Eve, so sorry to hear that you're not happy with your Cotswold Stripe Mat and that you've found it to leave black marks in your washing machine. This is not a problem we've ever encountered with the mats before, nor should it happen. Turtle Mats are designed to be happily washed repeatedly at 40 degrees, so I can only imagine this to be a rare faulty mat. If you'd like to get in touch with us directly here via info@turtlemat.co.uk (and mark it for my attention) we can discuss in detail next steps in getting a replacement out to you as soon as possible.
Apologies again and best wishes, Becca
Rebecca Wilson