338. The Wine Vat

47:7 When grapes are pressed in a vat, juice flows from them, so the entire contents of the vat is considered wine and becomes prohibited if handled by a non-Jew before boiling. This is true even if he only touched the seeds or the skins. Therefore, vats of pressed grapes in a non-Jew’s home are prohibited because he may have taken some wine from the vat, rendering the whole thing impermissible. One may not press grapes at a non-Jew’s facility even if the vat is sealed.

47:8
One should be careful not to have a non-Jew remove the seeds and skins from a vat, even after one has removed the first and second batches of wine, because drops of wine may still remain.