FG Mystery with Vanilla porter. Help

I have an odd question with my Vanilla Porter. Backstory:

Made a partial Mash kit from NB. OG was 1.058. Used dry Safale s05. Primaried for three weeks and racked last weekend into a glass Carboy with vanilla beans cut up. Gravity reading was 1.021. Tasted funny, sort of metalic and I had a slight concern about infection Was also a little concerned about stuck fermentation with the high gravity so did something I have never done and threw an extra packet of S-04 in that I had laying around. Also added a little lactose - like 6-8 ounces.

I just racked to my bottling bucket and took a reading with two different hydometers and it reads 1.025. Gravity actually went up! temps have been a steady 72f in my basement. Beer does seem to have a little residual carbonation from the Carboy, could that raise the gravity? Thoughts? Tastes great now but I'm afraid of bottle bombs.

I've made about 25 batches to date and have never had an issue.

FYI there is a small yeast cake in my secondary so more fermentation seems to have occurred - unless it has just settled out.

My Porters with S-04 have always finished 1.018-1.020 and I like them right here, so I see no prop. with .021 for a Porter. Your gravity went up because you added lactose, an unfermentable sugar. The S-04 addition was wasted.

strambo said:

My Porters with S-04 have always finished 1.018-1.020 and I like them right here, so I see no prop. with .021 for a Porter. Your gravity went up because you added lactose, an unfermentable sugar. The S-04 addition was wasted.

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Thanks. Ive never had anything finish that high, including several stouts and porters, thus the concern - and the original yeast was S-05. I decided not to bottle today, and several ounces of oak chips sitting in rum, which I will add and let sit for a couple more weeks. Should be a good holiday brew.

Thats the only thing I didn't like about their kits. They did not give what the expected fg was suppose to be.

Gravity went up because you added unfermentable sugar (lactose).

1.021 does seem high to me, but not totally out of range. You should have warmed it up to see if you could get any more from it.

The S-04 was wasted.

I partial mash also...and yes, US-05 should have taken it down a little more...but 1.021 is not a stalled ferment, just a finishing a hair high. I bet it will be really good with the lactose, slightly sweet and the rum oak chips will be nice if not overdone. I'm about to brew my holiday beer, a RIS with cinnamon/vanilla based on ramping up my partial mash Porter recipe. I'll be switching from S-04 to US-05 since the '05 can handle the higher ABV.

beerman0001 said:

Thats the only thing I didn't like about their kits. They did not give what the expected fg was suppose to be.

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If you divide your Last two OG digits by 4 you will get the estimated FG