Clear coat on interior walls over PMF (bed sheet)

[TimC]

I applied cotton bed sheet to the interior rigid foam walls with TBII. I was originally going to paint over that but the pattern on the bed sheets really popped with the TBII and I might just leave it the way it is. When it is completely dry I might change my mind but right now it's dry to the touch and it looks really nice.

I'd like some ideas on how to clear coat those surfaces. I've thought about water based polyurethane which is one of my favorite wood finishes but not sure how it would mate with the texture of the TBII and fabric. Some testing may be required. Anyone have any other solutions?

Thanks, Tim

[Pmullen503]

I'd go with the WBPU. The question is how glossy.

[TimC]

I did a test on some scrap foam and fabric. Sunny with high in the upper 80s so TBII and WBPU dry very fast, probably too fast since I put them in the sun. Anyway, the result is good. I used matte finish. I wasn't too fussy with the application, just wanted to see an example of the three materials. Three coats of PU seems to fill the bedsheet texture pretty well. I'm not looking for a smooth finish, just good enough for the interior walls.

Thanks for the advice Pat. The fabric isn't camo. I'm not really a camo kind of guy. It's more like a Monet canvas : )

Now I have to figure out how much poly I need. Three coats could be at least two quarts. I have interior paint which will cost nothing but my labor!

Sample


Interior wall without finish. That hole (light colored area without TBII) is an egress window. Not a door. I am going with one door since this is a solo camper. Egress window was a third of the cost.

[Pmullen503]

I like it. Not too dramatic a pattern and color, better for sleeping.

[Mark Gunter]

Hi Tim, I see you did your own test so no longer after advice, but I was just going to say WBPU would be my finish of choice for that, satin or matte finish. Hope all goes well with the build.

I like using that stuff for certain projects myself, the fast drying time and easy sanding properties are big selling points. Application needs to be quick because of the quick flash rate, I put it on in long, wet strokes, because if you try going back a bit it will already be flashing out. Get a full coat on, leave it alone for bit, sand and repeat.

[TimC]

Thanks for the encouragement Mark. Right now I'm finishing up the PMF on the outside of the walls.

The test piece ended up kind of rough compared to how a first coat raises the grain on wood. I'm going to continue the test with a good sanding and another coat or two of poly. I'm not sure how the surface will turn out. I'm might do half with another coat of TBII to fill the weave a bit more and compare how it effects the finish.

[KCStudly]

Woodbutcher used untinted paint as a clear coat on one of his fabulous wooden builds. He seemed happy with it.

[Mark Gunter]

“Untinted paint”, yes, I call it “clear paint” - untinted dark base. The dark base of most mfrs is pretty clear or translucent, and for exterior projects like shutters or whatnot a good quality exterior dark base gives you better UV protection and resists mold, mildew and cracking/peeling better than polyurethanes. I’ve never seen the need for using clear paint on interior projects, interesting.

[TimC]

That's interesting about using the paint base. I might look into that in the future if I have a similar project.

What I ended up doing was sanding the wall and recoating the interior bedsheet with another two applications of TBII (cut 50/50 with water). It darkened the surface a bit and it actually looks good. It isn't a smooth finish like a semi-gloss or gloss poly would give it (eventually) but I don't need it to be perfect. Yeah, the other reason I went with the TBII is I had a gallon from Menards at about $17 after rebate and the WBPU is $23 a quart. I have just enough WBPU from a previous project to finish the cabin and galley woodwork on the foamie build. Coating the interior walls would have required close to a quart.

Thanks for all the suggestions!

Tim