I have seen on the SPI TDS as well as some training documents from PPG that after block sanding a urethane primer-surfacer, it needs to be coated with something, and not just left in a sanded state for any length of time. Some documents say that if left sanded more than XX number of hours (or days), the primer needs to be scuffed with a scuff pad before applying another product.
I would like to understand why this is required...what happens to the sanded urethane after it sits? Do the sand scratches change or does the primer develop a film preventing adhesion?
I'm going to be doing my block sanding in sections as I don't get as much garage time as I'd like, so I want to figure out the best plan possible to avoid problems or waste of product.
Thanks
Michael
I would like to understand why this is required...what happens to the sanded urethane after it sits? Do the sand scratches change or does the primer develop a film preventing adhesion?
I'm going to be doing my block sanding in sections as I don't get as much garage time as I'd like, so I want to figure out the best plan possible to avoid problems or waste of product.
Thanks
Michael