Spraying a Big, Heavy, Complicated Piece
Finishers consider ways to approach spraying a complicated job. May 15, 2008
Question
This is an alter I built. It is now stained, shot with VS, and sanded. I'm going to use MLC dull nitro. The problem is everything, inside and outside, is very visible and needs to be finished. My first idea was to finish the interior, then mask it off and do the outside. But the edges of the arches are radiused, so there's no good place to have tape! I can't imagine using enough retarder to keep the entire thing wet long enough to avoid the dusting. Any ideas?
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Forum Responses
(Finishing Forum)
From contributor R:
We have had more than one person spraying on a project for this reason. It gets interesting as you fog each other in the face, but with some coordination it can work.
From contributor C:
What spray system are you using? That will help me tell you how I would spray it.
From contributor T:
I would have pre-finished the parts and assembled it as the last step. This is also a much faster way to build. Just pre-assemble everything to make sure it all fits, then label all the parts so it all goes back the same way. Use screws, pocket holes, air nails, dowels, glue... whatever it takes.
From contributor D:
It can be a challenge when dealing with these items, and in my early days I would have had to really think this through, but I can not imagine this piece requiring more than 6-8 minutes tops to coat completely inside and out (unless the perspective I am seeing is really skewed and it is actually 10' tall). Calculate your coating and retarder evaporative rate to exceed that timeframe by a minute or two, then set it up on a turntable or cart. Set it up in front of the booth so that the outside face is facing the booth but at an angle so the air flow is driven toward a side opening. Begin spraying the inside of the face first and continue around the inside till complete, then quickly turn the piece/cart so that the outside faces are facing the booth at an angle (if you are doing the back also) and continue.
If you plan this in your head and move it at a good calculated speed including the movement of the cart, you should be able to get all the way through with all overspray always drawn away from the piece. Does it make sense the way I tried to relay it?
From contributor E:
Add some butyl cellosolve to the topcoat to slow down the flashing, and work from the inside out and side-back-side-front, in that order. Fix any overspray with the backside of a piece of sandpaper after it's cured.
From contributor J:
With enough retarder I don't see a problem. But I tend to use way more than recommended, to the point I just fog the finish on and it melts all over. It always comes out glossy that way, though.
From the original questioner:
That's pretty much what we came up with last night. Leaving it on the bench, rotating the bench with a pallet jack, and then walking boards to get to the top. No, it's not 10' tall, but she does weigh a little over 1100lbs.
From contributor A:
Since you are going for the most forgiving finish, dull, why spray it at all? That fine piece of work is begging for tung oil or any other high quality hand applied finish. The gel poly will build decent coats. This project looks like a nightmare to spray. I'm not sure what advantage dull nitro would give you on this project. If anything, it dries so fast that you will get overspray all over it. If you want to spray, I would use a dull marine varnish that takes 24 hours to dry. It will not overspray and takes hours to skin. It's also more durable than nitro.
From the original questioner:
Didn't do the alter today, but did shoot the gift table, lectern stand, and the ambo. The ambo was kind of a test for the mix and method. It's kind of the same design, only smaller. It worked perfect! Had plenty of wet time quite a while after it was finished -should work on the alter. Thanks!
From contributor Z:
I don't see any problem whatsoever. The problem might be your spray equipment. With a Kremlin, cat tech or one of these air assisted units, this is a piece of cake. You can spray upside down with very little overspray. Tung oil would be nice, but you need to make money.
From the original questioner:
Shot her today, and turned out perfect. I think I was too nervous to "just do it." Thanks to everyone for the advice.
