How to prevent underside of projects from being marred while spraying

[Alan Lightstone]

OK. This problem chronically drives me nuts.

I've tried many ways to support boards, furniture, etc... while spraying in my spray booth. All have proved to have disadvantages so the bottom of the object always is marred in one way or another. I usually spray Pre-Cat Lacquer, but have had the issue with other finishes.

1.) Painters Pyramids - I took some of these, weighted them down with buckshot/epoxy in the middle, and put sandpaper on the bottom of those, so they don't move. But invariably they make scratch marks on the bottom surface.

2.) Rockler Bench Cookies - Great to keep pieces from moving, but the rubber surface always leaves a round mark on the surface. I've seen it react to lacquer, and especially with varnish.

3.) Blocks of wood (seems the best, but invariably there are rectangular areas where overspray lands around them leaving rectangular marks).

4.) Lazy susan with paper towel on the top of it (seems in ways the best - certainly helps spraying), but also the issue with square marks from overspray, plus I have had the paper towel stick to a few of the surfaces.

5.) Rubber sanding mats - The worst. Totally keeps the project from moving, but totally sticks to the wood underneath at worst, and leaves a significant pattern at best.

So what do people use that actually works? I just haven't found it. I can spray a beautiful finish, but the bottom is always an issue.

[Jamie Buxton]

Taller supports. Overspray getting up underneath a part comes from air flow bouncing off the floor of your booth. Instead, if the floor is a couple feet away, the overspray just falls to the floor.

[Mike Henderson]

When all else fails, I mask off the back.

Mike

[Gustav Gabor]

These simple supports have served me well for the last 20 years or so....



Just a piece of plywood with 3" screws sticking through. ( 5" - 6" would be even better) Sanded the sharp points of the screws off a bit.
I find the supports work much better when on top of those stain cans, gaining more height below the work piece, as Jamie pointed out.
10" or more works well for me.

These can be made in any size to accommodate various panel sizes.

I get very, very little overspray on the bottom of the panels as long as the spray gun isn't held at 90 degrees to the edge of the panel when spraying the edges.
I point the gun down slightly beyond 90 degrees (maybe 10 - 15 degrees towards the floor)
The edge still gets excellent coverage, and minimal overspray on the bottom.

This of course only works spraying one side at a time, always doing the back side first. I let the panel dry about at least an hour on a drying rack, then spray the good side last.
I do this for sealer and top coats.

[John TenEyck]

I use the painting pyramids most of the time. I set them on a panel that is smaller than my workpiece so that the overspray doesn't rebound back up to the underside of the piece. The problem with painting pyramids is they can easily dent the workpiece; not a big deal on the back of the panel but it sure is on show side. So when I spray the back side of panels I usually sit them on a large piece of wood with a paper towel for cushioning. Never had a problem with the finishes I use, even BM Advance which cures according to the calendar.

And there are some cases where you just have to mask off the back, as Mike said. There's no universal truth, like most things.

John