I think years ago it was quite a common thing to remove fine buttons from garments before dry cleaning. They were resewn onto the garment afterwards. Nowadays, it seems totally unthinkable to make that kind of concession to our buttons!

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I used polymer clay buttons on my handknit sweaters for years. In fact, it's the reason I originally started working with polymer clay. When people raised concerns about machine washing and drying, I'd remind them that a handmade wool sweater shouldn't go into the washer and dryer anyway! It should be handwashed and laid flat and smooth to dry. When people put the button care into context with the sweater care, the objections were erased.
Having said that.....I'm always asked how durable my horse pins are, especially since I use a backfilling technique (similar to scrimshaw) to accent the carved areas. I always said they should not go through a wash-and-dryer cycle, but that I've worn them on my coats through New Hampshire spring (rain!!) and winters (snow! ice! sleet!) and I've never had the finish wash off.
Then one day I accidentally washed a top with a horse pin. It DID go through the washer and dryer cycle. And came through completely unscathed!! Just a little cleaner....
But I still wouldn't RECOMMEND it!
hope this helps.
Luann