How to paint foam board

Ligbaer

50 Percenter
use krylon spray paint (colormaxx) instead of rustoleum the rustoleum peels the paper
acryllic works good for detail so do paint markers ,i dont have expeirence with paint markers but they were used in the p-40 video
my planes dont last long so i just use tape most of the time or just leave them plain
 

mastermalpass

Elite member
I use 6mm depron which has no paper covering. I've used various Plastikote spray paints, some colours will eat the foam if applied to heavily in one go.

I have found that accrylic paints brush on quite well without leaving brush strokes, but that does have a matt finish.
 

Robert S

Well-known member
My 2 cents:
- Krylon Colormaxx (paint +primer) works well in my experience.
- If using covered foamboard, rough it up with sand paper. You don't have to go crazy. Do it just enough so that its no longer glossy.
- Give it a first even and light coat and just walk away. Don't worry that its not prefect and that there are thin spots. Just walk away.
- Use consecutive even and light coats until it covers.
- Did I mention to just walk away after each coat?
 

Virtualjack

New member
To seal the foam, many use a clear polyurethane, the same sluff used for wood. This makes the foam water resistant and easier to paint.

Hold on just a moment - you paint on top of polyurethane and use the non-water poly? The non-water poly doesn't eat the foam?

Do you apply the paint onto the poly when the poly is tacky or do you let it thoroughly dry thoroughly and hit it with 220-300 grit sandpaper prior to paint application?

I ask because all of this seems counter-intuitive. From what I've read, only water based products are safe as non-water based contain solvents that eat foam. When I work with Wood, I never put the poly first. Depending on the wood or the finish, I might put on a sealer or primer but sealers and primers contain components that create adhesion with subsequent layers. For example, Gesso contains chalk.

---Jack
 

Merv

Site Moderator
Staff member
....The non-water poly doesn't eat the foam?...
The oil-based minwax poly, that I use, is foam safe. Not sure about other brands. I use the poly to fiberglass my planes. It's maybe 90% of the strength of proper epoxy resin. Good enough for me and much easier.
Be careful with the water-based stuff, if you put it on too thick, the water will lift the paper
Do you apply the paint onto the poly when the poly is tacky or do you let it thoroughly dry thoroughly and hit it with 220-300 grit sandpaper prior to paint application?
Let it dry completely
...From what I've read, only water based products are safe as non-water based contain solvents that eat foam....
That is true, solvents tend to eat foam. Not all non-water products contain solvents. Sometimes you can work around the solvent. With a rattle can, hold it 18 inches or so away from the foam. Hopefully the solvent will evaporate before the paint hits the foam.

ALWAYS try a new product on a scrap.

Here are a couple of articles that go into more detail.
Polyurethane treatment of dollar store foam core | Flite Test
Painting Foam Board | Flite Test
 
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checkerboardflyer

Well-known member
I just recently used Liquitex Acrylic paint in a bottle. Usually spray can paint gives a more even finish, but when it's cold out and spraying outside is not recommended, I can brush indoors with no odor. See some other trim and painting tips on my blog: https://foamboardflyers.com
 

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dap35

Elite member
I have switched to using Oracal 651 vinyl. Michael's (craft store) seems to keep it on sale for ~$6 for a 12"x60" roll.
 

Mr NCT

Site Moderator
I've finally found what works for me.
For brown FTFB - light sanding with 400 -600 grit and rattle cans. Binds well enough for fragile surface masking tape. Tried brush acrylic - too heavy; spray brush acrylic - orange peel finish.
For DTFB - minwax poly and let cure for a day. Without any other surface prep it seems to take anything. I found a cheap airbrush set at Harbor Freight for about $12. Walmart 50 cent acrylic cut 50% water works well. A sample size (about a pint) of paint at Lowes mixed to any color you want is about $5. I cut it 50% with water and the finish after 2 coats with 5 minutes between coats is beautiful.

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Mr NCT

Site Moderator
Follow up:
After letting the paint dry for an hour I tested it with fragile surface masking tape, regular blue tape and green frog clean edge tape. No paint came up with any of the masking tapes. It’s back to DTFB for my good builds and I’ll use the flight test brown stuff for prototypes and beaters.
 

Yankee2003

Well-known member
I've finally found what works for me.
For brown FTFB - light sanding with 400 -600 grit and rattle cans. Binds well enough for fragile surface masking tape. Tried brush acrylic - too heavy; spray brush acrylic - orange peel finish.
For DTFB - minwax poly and let cure for a day. Without any other surface prep it seems to take anything. I found a cheap airbrush set at Harbor Freight for about $12. Walmart 50 cent acrylic cut 50% water works well. A sample size (about a pint) of paint at Lowes mixed to any color you want is about $5. I cut it 50% with water and the finish after 2 coats with 5 minutes between coats is beautiful.

View attachment 226064 View attachment 226065 View attachment 226066

I too like to use an airbrush, though I am not good enough yet to spend a lot of money on airbrush paint.
Is the Lowes paint a certain brand? Is it also a water-based acrylic? Maybe obvious questions, but I don’t know much about paint yet.