To seal or not to seal

[Homer]

My jobber says that when you use the new urethane primers you really don't need to. I seal every thing with epoxy then use urethane surfacer, so after sanding with 400 to 600 do you guys think it is needed. It will be a white top coat bc/cc with blur stripes.

[Bob K]

You use a sealer when you NEED a sealer. You don’t need a sealer in a lot of situations. If you are painting over good original paint you don’t need a sealer. If you are painting over good surfacer that has been blocked without sand throughs exposing the other material under it then you don’t need sealer. If the side of your car looks like a Palomino pony then sealer would be in order. You know, a little spot of epoxy primer hear and there, some filler showing through the sanding and maybe an area of etch primer on freshly sanded steel. Sealer gives you a uniform color and texture for your paint to be applied to. If you are using cheap paint then a sealer close to the color you are painting helps you get a nice uniform coverage with less paint being applied. Also if you have sanded through some previous application of base coat you might get a reaction between the new base coat and the feather edge of old base coat so a sealer would help there.

Bob K