As explained to me by a chartered loss adjustor 3 months ago.
If you use a disclaimer ,and have WRITTEN procedures for cleaning each type of fabric, and then follow that procedure , the customer has no claim against you in the event of an adverse outcome.
No disclaimer, no written procedure and an adverse outcome , the customer has a valid claim whether your fault or not.
As with most work based activities now , it is not sufficient to do the job correctly, you have to be trained, and document what you have done and why... think social work, banking, politics,medicine, teaching, carpet cleaning. The principle is the same.