yeast? What temperature were you fermenting at?

Normal advice would be to raise the temperature a bit and rouse the yeast (i.e., rock the fermenter back and forth to get it back up into the beer instead of on the bottom).

The biggest question would be whether this is a recurring problem you're having (which would suggest you need to reexamine your process), or whether this is just an odd quirk of the batch (which can happen from time to time).

 

[Mogie]

Soooo...I think I may have found my noob error.

I just bought a fancy shiny new Refractometer and used it for this batch. My mistake is that I did not know (until now) that in order to take a final gravity reading I would have to calculate and correct for alcohol. Or just use my hydrometer...oops.

So based on some Googling i did...my readings of OG 1.061 (with the 1 lb of D-180), and then my FG reading on my refractometer 1.033 (changed to Brix: OG 16.6 & FG 7.8 ) would give me a real Final gravity of 1.012 and an alcohol content of ~5.17.

But in case you're still interested, here are the answers to your questions.
I was aiming for a mash temp of 153, but somehow my calculation was off and I ended up at 155-156. I have since learned that my Thermapen is in need of calibration as its about 2 degrees off, so I was probably around 157-158.

I aerated before pitching at 70F. My yeast starter was on a stir plate for about 36 hours. And fermentation was steady at around 70. Fermentation was vigorous, and I even needed a blow off tube. When fermentation stopped and I noticed the low reading I shook the carboy up to rouse the fallen yeast but nothing happened. That's when I decided to go for broke and add the D-180 and US-05.

Anyway, tonight I'm going to take an old fashioned hydrometer reading and get ready to bottle. I have tasted it, and it does taste very roasty, with big bitter hops. I dont taste much flavor from the D-180. The beer does have a