Anyone tried Shower Pan Liner for sandblast masking?

[Mayo]

I didn't want to buy a whole roll of sandblast masking for one wood sign, and I was thinking of using Oatey Shower Pan Liner instead. It's a 40mm PVC that feels like rubber or vinyl.

I'll have to come up with an adhesive that will hold the material in place and yet allow it to be removed when I'm done blasting. Possibly 3M Super 77 or the old stand by, Contact Cement.

I have applied sanding sealer to my Douglas Fir sign blank and I'm probably going to put primer over that if it will help the masking stick better.

I won't be painting the sign because the customer has to match some existing signs and they have their own painter in house.

I plan on trying the round over bit method of cutting the masking in place on the sign. This is my first attempt at it so my fingers are crossed...

[Mayo]

OK I tried it and it was a miserable failure.
The 3M Super 77 easily came off the PVC and remained on the Douglas Fir sign board. This allowed the masking to lift and get caught on my 1/16th inch bit while cutting the lettering.

Maybe with the correct adhesive this would still be an economical alternative to buying ready made sandblast mask. I had some contact adhesive but on a sample piece of wood, it didn't want to come off and I anticipated there would be problems removing the masking from the areas that would get blasted.

I should have bit the bullet and just bought a roll of sandblast masking however I don't do these kind of signs very often. Two years ago I threw out about half a roll that I had sitting around here for at least 7 years prior and the adhesive had dried up.

So I got some experience machining the wood grain from a photo, through Aspire. I was happy with the wood grain but not with the machining time of 8 hours 16 minutes.

Photos shown in the thread on How Fast Do You Cut in 3D.

[joe]

Mayo,

I'm glad to assist with your project but should tell you this a financial difficult project, no matter what.

First of, the choice of wood isn't very good. You need vertical grain to achieve the best look. But that as it is, forget the standard sb mask and 77 3m adhesive. That will get you in trouble.

Here's what I'd suggest. Route the panel using the standard profile and area clearance technique. Z down about.40" Then cut the letters from scraps of Dibond or PVC and pin nail them on. Then blast away. When finished remove the PVC or Dibond and fill the little holes. You can blast the devil of these materials and they won't wear out.

This technique seems to sell just as well as sandblasted. Looks good and money seems to flow in. I may make a sample showing this technique since it seems to be forgotten. Sandblasting by others is no problem when using this technique. You don't have to worry about the mask holding up or coming off.

[Mayo]

Thanks for the response Joe.
That's a good method to try on the next ones.
I may be doing two more of a different size. And I sure don't want to tie up the Shopbot for 16 hours to get them done.

The problem I had was with trying to cut the masking with the router while it was glued on the board with the Super 77. Even though the bit was only 1/16th, it still lifted the masking. If I had found the right glue or used real sandblast masking instead of shower pan liner, it probably would have worked fine.

I did get boards with as close to vertical grain as possible.
I just didn't pay attention to the one that was close to the center of the tree and it allowed the sign to warp after it was removed from my table.
I even flipped the boards specifically to avoid this, but stuff happens...

This working with wood is a lot different than working with EPS foam all the time!

[joe]

Mayo,

Even if you get the glue to attach perfectly, that's no guarantee it's not going to lift during the blasting process. The PSI shouldn't exceed 80 and the CFM should be at least 110.

Look, I'm telling you, this is the most checkered path you could take. How many hours do you expect to spend sanding, masking, blasting and fixing up the voids? Sixteen hours sounds like a bargain go me.

We used Hartco, high tack, and applied it to the complete panel. It must be rollered with a formica J roller. Then with a 1/8, needle, sharp "Brad Point" round over bit you score the surface of the mask. Not going all the way through.

Every batch of wood is different. Kiln dried is fairly predictable. Everything else is a **** shoot. And kiln dried wood is pricey. Good old "lumber grade" rough cedar makes me lots of money. I'm afraid the days of sandblasted signs are close to their end.

Joe