Spraying Inside Cabinet Boxes

Spraying the inside of a closed box is challenging because of air turbulence and overspray. Here are some tips. November 9, 2008

When spraying, I have a real problem on the inside of the cabinet. No matter how I do it, I get a rough finish. It seems the turbulence is something I cannot master. What's the trick?

Forum Responses
(Finishing Forum)
From contributor R:
First off, a switch to pre-finished case material would be a big help. If you have to spray a large piece assembled, you need to use a retarder to slow down the drying so that the material can stay wet until you get the whole thing sprayed. A pressure feed sprayer would help as well. You need something that is going to move the material quickly.

From contributor M:
Contributor R hit it all right on. Switching to pre-finished material sounds like an expensive option, but remove the labor cost of spraying the interiors, sanding, spraying, sanding, etc. You'll quickly find it a lot cheaper.

Now, if that's a decision that's over your head (because you can't change it and your boss doesn't give a rip), then add some retarder.

If in a worst case scenario, you want it as perfect and smooth as possible and are having a bear of a time, I've done this with great success:
Load one cup/gun with your finish material.
Load the other cup with retarder/thinner mixed 50/50 (or straight retarder if you can move quickly).

Spray final coat of finish, immediately follow with the other gun with a mist coat of the retarder. Should keep things from getting too prickly.

You will not win any friends at the EPA doing this, not to mention that you are atomizing money right into the air, and I wouldn't make it a habit, but in a pinch, it works.

From contributor S:
Everybody is faced with this problem. Assuming that you don't have this problem on the outside of cabinets, that is, you are spraying effectively in general, the problem on the insides, for you and everybody else, is that you get a lot of blowback from your air stream when you spray inside, especially in corners. The general solution is to go to a wetter spray, that is, lower air pressure and more material volume going out relative to the outside. Lower air pressure will greatly reduce the spray bouncing off cabinet walls and landing on tacky surfaces.

Also, try to complete the spraying circuit around the adjacent surfaces of the cabinet interiors in a continuous path, so that you minimize the places where you are spraying up against surfaces you just sprayed, but that one of the surfaces has dried enough to not let the wet spray be absorbed into the coat. (You could basically call this "overspray" when it lands on the drier surface.)

You can also shield the places where you have to meet up with drier surfaces as you go along, but obviously you would have to work fast. Remember that spray "fallout" goes down with gravity. I used to spray all surfaces in a cabinet interior except the bottom. I would wait for the finished surfaces to dry, then sand all the overspray on the bottoms smooth, then spray the bottom surfaces separately. Now I just spray the cabinet parts the easy way: before assembling.

From contributor A:
I hate spraying boxes.

Get a good pressure feed gun and use a wide fan with a 1.2mm tip for nitro and a 1.4mm for cv or wb. Open it up to get a nice 10" fan and heave it on there quick like a bunny, 3-5 mils wet thickness. Shouldn't take more than 20-30 seconds to spray a 36h x 24w x 18d box on the inside. Sides first, then the top, then the back, and last the bottom. If you can lay the box back down on a lazy susan it's better, and you can do all sides, top and bottom, and then the back.

From contributor I:
Best solution is to leave the backs off the box until after finish.

From the original questioner:
Thanks for your responses. The cabinet in question is being sprayed with, now hold your breath, acrylic enamel! The GC gave it to me as it had to match the rest of the woodwork. Since I have one coat on, I think I will sand it and then break out my brush!

From contributor M:
I've sprayed it before. I'm assuming this is a waterbased acrylic, right? Perhaps coming behind the spray with a spraygun loaded with hot water (coffee-hot, not boiling hot) would lay down the overspray. If it's oilbased, come behind with mineral spirits. Either way, don't hose the water/spirits - just a misting.

From contributor R:
If we have cabinets that are matching a trim color, we have it color matched in a pigmented post cat lacquer. If the GC insists on paint, we will deliver and install primed and his painter can paint it.

From contributor A:
Best option, pre-finish parts before assembly. Leave the back off. Spray the cabinet upside down so all of the over spray settles on the top panel, which no one will touch or see.

From contributor P:
I have the same problem. I spray the insides, then the outsides, and some overspray from the exterior spraying falls into the box. I have the backs in (unless it's a stained interior, then the backs are left off). Since a job could be 10, 15, 20 boxes I don't like to piddle around. When the cabinets leave the finish room to assembly, I have a helper "magic paper" the interiors and wipe them down. Magic paper is worn down 280 sandpaper. Baby butt smooth.

From contributor T:
An air assisted airless setup helps a lot. Much less blowback than any kind of compressor or turbine-driven gun.