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Jason Smalling
03-14-2008, 1:11 AM
Hello, I wanted to know if anyone knew if it is better to laser engrave wood before or after polyurethane top coat. I have done it before lasering, but if I travel to trade shows I wouldnt be able to. So I thought if I could clear coat everything and have them ready, when someone orders one, I could laser it and it would be ready to go. I tried one earlier with two top coats, but it gave a yellowish look to it, and the image didnt appear at angles. You had to look straight on at it to make it out. I thought maybe my power or speed settings were off, but before trying another one, I thought I would ask all the talented ones here to see if they know any inside tips. I appreciate any advice. Thanks!!

Darren Null
03-14-2008, 2:28 AM
Definitely before if you're going to colour fill, otherwise it's dealer's choice. Also, if you're having trouble drilling through poly top coat, there's a whole forum for 'finishing' on SMC to give you alternatives (Shellac, Danish oil and the like).

If you want it wood-coloured after your burn, run the job again with 100% speed, lightish power and this should clean up the charring. You may have to do this a couple of times. So. One heavyish burn to get through the poly, and one fast light pass to remove charring. Or you can reduce the power on your original settings and run the job a time or three, having much the same effect (once you get the settings right), but saving you having to mess with power settings between burns.

Rodne Gold
03-14-2008, 4:19 AM
Use paper based sign vinyl application atop the wood , then it doesnt matter what your finish is , the mask will protect the wood. Lots of power into wood , you want the "branded" look and a little depth , the only way to do that is to overburn - ie high dpi , high power , lowish speed.
Easy to apply the paper and remove if you at a show etc , You can even use a little shoe polish to darken the wood if the mask is still in place.
Even better is that you can do a test run , very high speed and very low power , for positioning as this will mark just the tape and not go thru it.
The paper is available at any sign shop , ask for low to medium tack application tape.

Joe Chritz
03-14-2008, 6:25 AM
Try a different finish and you will most likely find better results.

Try lacquer (HVLP or spray bomb) or shellac. Unless you are walking on the projects you don't need polyurethane.

Plus 8 minutes dry time is considerably nicer than a few hours.

Shellac is available in spray cans and it has the advantage of being dewaxed so you can always top coat later with anything you wanted.

Joe

James A. Wolfe
03-14-2008, 4:51 PM
I agree with Joe. I use spray lacquer in cans available at the local megamart. Dries fast, multiple sheen options and I use colored varieties for color fill when using low tack adhesive tape. If I'm not masking, the topcoat of clear seems to make any smoke residue easier to clean with an alcohol swab.

Jim