I think it would be fine to do it in the sink, as long as you rinse the sink out with bleach afterwards, considering the formaldehyde content. I'm using my biggest stainless steel stockpot and then washing it with bleach after all the fabric is out of the pot. I'm also going to rinse the fabric one last time in a hot water cycle in the washer. That way, if there's anything left on the fabric, it can be rinsed off afterwards.