Paint Sealer Problems

[Lito1942]

So the theater I am working at is remounting a show and we had to repaint the set because it was just battered up on its last tour. We color matched and painted over scratches and the set looked brand new. So it was time to seal it, and when we applied the sealer to the set many of those scratches that were covered began to show through again. We thought it was because we were applying the seal with brushes, so we sprayed it on and got the same result especially with the white paint. The white paint we are using a household latex paint. Can anyone explain why this happens and if there is anything that can be done about it? Thanks

 

[Les]

A few things off the top of my head since I used to mix paint for a living:

-Color matches never turn out perfect. There will always be a slight difference in the formula even if it 'looks right'.
-As an addendum to the first point, the new paint may be of a different brand or new base formulation (paint constantly changes year-by-year).
-The old paint could have become porous over the years, which is allowing it to absorb the sealer more readily.

I feel like it could be any of these things, or a combination of all three.

 

[josh88]

Les sounds on point to me, and the two of us have similar paint experiences. I'd add too that he mentioned color matches always being slightly different and that base formulas change. Even going into a store with a color you got two years ago the paint company may still have that same color but because the base has been reformulated a different combination of color might make up the new version. so it may actually be the "exact" same color but what makes that color may have changed, which could produce different results. So color matching by hand is rough because even with the precision of machines it can be tough.

I would place my money on porosity and different paint makeup. How glaring is the difference between the old and new?

 

[JLNorthGA]

Did you sand the scratches to feather them? Whenever you do a top coat over existing paint (or stain or finish), it is important to even out or feather the scratches. Put it this way, you have a canyon (gully or whatever) in a flat plain. Until you even out the edges and make the walls of the canyon less distinct, you won't be able to hide the canyon. If I ever have to paint over scratches, I usually sand it with 150 grit and then 220 grit sandpaper. This gives a more uniform surface on which to apply the paint. I may seal it first, but I always sand it.

 

[Lito1942]

We filled in and sanded down the deep scratches and those are fine. The marks that are coming through after we seal are the black scuff marks.

As far as our color matching Josh, there is not a glaring difference between them.

 

[JLNorthGA]

We filled in and sanded down the deep scratches and those are fine. The marks that are coming through after we seal are the black scuff marks.

As far as our color matching Josh, there is not a glaring difference between them.

Black scuff marks and Sharpie marks are tough. I usually use the oil based Kilz on those. I usually get bleed through with latex based Kilz and other primers. You can try scrubbing them off with Goof Off or similar products prior to painting. I've also had good luck with Zinsser BIN primer.

YMMV.

 

[beachbum]

if you can work it out, a light coat of silver paint will also kill sharpie and other markers, as the metallic content blocks the marks from bleeding through