So I’ve never heard that the wine becomes only wine again once it dries? Can anyone confirm this?
To expand a bit on what
japhy wrote, it’s a little more complicated than that. In it’s simplest terms, it’s the stain, which is most noticeable when red wine is used, but the principle applies equally to white.
If, for example, a chalice tips and there is a spill on a stone floor, the spill is to be mopped-up with a purificator as soon as possible. Once the purificator is rinsed in the sacrarium, the matter is closed. But if it was a carpeted floor, other steps need to be taken. Once the spill itself is removed as above, the area of the carpet must be cleaned with clear water, which is to be absorbed into another purificator in order to eliminate as much residue as possible. That purificator would then also be rinsed in the sacrarium. (The purificators are then laundered normally.)
Anyway, what’s left when the carpet dries, whether the spill was attended to not? A stain. If the spill was properly attended to, it’s just a stain, and the carpet should subsequently be shampooed to remove it (just as the jeans should be laundered normally). If, however, the spill was not properly attended to, the stain becomes problematic. As long as the nature of the “accident of wine” (in Western terms) remains, the Real Presence remains too. When the nature of the “accident of wine” changes (if, for example, the wine sours and turns to vinegar) it is no longer wine and thus it no longer contains the Real Presence. (Wine does indeed sour, and it’s one reason why the Sacrament is not reserved in that form.) Admittedly, with a dried stain it’s a bit more difficult to tell the status of the “accident of wine” but it is always preferable to err on the side of caution and treat the dried stain as if it were still fresh.
Hope that helps a bit and hasn’t added to the confusion.