I am having problems sandblasting cedar sign blanks. For painting lettering, I used to be able to prime, coat out with 1 shot and apply stencil. Then after blasting I would stain, etc. Pull of stencil and sign would be completed. Now I prime with SW oil based primer, paint with 1shot and when I pull up stencil after blasting I pull up a lot of grain from the finished letters. Am I using too strong of sandblast stencil (high tack?) Please tutor me in the the proper technique, and proper stencil. Thank you very much.
Posted by Rick Sacks (Member # 379) on :
Sounds like you're using a mask for raw wood and possibly a flat grain board. I like blasting unpainted wood because it seems like I can blast deeper, and if there should be any small tearing it can be remedied with some filler without needing to go backwards. I like the Anchor 155
Posted by Vance Galliher (Member # 581) on :
jeff, why don't you go back to doing what you used to do ?
Posted by Glenn Taylor (Member # 162) on :
Jeff, just a couple things.
1) If you're pre-painting, I would use a medium tack mask.
2) For some reason, paint seems to cure a little slower than it used to. It could be my imagination but who knows. I would give the paint a couple extra days to dry before applying the mask.
Posted by Dave Sherby (Member # 698) on :
I just did 5 signs that way and it worked perfectly. The first thing you need to do is stop using SW primer. Get some First Step from Sign Life products. It is a bonding penetrating sealer that is a primer, but also penetrates into the wood to strength the wood fibers to reduce damage to the letters from sand bouncing back onto the edges. I even used the wrong mask and it worked fine. I didn't have any medium tack Anchor sandblast stencil since I hardly do any blasting since buying the CNC router. All I had on hand was some stencil that I had purchased years ago that was developed exclusively for blasting raw HDU so it is pretty high tack. By using First Step I believe that it really helped hold the grain together. Sign suppliers used to carry it but I don't know anyone that still does. The distributor runs a sign shop in Ohio and can be contacted here: http://www.tridicosigns.com/ Posted by Jeff Wisdom (Member # 6193) on :
ARRRGGGHHH
Okay I need some serious help (yes mentallay too) I used the first step and let it dry thoroughly. I then painted with one shot. and let it dry thoroughly. Then I applied the stencil anchor 117. Got it back from blasting and the paint, first step and grain lifted.
Please tell me what stencil to use. What primer sealer to use. What paint to use. What pressure of blasting. What material to blast.
Thanks in advance.
Posted by Chuck Peterson (Member # 70) on :
This may not be much help, but here is one tip I learned by experimenting that has worked well for me. After sanding the cedar down to 120 grit and blowing the dust off, I give it a coat of Zinsser Seal Coat, which is shellac. It seems to do the same thing as First Step but is faster drying and I always have some around. It soaks into the wood, so I don't see how it could peel. I use a foam brush for this step. It dries in a half an hour but I give it a few hours to be sure. Then I apply Anchor #116 stencil. I have my blasting done by an industrial sandblaster so I don't know what they use. I paint after removing the stencil. I've never had any luck putting stencil over paint. I don't do many sandblasted signs anymore but I have some done this way out there a few years now and they have held up well.
Posted by Dave Sherby (Member # 698) on :
Sorry I couldn't get back to you sooner Jeff, had some major medical issues to deal with. I preferred Anchor stencil. I never had a problem on redwood or cedar using Anchor 153 with my friction feed plotter. #157 has holes for tractor feed plotters. I never used anything else besides First Step so I can't comment on other primers. When I was sandblasting redwood I always used One Shot, but that was when it was still good paint. The pressure I used was always about 90 to 100 psi. I had a 1/4 inch boron tip and would keep the tip at least 2 to 3 feet from the sign. If the stencil starts turning brown you are dwelling too long and the heat will loosen the stencil and weaken the paint. I always used fine silica sand but there are safer alternatives available. I had a fresh air hood and am located outside the city on 20 acres.
Posted by Preston McCall (Member # 351) on :
Quarter-sawn redwood. Add some isocyanate hardener to the paint drying overnight and double coat it after a couple of hours. I have still have a big one looking good that I did in 1980! Used hardener and two coats of One Shot Lettering. Light tack on the mask for sure. High pressure blast, but stand back further.
Posted by Rick Sacks (Member # 379) on :
I suspect that the blasting is being done in as rapid a fashion possible. Holding nozzle too close for too long generated much heat and I think your problem lies there.
