I've used Rayon (Madeira) since 1992 without any problems, I even regularly use the first handtowels I ever embroidered without any problems. I did not use poly until 2003 or so. As washing powder does not contain bleach here I have no idea if either of them it would fade.
Depends on the design I'm doing. I will use rayon only on a project because the thread is so pretty. I use poly on a project that might be bleached like napkins. You can bleach poly, but bleach will fade rayon.
I am using Royal thread for years and never had any problems.
Hugs - Roberta
I use about 95% Rayon (Robison Anton). I had problems with bleeding of red and dark green but it was a less-known brand and maybe polyester. I threw it away - lesson learned.
I do recommend poly on white towels and baby bibs so you can bleach if needed.
I love Royal thread. It has a nice sheen and just seems to go and go without breaking. always recommend it to people as excellent thread that is really good value for money. Never had any problems with colours running.
Hope that helps. Cheers Lynne