Filling Grain with Automotive Polyester Primer

Advice on using polyester auto-body primer to fill deep pores in Oak. March 28, 2012

Question
Can anyone recommend a grain filler for oak?

Forum Responses
(Finishing Forum)
From contributor R:
Do you want to fill the pores with your clear coats or are you looking to fill the pores with a contrasting color and then apply your clear coatings on top?



From the original questioner:
I want to fill the pores, then paint over so you canít see them. The catch is that itís oak.


From contributor H:
Polyester auto-body spray primer. Two to three coats and a 120 sand will fill the heaviest oak grain.


From the original questioner:
Just spray it three times and sand, or sand between each coat?


From the original questioner:
Can you recommend a manufacture or brand?


From contributor H:
Sorry I do not have a brand. It is standard in the body shop business, so find an auto paint supplier and they should point you in the right direction. They are normally thinned with acetone and the cat is MIBK. Do not get this stuff in your eye's as it has a habit of crystallizing them - wear glasses. Spray with a gravity gun and fog on your first coat, the let it tack and then lay it on in 1 mil increments. It sands like a dream. It is a universal primer, meaning anything should go over it. It would pre-fill any damage and sand. Next spray on the polyester, let dry then grind down and re-fill damage with 3M's blue speed putty. Re-sand then finish with your normal primer.


From contributor G:
So it is a two part process, it sounds like the polyester is a second step? What am I spraying before the polyester? The blue spread putty - is that for deep grain or is that to be applied over the entire area?


From contributor H:
One step directly over wood after you have caulked and filled for damage. The polyester will cover all the grain but when you sand with 120 you will find holes and nicks that the speed putty is designed to fill. Get the stuff out of your gun in about 15 minutes or throw your gun away as it will become a boat anchor.


From contributor R:
It helps to block sand the raw oak prior to applying your chosen coating. 120 or 150 will give you a head start. I suppose an air sander would work but I like to wrap the paper around a hard and level surface. Too bad you couldnít opt for another species of wood for the paint grade project.


From contributor Z:
We use only ML Campell products but they have a product called level sealer that is awesome. We spray three coats, sand with 220 and then use a Festool sander on flat areas. The other areas we sand by hand. It works great.