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Grape Skins and Final ABV

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Wayne Freeman

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Hi, does anyone have an estimation of how much the bag(s) of grape skins add to the final ABV?

For instance, I just bottled a batch of WE Eclipse Old Vines Zinfandel. The starting SG was 1.082 and the final was .992, which should nominally result in an ABV of 12.2%. But this kit includes two pretty large bags of grape skins, which, while you add them at the start of fermentation, don't affect the starting SG at all.

What do you think? Would the skins add the equivalent of .001? .01? .05? Is there any way to tell?
 

sour_grapes

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I will try to generate better numbers tomorrow, but I have found that the grape pack adds ~0.015 or so to the SG, or about 2% ABV.
 

Wayne Freeman

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Thanks, that gives me a better idea. Is your estimate per bag? This kit had 2 bags. There were a lot more skins than I've gotten with other premium kits.

If I add your estimate of .015 to my starting SG, that results in an ABV of 14.3%, which seems about right.
 

Boatboy24

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The skins do make a considerable difference. I make sure to stir really well after adding them and also try to wait 8-12 hours before pitching the yeast and remeasuring SG then. I'll also take a couple more readings the first 24 hours after pitching, as it will often continue to rise.
 

sour_grapes

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Thanks, that gives me a better idea. Is your estimate per bag? This kit had 2 bags. There were a lot more skins than I've gotten with other premium kits.

If I add your estimate of .015 to my starting SG, that results in an ABV of 14.3%, which seems about right.
Every premium kit I have ever done (CC Showcase and WE Eclipse only) has had 1 large (~1.5L?) bag.
 

Wayne Freeman

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Every premium kit I have ever done (CC Showcase and WE Eclipse only) has had 1 large (~1.5L?) bag.
Same here, except for this one. It had two. I don't know if it was an error, because WE doesn't list kit inventories on their web site. I added them both, anyway, and it's tasting pretty good, even at bottling time!
 

Wayne Freeman

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The skins do make a considerable difference. I make sure to stir really well after adding them and also try to wait 8-12 hours before pitching the yeast and remeasuring SG then. I'll also take a couple more readings the first 24 hours after pitching, as it will often continue to rise.
That probably would help with the accuracy, but there will still be some undissolved sugars in those skins that them yeast bugs ("them yeast bugs" is a phrase I fondly continue to use 40 years after a university macroeconomics professor of mine used it while lecturing the entire class on how to make beer) will continue to chew on whether it's in solution or not.

I'm probably worrying too much about hundredths of a percent here and there.
 

Wayne Freeman

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1st I heard about this WE old vine zin having 2 packs.
Error or not, it’s a come-up.
Maybe they just divided the usual amount of skins into two bags. I don't know, this is my first time with this kit, but I do know that it was a huge amount of skins, compared to what I've found in the RJS En Primeur kits I've used.
 

dmguptill

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When did you buy this kit? I only got one bag of skins in the one I recently acquired. It was a pretty big bag (2L I think) but only one...
 

Wayne Freeman

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When did you buy this kit? I only got one bag of skins in the one I recently acquired. It was a pretty big bag (2L I think) but only one...
Sometime in late November or early December. My retailer had to order it from his distributor. Maybe they just used two 1L bags instead of one 2L bag. Neither one was as big as a 2L but altogether it was a lot. After adding the skins, it brought the level in the fermenter to a very scary level. Fortunately the fermentation wasn't overactive or it would have turned into The Blob That Ate the Winery.
 
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