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Pre-cat over shellac primer2/18
I started a job using the Bin alcohol based shellac primer (red can) on a couple of sheets of MDF and now i have to shift gears and use a different top coat then planed. The top coat will be Sherwin Williams pre-cat lacquer and the primer for that will be the sher-wood pre-cat primer surfacer E63W30. Can i put the new primer over the old primer? If the consensuses goes back and forth i will just buy new sheets.
Re: #2. The beaded MDF panels that my supplier has are not primed. The entire finishing process is under my control. Check with multiple suppliers if necessary to find what you want.
Give the pre-cat primer a try over the BIN. If you are thinking to replace the sheets anyway, what's to lose?
Trial it thru the full finish schedule.
We use the Sealcoat purified shellac as a barrier layer all the time under pre-cat clear sealer with no problem unless we go heavy on the first sealer coat.
We did some vanities that the cab shop had installed pre-primed beadboard from one of the box stores (think H-me Dep-t)
The factory primer crinkled under our lacquer primer - Valspar pre-catalyzed sanding sealer tinted grey. We sanded the crap outta them and laid down successive piss coats before a flow coat to insulate the factory primer. It worked, but was in and out of the booth 3 more times than expected.
Now, when asked to quote such stuff, I put in a caveat upcharge for the 'unknown' behavior of pre-primed stock.
Sealcote works for me! 45.00 per gallon.
Be careful with Sealcote under water based finishes. It is supposed to be fully compatible but sometimes the chemistry that gives it a long shelf life causes problems. I always make up my own dewaxed shellac and don't have problems.