Lusterboard/SignPly Sealant

[Liesl Dexheimer]

I'm working on making my own 4'x3' sign to replace an older sign I had someone else make years ago. They used Lusterboard/SignPly and I'm using the same material (it has a white aluminum face). I won't be using edge caps on this sign. The company that made my sign a long time ago also didn't use the edge caps but just used a sealant. It held up for about 7 yrs but now the plywood has completely rotted away. My question is what kind of sealant should I use?

[Joe Pelonio]

I have sanded, filed voids, primed and painted the edges of 1/2 MDO and had it last as long as 15 years, though the vinyl lettering was bad by then. Just exterior gloss latex. One-Shot would be even better if you have some handy, I wouldn't buy it just for that, though. Lusterboard usually has smoother edges with few, if any voids. I like to sand it convex so the rain won't remain on it, especially the top edge.

[Rodger MacMunn]

I've never used Lusterboard, but about 12 years ago I bought 10 or 12 sheets of a similar substrate. Since I rarely do a square or rectangular sign, I used Elmer's Squeeze n'Caulk ( paintable silicone) to seal the edges. I'd used this on MDO plywood for years, with no failures, but that other stuff failed miserably .... all but 2 of the sheets delaminated & the wood rotted. I still use the Elmers on some signs, but I also use a couple of coats of white exterior wood-glue, applied with a wet finger. Nice & smooth when dry ... ready to prime & paint.
Wood moves from moisture migration & metal moves from thermal expansion, & I suspect this contributes to the early failure because somehow, moisture got in there.

[Liesl Dexheimer]

Thank you for the suggestions. I'll let you know how it comes out.

[Ross Moshinsky]

Just out of curiosity, why not go with 6mm ACM? Back to back it would be the same thickness and you wouldn't have to worry about rot or edge treatment. Cost would have been just about the same as well.