Turns out my conclusions were wrong about pink stains. The vinyl companies have apparently admitted now that it's a chemical reaction.
http://marinefabricatormag.com/articles/0514_f2_vinyl_discoloration.html
June
We have been thinking it was some kind of mould for years.
Suzi
"polyurethane foams, use polyolefin" how would I know what foam is on the boat im not a chemist
"Elevating the cover fabric from direct contact with the vinyl will also allow for airflow underneath the cover and will prevent high heat buildup in the vinyl itself. Rampey suggests another layer of fabric or perhaps a nonwoven backing might help, or something as simple as placing a swimming noodle under the cover on a boat deck to elevate the cover and increase airflow."
sometimes this is impractical like over a rear sun pad where it really has to lay against it. if I left it loose it will puddle water.
"If a seat is properly constructed, with the right materials, and cared for properly by the dealer and the boat owner, pink staining is not likely to ever be an issue"
I can see if the customer got this info how I could have a problem stating I should have know and demanding it to be redone with proper materials :(
migration from adjoining fabrics or foams etc doesn't explain pinking appearing in the middle of
PVC hoods we make in the UK ?