Thinking about adding more sugar, your thoughts?

I have 4 gallons of a concentrate recipe that has been in the primary for 30 days and is due for secondary. Problem is, I'm getting an abv of only 10.4%, and I want to bump it up to at least 12.5%. I've been using an off brand grape juice concentrate I found at Aldies instead of welches because its cheaper. The Aldis concentrate has always produced lower abv but this is the lowest. I'm leaning towards dissolving a cup of sugar in a little bit of the wine then re-introducing it to the primary. My question is; Do I just pour it right in and hope the yeast will attack it or do I stir up the must a little? If I do stir up the must should I let it sit another month?

What was the starting gravity of this must?

What yeast did you use?

I would add the dissolved sugar to the wine and gently swirl the carboy or bucket.
If you dont get any activity, which you would measure with a Hydrometer, you may need to use a packet of yeast.

You could add sugar if you want, you could also add more concentrate instead of cane sugar, it would be a bit more flavourful than adding cane sugar. Regards, GF.

I added 2 more grape juice concentrates and gave it a gentle stir about 15 hours ago. There still isn't any airlock activity. The temp on the primary is right around 70 degrees. I'm thinking about auto siphoning to a clean primary and re pitching. What do you think?

I'd leave it alone for at least 24-48 hrs, it might take as long as 72 hrs to see any activity. As long as you thawed the concentrate before you added it, I don't see any reason to worry yet. I'd give it some time & let the yeast do it's thing. Regards, GF.

gratus fermentatio said:

I'd leave it alone for at least 24-48 hrs, it might take as long as 72 hrs to see any activity. As long as you thawed the concentrate before you added it, I don't see any reason to worry yet. I'd give it some time & let the yeast do it's thing. Regards, GF.

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It was thawed when I added it. I give it some more time. Thanks for the help, I'll get back to you a little later.

72 hrs has past and still no activity. I'm going to re pitch when I get the chance. Do you think I need to use a whole packet of yeast or just half since I only added two concentrates?