Hydrometer reading 13 hours after pitching yeast

I currently have my first brew in my primary fermenter, an Irish Stout Ale recipe from midwest.

6lb Dark LME Malt extract, 1 tsp. Gypsum
4 oz. chocolate malt, 4 oz. caramel 10L, 4 oz. roasted barley, 4 oz. flaked barley
1/2 oz. 12.5% AAU Nuget hops boil 60 min, 1 oz. 6% AAU Glacier hops boil 2 min
Dry Yeast

Last night, after racking the wort, I took a hydrometer reading without first mixing the wort and H2O. I had vigorously aerated the H2O so that's not causing a problem with fermentation... the bubbling this morning is a testament to that.

My problem is that my hydrometer reading before I pitched the yeast read 1.038 @ 72F. I realized for an Irish Stout this is rather low, and began researching. I found a similar situation on this forum that was caused by not thoroughly mixing the wort. Since the wort is denser than water, it sinks, throwing off the reading with the hydrometer at the top.. similar to the 'rivers' of salt water at the bottom of the ocean.

So I sterilized my hydrometer and spoon, uncapped my fermenter, and slowly swirled for a few seconds, and took another reading. This time it came out to be 1.076 @ 81F, 13 hours after pitching the yeast.

I'm curious to know how this will affect the accuracy of determining alcohol % when I take my FG. I realize everything is fine, save for me opening up the lid after merely 13 hours, risking contamination. But I would like advise from those more knowledgeable than I of this.

Cheers
-Kyle

I would just go with that reading as a starting gravity.

You'll know how much alcohol is in it when you can't stand up after having a few.

Based on your recipe I would think that the first gravity you measured is closer to actual. What was the final volume in your fermenter?

Alcohol Content = some

BeerSmith calculates your recipe at 1.047. Assuming you have exactly 5 gallons of wort, the OG is 1.047 +/- 0.002. Either you're reading the hydrometer incorrectly, you have particles getting in its way, your hydrometer is broken, or your wort is not stirred well. My money is on the latter, but don't try to "fix" it. Fermentation action will finish the work for you. Just use 1.047 as the OG for this batch.

An inaccurate OG will result in an inaccurate ABV calculation. The formula is this:

ABV = (OG - FG) * 131

Additionally, taking a specific gravity reading shortly after fermentation has begun is nearly worthless. You know the SG is nowhere near terminal, and it's definitely less than OG. So, your second sample was a waste of time and beer (sorry that was a bit blunt...).

Also, avoid adding mineral/salt content (i.e., gypsum) to further extract batches. Unless you know your water chemistry as well as the extract's mineral content, and you've calculated the appropriate mineral addition to help your beer, you're probably not helping your beer. Extract + any water should contain abundant mineral content for the yeast and flavor of your beer.

Liquidicem said:

Based on your recipe I would think that the first gravity you measured is closer to actual. What was the final volume in your fermenter?

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~5.2 Gal total

Creobane said:

~5.2 Gal total

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Then use 1.045 as the OG (to account for the volume increase).