• This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn more.
Pumpkin drop event

DTFB Spray Painting techniques

ofiesens2

Professional noob
#1
This is probably in the wrong category. Oh well. My apologies.

I have a plane designed by @RCSpaceFlight (can you tag people like on Twitter?) and I used it for my science fair project, which was: Which type of airfoil generates more lift: a KFm airfoil or a conventional airfoil? I ended up with comparable results, thanks to RCSF's plane and a couple rubber bands.

Ok onto my point. The theme for this year's science fair is "The Art of Science." For my piece of art I am going to spray paint a not-so-banged-up version of RCSF's plane in different colors (or as a 13 year old would say it, make it look cool). However, the paper on DollarTree foam board does not take spray paint very well. I was wondering if I could remove the paper and simply spray paint the foam. Has anyone else tried this? If so, does the paint quality come out fairly respectable? Any input whatsoever would be greatly appreciated.
 
Last edited:
#3
Looks like the right category to me :)

There are two kinds of spray paint on the market. The traditional kind has lots of acetone (and possibly some other nasty solvents) to ensure that the pigments don't clog the nozzle. Rust-oleum also has a new, low-VNC formulation called "ultra cover" that has much less acetone. Some of the other manufacturers probably do too.

Acetone dissolves extruded polystyrene very quickly. If you remove the paper from Adams foam board and spray some traditional spray paint on it, the paint will eat right through the foam in seconds. It's kind of entertaining to watch. Due to its lower solvent content, the "ultra cover" stuff only eats through the top millimeter or so, but it still damages the surface.

If you're going to use spray paint on foam, your best bet is to first brush on a very thin coat of oil-based paint, varnish, or primer. You can thin this wash coat with mineral spirits, which do not dissolve polystyrene. Here's a close-up of my FT3D, where I used Rust-Oleum gloss white, thinned with mineral spirits, as a first coat, then masked and sprayed with two kinds of spray paint. The blue paint is the "ultra cover" kind, and the black paint is traditional spray paint. Sorry about my poor masking skills.
IMG_1003.jpg

Lately I've taken to applying the spray paint with an artist's brush, so that I don't have to do as much masking. The overspray with the low-VOC stuff is particularly hard to remove.
 
#5
The problem with paint on foam board is that it will usually warp the board. If you don't care how much it warps but want it nice and black, then the cheapest thing to use is big bottles of poster paint. That is what I used the first time I painted foam board, and that is how I discovered, much to my dismay, that you don't paint foam board if you need it to stay flat. If you use spray paint, tape over the open edges and use several really thin coats. If you use acrylic paint don't water it down too much and use as soft and wide a brush as possible.
 
#6
The problem with paint on foam board is that it will usually warp the board. If you don't care how much it warps but want it nice and black, then the cheapest thing to use is big bottles of poster paint. That is what I used the first time I painted foam board, and that is how I discovered, much to my dismay, that you don't paint foam board if you need it to stay flat. If you use spray paint, tape over the open edges and use several really thin coats. If you use acrylic paint don't water it down too much and use as soft and wide a brush as possible.
I did a test with acrylic tube artist paint. It's a water based paint and will soak in to the paper and warp it all to hell. The light coat of brush on wipe off polyurethane that I use in the video has never caused any warping for my super cheap dollar store Adams readi board.

Your best bet is poly coat and then basic spray paint avoiding any exposed foam that hasn't been poly treated.