H--
I've laundered many a piece of 18th and 19th century silk. Chemicals associated with dry cleaning, and I don't care whose dry cleaning we're talking about here, are harder on silk than handwashing. If you have an early vintage scarf prone to bleed dye, if you don't have time, or if you're just too terrified, take the scarf to a specialty cleaners immediately. Otherwise, you're really best off doing it yourself. Spot cleaning will often leave marks if you do it yourself, so you probably will just have to gut it up and wash the whole thing. I've never had luck with spot cleaning, so if someone else can jump in here...
Some detergents are easier on protein-based fabrics than others. I buy a specialty silk wash from Le Blanc, which I'm 99.99% sure is overkill. When I'm really in a pinch I'll use Woolite, under the assumption that wool is another protein-based fiber like silk, so it must be better than something like Tide.
Makeup stains are part of life. S**t happens, so just get it clean as soon as possible. I've seen the instruction scarf. It looks unlikely to run/bleed dye. Don't even get me started whining about a lace shawl from 1720 that I smeared Chanel red lipstick on. I'm still p**sed off about that one. Anyway, makeup does come out, H.
1. If the stain is bad, put a little bit of woolite or silk wash directly on it. (don't do this with early vintage scarves, since they may bleed more)
2. Run a sink of tepid water with the chosen detergent in it. Don't get the water too hot. Your hands shouldn't really register the temperature as much of anything.
3. Soak scarf for 5-10 minutes. Check stain. Keep soaking if stain isn't out. Avoid rubbing stain. Avoid handling scarf as much as possible. Do NOT pick up the scarf by an edge or any small part of it while it's wet. It's best to hold all of it in the palms of your hands as much as possible while it's wet so you don't stress the fibers. I check stain removal by floating it flat in the water and looking at it while it's still floating.
4. Rinse, rinse, rinse. You have to get the detergent out. I soak mine in clear water over and over. I'm really OCD about it. NEVER, NEVER, NEVER use vinegar in your water. Sometimes people will recommend it to you, but vinegar is acetic acid. It's a mild acid, but it will still eat away a little bit at silk fibers and can leave you with a very subtle "fuzzy" look to your scarf. You won't realize why. Trust me on this and learn from my stupid, stupid mistake.
5. Dry flat on top of a terry cloth towel. They don't take long to go from soaking wet to damp. I dump the silk from a ball in the palm of my hands to a flat, towel covered surface, then I very gently spread it flat without lifting it up anywhere or tugging very hard on any one edge or small space.
6. Press while still damp. I usually start within 2 hours of laying the scarf out to dry, and it's pretty humid in my part of Alaska.
7. This is critical--Put a terrycloth towel on top of the ironing board. Use silk setting. Press on the reverse side. Press from the inside to the outside. Stop before you get to the hems and follow GF's brilliant hem rolling advice. This is a variant of Quinn's Mom's instructions. I've never had any luck at all pressing through a top layer of towel.
8. If you're just pressing the scarf and don't want to savage the poor hems, press them on the reverse side on top of a terrycloth towel. The towel has enough give that the hems have somewhere to go rather than go flat.
I've used similar techniques with 18th c. silk lace and 19th c. silk-on-linen embroidery. People were washing silk long before dry cleaners existed. Just be careful not to a) drag the piece of wet silk out by one edge and b) use too harsh of a detergent and you should be fine.
PM me if you need to be talked through this. I curated a small collection where I had to be conservator too. A modern silk scarf isn't nearly as nervewracking after that.
We'll get you through this, H!!!