Duratex Over PL

[David Carter]

The picture below is a view into the horn of the DR250 I'm currently building. The black surface on the right is the horn sheath. The black surface above is the bottom side of the horn brace. The bare wood to the left is the side panel which then mates with the curved back sheath. The spot where the duratex has peeled is where the back sheath meets the curved back brace (can't remember is that's the terminology used in the plans, but I think you know what I mean).



Yesterday I painted the inside of the back sheath with duratex and let it dry for several hours before attaching the side panels. But duratex apparently doesn't stick well to PL. Due to the awkward location of that joint and the fact that I had to force the PL down into it by sliding my finger across it to fill gaps that became visible after the initial gluing had dried, I wasn't able to chisel the PL off of that joint so it is covered with a thin layer of dried PL. At the time I thought it wouldn't be a big deal to just paint over it since it was way back in the horn and wouldn't be noticed as long as it was painted black. But apparently that isn't going to work.

Any ideas on how to get that joint to stay black? Do you think it would work to wait until all the surrounding areas have been completely duratexed and then spray over the bare PL with some black spray paint? I've got regular spray paint as well as the kind that's made specifically to adhere to PVC and other plastics. If you don't think that will work, what else do you think I should try?

Thanks.

[Tim A]

I just ran into the exact same thing with my monitor build. This is the first time I've ever had a problem with Duratex sicking to PL. It's also the first time I ever used the Hi-Build. Is your's Hi-Build?

At any rate, latex paint will stick to the PL, and Duratex will stick to latex paint if it's not glossy. Touch the area up with some flat latex and let it dry, then go over it with Duratex.

[Sydney]

Have you tried touchup using acrylic latex flat black applied with an art brush?
ie Liquitex or Winsor & Newton from an art supply like place like http://www.dickblick.com/categories/acr ... tsacrylics
Straight from the tube, it is very thick and can be built up (impasto). or thinned down with water.

[David Carter]

I just ran into the exact same thing with my monitor build. This is the first time I've ever had a problem with Duratex sicking to PL. It's also the first time I ever used the Hi-Build. Is your's Hi-Build?

At any rate, latex paint will stick to the PL, and Duratex will stick to latex paint if it's not glossy. Touch the area up with some flat latex and let it dry, then go over it with Duratex.

Mine is indeed the Hi-Build. It's my first experience using Duratex, and I chose hi-build based on Leland's recent recommendation. I'm using a medium nap roller for the base coat and a textured roller for the final coat. Very nice, but the PL issue caught me by surprise.

I'll try to dig up some flat latex paint and give it a shot. I've got a bunch of leftover paint in the garage from various house projects. I know I don't have black, but, if I'm going to go over the latex with Duratex, it doesn't really matter what color it is, does it?

Thanks for the tip!

[Tim A]

Color shouldn't matter.

[David Carter]

Have you tried touchup using acrylic latex flat black applied with an art brush?
ie Liquitex or Winsor & Newton from an art supply like place like http://www.dickblick.com/categories/acr ... tsacrylics
Straight from the tube, it is very thick and can be built up (impasto). or thinned down with water.

Good idea. My wife has tons of acrylic paints for craft use, and I'm pretty sure she's got some black. I'll try to dig it out of the closet this evening.

Thanks!

[Mark Coward]

I just used black spray paint for those areas in my DR's. As long as it's black it's not going to show, you don't have to use Duratex there.

[David Carter]

I just used black spray paint for those areas in my DR's. As long as it's black it's not going to show, you don't have to use Duratex there.

Thanks, Mark. That would definitely be the easy way to go.

[David Carter]

For the outside of the cab, I ended up painting over all PL lines with acrylic paint before laying down the first coat of Duratex. On the insides of the horn where the Duratex had peeled away, I sprayed with black spray paint. It was easier than reaching all the way back there with a brush.

The only issue I've had is that I've found several spot where the Duratex seem to get brittle, cracks, and flakes off leaving small spots of exposed wood. Not sure if it's because there were air bubbles that dried without having adhered to the wood or what. I've gone back and touched up with a foam brush. We'll see if it lasts.

[LelandCrooks]

Typically that's caused by a solvent, grease, or oils from your fingertips on the wood before you start to finish. You can't see it, and didn't know you did it. I always wipe everything down with thinner before applying any kind of paint. Wait about an hour before applying duratex. Better yet, after your final sand, wipe it down and apply the next day.

[DAVID_L_PERRY]

I have had a couple of areas knock off where I used the UK Aldcrofts speaker paint directly onto parts of my cabs with filler (car body type filler).

Before I paint I always clean the bare cabs with a vacuum cleaner and then wipe the whole thing down with white spirit and then leave them to dry for an hour or so before painting.

All I can think of doing next time is to roughen the surface up far more than I would normally do to give a better key...

I have not had problems with it adhering to the PL but then its in an area that should get no knocks and scrapes.

Dave

[David Carter]

Typically that's caused by a solvent, grease, or oils from your fingertips on the wood before you start to finish. You can't see it, and didn't know you did it. I always wipe everything down with thinner before applying any kind of paint. Wait about an hour before applying duratex. Better yet, after your final sand, wipe it down and apply the next day.

So am I wasting my time trying to touch it up without doing something else to remove the offending substance? Can I carefully wipe those spots with thinner even if a little gets on the surrounding Duratex?

[LelandCrooks]

Yep. Then sand them and the surrounding area a little to make sure you have a good tooth for the dtx to grab on.