[Richard Lee]

I have recently completed painting a Great Planes 1/5th scale Piper Cub with latex paint over Solartex. I'll be flying with a four stroke glow engine. I searched the Internet for tips to fuel-proof the latex paint and found all kinds of conflicting information. There is no argument that epoxy is a good fuel proofer, but I am just not comfortable putting epoxy into my $300 spray gun. So I went searching for an alternative. The only way I could feel confident applying a fuel-proof clear coat over my plane was to do some tests myself.

After four weeks of spraying, dry time and testing, here is what I found:

Let's fast forward to the conclusion: The best clear coat is Varathane Professional Crystal Clear Finish, in a black rattle can. This is the only finish that showed absolutely no adverse effects to glow fuel.

For my experiment, I tested several clear coats, most available at Home Depot or Canadian Tire. All were satin finish. All the clear coats were sprayed over the same latex paint I used on my plane - Valspar Duramax exterior satin paint. I used a bright yellow as the base colour and a rusty orange for accents. Each clear coat was sprayed on with 3 coats, then the clear coats dried for a week under a heat lamp. Each clear coat was tested by putting some puddles of fuel on the finish and letting it sit for about 20 minutes. I tested all finishes with 10% nitro and 15% nitro.

The finishes I tested and the results are as follows:

Varathane Professional Crystal Clear Finish in a black rattle can. This poly darkened the paint colours slightly, but not enough to be concerned. It sprayed on nice and no lap marks were visible. I let both 10% and 15% nitro fuels sit on this finish for 20 minutes and then wiped it off. There was no sign of where the fuel had been. The poly was perfect. So, it appears this finish is certainly fuel proof. I found the satin gloss of this finish to be shinier than most other satin finishes tested. I have now sprayed my plane with this finish but may try dulling the satin gloss with fine steel wool later on.

Minwax Fast Drying Polyurethane in a black and gold rattle can. I had hoped this would be the winner. It sprayed so very nicely - the final finish was spectacular. This poly also has the least gloss of all the satin finishes tested. It provided a very nice matte finish. 10% nitro fuel did not burn through the finish, but it did leave a noticeable dull circle where the fuel had sat. 15% nitro left a more noticeable dull spot where the fuel had sat, but again the fuel did not burn through the poly and reach the latex paint below.

Rustoleum Painters Touch Clear Matte in a white rattle can. Most clear finishes I tested darken the colours a bit. This Rustoleum finish lightened the colours significantly. It took my super bright yellow and turned it into a soft pastel yellow. Fuel performance was similar to the Minwax. 10% nitro fuel did not burn through the finish, but it did leave a noticeable dull circle. 15% nitro left a more noticeable dull spot where the fuel had sat.

Varathane Professional Crystal Clear Finish in a quart can. I tested this since rattle cans can get expensive at about $10 each, so why not use my sprayer and use the poly in a quart can? The finish from the quart can had much more amber colour than supposably the same finish in a rattle can. The paint colours darkened considerable and my bright yellow became a dark yellow. This satin finish, in the quart can, also had a higher gloss level than the Varathane in the rattle can. Was it fuel proof? Absolutely. I'd say this finish is ideal for brush-on applications where looks don't matter - areas like the inside of a fuselage.

Varathane Cristal Clear water based finish in a quart can: A number of forums I read said water based floor finishes are fuel proof. So I tried two finishes. This finish had a very nice soft satin gloss and did not change the colour of the paint at all. That's the good news. 10% nitro left a noticeable dull circle in the finish and 15% nitro burned through and removed the paint.

Varathane Nano Defense Clear Satin Floor Finish - Being a floor finish, I figured it might be more durable than the other water based Varathane I tested. It actually performed fairly well. I left 15% nitro fuel on the finish for about 20 minutes then wiped it off. There was a dull spot where the fuel had been but I had to hold my test piece up to the light and tilt it this way and that way to see the spot. I'd say it is almost fuel proof. Perhaps if my test sample had dried for more than a week, maybe it would have performed even better. This finish did darken the paint colour a bit and was a bit glossier than most other finishes.

Lacquer: I am a cabinet maker so I have gallons of good 'ol satin lacquer. This is the real lacquer that gets you higher than a kite when spraying. (I love my job!) I knew what kind of finish I'd get even before spraying - a very nice matte finish with no change of colour to the paint below. But was it fuel proof? No way. Both 10% and 15% fuel burned right through and took out the paint.

I have read that acrylic lacquer is fuel proof but I did not test this. My lacquer supplier only sells acrylic lacquer in gallons and I was not going to buy a gallon for my tests. However, I do want to try the acrylic lacquer for cabinet work, to be more environmentally friendly. When I do get a gallon, I will test it with fuel and will report the results.

I read in a forum that there is a PlastiKote Acrylic Lacquer clear coat in a rattle can that is fuel proof. However, there was no such clear coat at Benson Auto Parts, who sell PlastiKote. Can anyone report on the effectiveness of PlastiKote?

So forget all the forums and chat rooms about this finish or that finish. Go with Varathane Professional Crystal Clear Finish in a rattle can, or...... load quick dry epoxy into your expensive spray gun.