Once in a while I am asked how I wet-finish, especially when possum is involved. Between 2000 and, oh, 2006, I asked weavers how they do it, and over the years I combined and fine-tuned it to based on the space/equipment/physical-height available to me.
Because these weavers were based in New Zealand, the answers concerned mostly wool or wool-mix, which suited me then. And it works for my cashmeres, even though the vendor recommends a gentler finish because cashmere doesn't full like wool. But as I started using silks and may eventually get to all silk, and I also have to replace my washing machine soon, I have been thinking more about wet finishing of all kinds, so I'm recording this here for my sake, although I did this once before, and it hasn't changed much, and in my Japanese blog more recently.
(My washing machine is a top-loader with an opaque lid which doesn't suit my control-freak-ness, so I haven't used it for wools except the spin cycle, but as this machine has been dying a slow death I'm compelled to ponder the top-loader-which-suits-my-stop-go-penchant vs. front-loader-which-saves-water-and-apparently-takes-out-lint-like-there's-no-tomorrow question.
I am always open to any recommendations/variations/suggestions; thank you in advance. Here goes:
1) I fill the sink/bathtub/container with the hottest hot water from the tap, (mine is about 55C) and dissolve wool wash or shampoo; fill with enough hot water to immerse the piece completely. (Some folks use kitchen detergent but my yarns are seldom that greasy as most are commercially spun and dyed.) Turn off the hot water.
2) I drop the piece in hot water and let it absorb the soapy water in its own time - maybe 15-20 min. If sections refuse to sink, I push it gently to coax; if in a hurry, I push the piece down gently and evenly all over.
3) I press the cloth gently all over so the piece completely soaks up the soapy water, then agitate a little bit to help threads come together.
From here, all depends on the weave/purpose/desired finish.
4) I may agitate some more, or not, then gently squeeze the piece to get rid of soapy hot water, put it aside, discard the water and fill the container with the coldest tap water, then turn off the tap.
5) I immerse the piece in the cold water, and gently agitate evenly, but I may continue for some time. I'm mindful about keeping things parallel/perpendicular. Then gently squeeze the piece to get rid of water, put it aside, discard the cold water and fill the container with the hottest tap water, then turn the hot water off.
6) I immerse the piece, and agitate. This is where dye, possum or mohair start come out, but also merino/wool visibly starts to full, so I observe the cloth vigilantly. Also the piece may not remain folded but spread out, squeezed, bunched together, whatever it takes to full evenly, not have creases, and, fingers crossed, still stay rectangular. Depending on the weave/purpose/desired finish, I work vigorously. Also, as long as the water doesn't fall directly on the piece, I may keep the hot water running so water/piece stay hot. I squeeze the piece to get rid of water, put it aside, discard the water and fill the container with the coldest tap water, then turn the water off.
7) I immerse the piece in the cold water and agitate. Again, I may have the cold water running as long as it doesn't fall onto the piece directly. Sometimes I stay in stages 6) and 7) longer, sometimes I repeated them. When satisfied, I squeeze the piece to get rid of the water.
8) Depending on the piece, I may fold it, or roll it in an bath towel, or fold/roll and wrap it in a towel, then put it through a full spin cycle. Depending on the piece, I sometimes start with a gentler spin, but more often I just let it have it.
9) I unwrap the package, steam press, sometimes with a cotton press cloth, on both sides, then lay it flat on wool carpet. (Cut pile works best; unfortunately my living room is now tiny loop pile so I sometimes dry it in the downstairs workshop on the old living room carpet.) If I'm not happy with how I've pressed, I'll even press it while on the carpet. Then I leave it overnight, or however long it takes, to dry.
10) When I peel it off the the floor it should be pretty straight and wrinkle free. But if it contains possum, it will continue to shed.
Wet-finishing guru Laura Fry demonstrates a dryer method, reminiscent to me of ye olde community waulking; I don't have a surface I can do this without much lining with plastic lining and moving of furniture, but when I did experiment with a small piece on a small surface, I still couldn't see the whole piece which made me uneasy and I haven't tried it with a bigger one. Here's another resource from her.
So far I've been washing my silk-mix pieces in a gentler version of above method; cotton and cottolin pieces are put in laundry nets and through the hottest and the most vigorous wash cycle, steam-pressed and dried either on a tube rather then a line, or on the floor.
EDIT: As I mentioned in the comment, I learned to weave at the end of the era when most/all weaving yarns still had scales left on. I wash superwash merinos in the same way still, but perhaps I need to investigate for this reason as well.