I am making a sign that will sit outside for an animal shelter. We are nervous about it holding up to the elements. We were planning to make the sign out of maple and then glue on the plywood words. (It kills me to say we are going to paint the maple so it matches the rest of the sign display) Does this affect the hold of the glue? Does 1/4 Birch Plywood from Ocooch Hardwoods last outside? Or does hardwood hold up better? And how to we finish it spray lacquer, poly? Help please. TIA
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Welcome back! Good news, you’re not the first to ask, so you can find the answers with a little digging in a search:
https://community.glowforge.com/search?q=Outdoor%20sign
Everything you need is in those threads 
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I just poked around those threads and didn’t find a particularly clear answer, but I’m curious of this question too – so I hope we do get some fresh discussion on the topic.
/sub
Cheers.
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IMO - I would not use plywood for any of it if you can avoid it. Water will find it’s way in and ruin the sign over time. If you could use Cedar or Teak you’d have a better go of it - that just weathers over time.
Personally if you’re going to use hardwoods, finish the piece with several (5-7) coats of spar urethane. It has properties that help minimize UV light which will break it down. I built a teardrop trailer out of hardwoods and ply and sealed the whole thing with lots of coats of spar.
When I was 16 I spent a summer scraping my boss’s wooden boat down, sanding then sealing with many coats of spar urethane. It lasted on the water 5+ years before he had to do it again.
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And that’s kind of the point. There is no one size fits all answer for this, any discussion we’re going to have will be full of theoreticals and caveats. It will come down to your materials, your specific situation — placement of the sign, expected weathering, expected UV exposure, aesthetics, and other factors. There’s no easy way to say “this is the right way to do it”.
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That’s because it isn’t a FB post. I believe there are many folks there who easily say that their way is the only correct way 
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I have personally found MDF (“Draftboard”) to be the most stable product for anything outdoors. I’ve got “hex signs” on my daughter’s barn/shed and my own that are coming up on 20 years now, painted with unknown cheap acrylic craft paint from Wally or similar.
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I think it is the coating that is the real star here. Any moisture through the coating into the MDF and it will swell and disintegrate.
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This is one of the best products to use for outdoor signs. 3 coats —lightly sand between coats. Follow the product instructions and do not rush the process. Also purchase a bag of various widths of sponge brushes.
If possible try to keep the sign away from direct sunlight because the wood will fade.
Also between poly coats put the sign in your garage to dry. Insects just love to attach themselves to wet poly.
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I do a lot of “welcome” porch leaners, and although the leaners themselves are wood planks that have been stained with outdoor stain, the letters and interchangeable ornaments I make out of draftboard, which are painted with the cheap acrylic craft paints. I’ve been selling them for over a year and haven’t had any complaints about them not holding up in the weather. That might be because they are on porches, but I have no idea if those porches are covered or not, but even my porch gets wet when the wind blows the rain. We do use a poly spray for the backs to help protect them from the weather.
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Got any pics, or have you already posted them? Not sure I saw any previous posts.
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If it’s for outdoors, and the wood is going to be painted, why don’t you take a look at Acrylic in the colors you desire instead? Acrylic will last significantly longer exposed to the elements than wood will, even if the wood is painted or sealed (maybe not if you epoxy coat it, though that’d be a lot of work).
You can use a sheet of Acrylic for the backboard, and cut the letters from colors you want. Acrylic can be easily bonded (not glued - Acrylic is stuck together using a solvent that causes the mated surfaces to “melt” together).
Alternately, there are non-Proof Grade (but just as good, IMO) Acrylic panels from other suppliers. I like the looks of a type that has a colored face layer with a different color below the surface, so you could for example engrave white letters on blue without painting, by buying the Acrylic with a blue face and white underlay. This approach requires nothing be glued to anything else…
Like this:
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My 2 cents worth after making far too many outdoor projects to count: It’s not so much the material as it is the finish. The spar urethane suggested above is the right product.
As for solid vs. ply: I’ve dealt with with a lot as well. Since we are talking about a sign and not a piece of outdoor furniture, solid of any species is less stable and subject to movement (read cracking and warping). Plywood, going outdoors, should be marine grade if the budget allows, exterior grade, if not. Use lots of spar. Nothing lasts forever, but this will give you many years of useful life before a re-finish will be necessary.
For raised letters (approx 1/8") on the plywood: Painted draftboard (MDF), acrylic, or wood will all work. Just use an outdoor rated glue (Titebond 3) or epoxy. More spar! Lots of spar!
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Following up on randy.cohen’s post, you can also get the two-part engraving plastic in many different wood prints. It would give you the look of wood, without all of the associated problems.
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Since I hadn’t notice that kind of material before, I clicked through to check it out.
The data sheet specifically says “no” on “UV stable” and “Outdoor Weatherable”. They state “rotary engraving” (meaning CNC). The material itself is ABS. ABS does not laser very well, if at all. Also, lasering ABS produces Cyanide gas. Won’t hurt the machine, but kind of bad for you if you have exhaust leaks or anyone outside downwind of your exhaust…
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The sheet I saw says they are a modified acrylic, should laser pretty well?
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Yeah, I just selected the first two wood prints I happened upon. The oak print is recommended for rotary and not UV stable. The walnut is for laser or rotary and is UV/outdoor rated. There are plenty of wood prints on the site that would work. I’ve used many of them.
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Since the walnut print was the first one I listed in my post, I’m curious as to why you didn’t check the “stats” for that one. ;oP
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Just to be sure that we’re talking about the same thing… I am looking at this:
which links to the SDS here:
https://www.jpplus.com/mwdownloads/download/link/id/554/
and it says:
PMMA is acrylic. They seem to have impregnated some of it with styrenes (possibly the top layer? IDK)
Maybe their other products in the line are what you were looking at?
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