Does submerging the skins produce a result that is better than punching down the cap several times per day?
For red grape -- while a commonly stated reason for punching down the cap is to ensure it stays wet so mold doesn't grow, punching down physically manipulates the grapes solids and helps with extraction, as well as adding O2 that yeast needs to reproduce. For all these reasons it's a necessary and beneficial process. And for red grape -- the amount of pomace makes it impractical to weight it down -- the following picture is the pomace from 150 lbs of Merlot on the base of a #40 press:
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However, in this thread we're talking kits with skin packs, which are much lesser in grape solids volume. The following picture is 6 skin packs from 3 Forte kits, in a 32 gallon Brute:
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It's a LOT less volume, so the idea of submerging the bags is possible.
My method: I used a stainless steel paddle and pushed each skin pack down to the bottom and scraped it along the bottom, stirring up any sediment, and roughing the bag but not to the point of tearing it. This was repeated 4 to 6 times for each bag.
Side Note -- Last year there was question if the bag limits the maceration by clumping the skins. IMO no, as the bags are not tight and were easy to manipulate and the pomace inside was moving freely. When "pressing" the kits, I held each bag over the Brute and let a lot of liquid drain, then hung each inside a 6 to 8 gallon fermenter to drain for 10 minutes while I was pumping out of the Brute. I recovered several liters during draining, and later pressed the bags, recovering an additional 1.5 liters of wine. Wine flow through the pomace appears good. Punching down 3 times per day helps with this.
Will weighting the bags down provide the same level of manipulation? I doubt it -- In my case "punching down" each Brute took about 5 minutes -- who is stirring for 5 minutes each time? I admit that when making reds from juice and whites, I don't put as much effort into stirring, probably a minute per fermenter each time (typically 3 times per day). Seeing the pulp and/or skin packs gives me a bit more ambition.