Weatherproofing MDF for outdoors???

[Mohammed Issa]

Hey guys,

I got a request to laser cut the word "JOY" with the nativity scene inside the O.
My table size is 600mm x 900mm, so I'm going to pretty much cut each letter to the max size I can.

The question I have is what is the best type of wood to laser cut that is easy enough to cut (not too thick) and easy to weatherproof, then paint red?

I know MDF is probably the worse of all options, but as it is quite cheap, is it possible to weatherproof it?

any advice or recommendations?

Thanks!

[Scott Shepherd]

If it's like that sign and it's temporary, you can certainly seal it with shellac and then paint it. It'll last a while, but not ideal by any means. I've done interior stuff like that, as per engineer's specs, but not outside. I know the inside stuff I did, we painted with automotive grade paint and that stuff did really well. It's in a hotel lobby, still there a couple years later.

[Art Mann]

My opinion is that cheap big box store MDF can not be sufficiently waterproofed to prevent it from being damaged with minimal exposure to the weather. The material I would use is sheet PVC that is used as a premium grade trim material in the building industry. It is made to hold up in the weather for decades, it is very easy to cut and is designed to readily accept exterior latex acrylic house paint. The material is something like $125 a 4 X 8 sheet of 3/4 inch thickness. There are formulations of MDF that are weather resistant but I haven't tried them.

Edit: The Engraver's forum has become almost exclusively a laser cutting and engraving forum. I just realized that forum is the one I was in. I will leave the post in place but I don't think PVC is suitable for laser cutting.

[Kev Williams]

Why not get some Coroplast in red? Cut it and be done with it- it's meant for outdoors and it's dirt cheap...

http://www.engraver1.com/erase2/coroplast.jpg

[Steve Jenkins]

Exterra is an outdoor mdf that holds up quite ell. I made some column wraps for our storage shed and they have held up well fo 2 yrs so far.

[Gary Hair]

Do yourself and your customer a favor and send him to a shop that will cut Corian - it accepts paint and will last virtually forever! You don't want to cut it with your laser, a cnc router would make short work of those letters.


Hey guys,

I got a request to laser cut the word "JOY" with the nativity scene inside the O.
My table size is 600mm x 900mm, so I'm going to pretty much cut each letter to the max size I can.

The question I have is what is the best type of wood to laser cut that is easy enough to cut (not too thick) and easy to weatherproof, then paint red?

I know MDF is probably the worse of all options, but as it is quite cheap, is it possible to weatherproof it?

any advice or recommendations?

Thanks!

[Ross Moshinsky]

You can "weatherproof" MDF by using a shellac based primer and exterior grade paint. How long will it last? Hard to say. It should last at least one season and probably a couple more after that. Sooner, rather than later it will fail. Digging the letters into the ground like that will means moisture will get into the letters. If the letters were off the ground, they'd last a lot longer. I'd think 1/2" MDO where you cut it in 2-3 passes would be the best choice of a cheaper wood product. If you do a google search, you'll find many posts about how to seal MDO edges before priming and painting.

One other alternative is to cut a template out on your laser. Then go ahead and cut the letters out of 1/2" PVC from Home Depot. You can use a handheld router or a jig saw. It's more work obviously more work, but they will last a hell of a lot longer.

[Mohammed Issa]

Thank you very much for all your help. I think I like the coroplast idea. They're made to hold in the weather. I will ask the customer to make a simple 2x4 frame to hold up the letters.

Thanks again!

Mohammed