great responses and replies!
Thanks for all your input.
These are Niagara grapes, the cousin to concord grapes.
Welches uses them to make white grape juice.

Destemming by hand was VERY time consuming,
but now it's fermenting, having pitched it with cotes des blanc yeast.
I chaptalized it, added sugar until it was about 13-14% p.a.v.
the cap is pushing to the top and is made of all that very small and fine
sediment.
I will probably scoop it off soon. It's somewhat clear underneath.
I think most of it will drop out afterwards.
Next time I think I will just pick off the bad grapes and crush by foot
(hopefully no toe jam!)
or a 4x4. Im thinking of building a crusher....maybe a good winter project!

Thanks again!
Rick