What is "hot fuel proof" mean, anyways?

[Robert McHam]

Or better yet, what is "hot fuel"?

Does hot mean temperature or does it mean it still has the alcohol and nitromethane in it?

To some it means the exhaust residue which is hot in temperature but now lacks the alcohol and nitro it once had before it fired in the cylinder. To me this is no longer "fuel". So by using hot fuel proof should mean something else besides that it will withstand exhaust residue.

Raw fuel with alcohol and nitromethane is what I consider to be "hot" because the robust nature (technical jargon!) of these chemicals.

Some one set me straight please!

Please don't be shy!

Robert

[Bill Adair]

Hot fuel proof dope at one time (in the early days of glow engine powered models), probably meant it was resistant to any fuel with Nitro content. Many diesel and ignition engines of the day, used no Nitro at all.

Bill

[Ron Duly]

My experience has been that "cold fuel" (complete with alcohol) does the damage to dope. "Hot fuel" that has been thru the engine no longer has raw alcohol in it and the left over castor doesn't seem to bother the dope nearly as much (buty not nitrate).  I don't think the ads were referring to high-nitro fuels (which were certainly "hot").  What say you?

[Jim Kraft]

I remember using "fuel proofer" over my dope finishes back in the early 50's. If I remember right it was a Testors product. It was supposed to protect your dope finish from "hot fuel".

[Robert McHam]

Thanks for the info guys!

So far what I am hearing here pretty much stands in line with my way of thinking.

Only having one LHS to buy from (and it was kind of small) and being owned by a model enthusiast, a large variety of finishing materials was not to be had. Course he had Monokote but only carried two brands of dope. Pactra spray and Aerogloss for brush and airbrushing. Yes I remember the fuel proofer. It was Aerogloss but Testor's probably had   it too. Only bought it once and since the Aerogloss was already fuel proof I never bought any more of it. I also remember this fuel proofer was like water, not thick like dope.

The reason I ask the question is to find out what the problem is faced with other kinds of modern paint on models. Mainly the Rustoleum brand as many have said it works so well.
Some have talked about it being fuel proof and some saying that some colors do not do well, such as the metallics and the clear seems to be getting a bad rap as well.

Robert

[Ralph Wenzel (d)]

In general, the light colors of Rustoleum (White, Yellow, Cream, Red, etc.) tend to be fuel proof up to about 15% Nitro. This is true only if you wait at least 2 weeks before exposure to the nitrated fuels. Dark colors *Black, Green, Blue, etc.), Clear and Metallics are not fuel proof.

[50+AirYears]

I remember about 25 years ago, somebody told me Krylon was fuel proof.  since I wanted to paint a Sterling Corsair in the three shade scheme, I made up a number of frames covered with scraps of silkspan, silk, and Super coverite, and sprayed each with a couple coats of different Krylon colors that I intended to use.  After letting them a week or so, I poured some 15% Red Maxon them and let them set.  After a couple days, there wasn't a trace of softening.  So I painted the plane with Krylon.  However, on the first run of the engine, the paint turned into a messy goo.  It resisted the resh glow fuel, but couldn't stand up to the exhaust residue.  Took me longer to clean the goo off for repainting with Rustoleum than it did to paint it twice.

Luckily, I had about 8 coats of clear Aerogloss and a couple of their Balsa Fillercoat rfore the color finish.

[De Hill]

From what I remember, Hot Fuel was an alcohol based fuel burned in ignition engines. The hot fuel was supposed to heat the spark plug elctrodes so hot that they would ignite the fuel instead of the spark from the plug. Hot fuel came into use just prior to the developement of the glow plug.

Since Hot Fuel was alcohol based, it would soften Nitrate dope. Hot fuel proofers were made by several companies, and were a clear coat that was painted over the nitrate dope. Testor's and Aero Gloss were a couple of the manufacturers who made it.

[Steve Helmick]

I sometimes used (SIG, I think) "fuel proofer" over 3 or 4 coats of Nitrate or Low Shrink Butyrate on F1A stabalizers, because it made them glossy and very waterproof. Seemed kinda soft, like highly plasticized. Ya might look at the SIG catalog, anyway.  Steve

[minnesotamodeler]

In general, the light colors of Rustoleum (White, Yellow, Cream, Red, etc.) tend to be fuel proof up to about 15% Nitro. This is true only if you wait at least 2 weeks before exposure to the nitrated fuels. Dark colors *Black, Green, Blue, etc.), Clear and Metallics are not fuel proof.

I wouldn't go to quite that extreme, Ralph...the darker colors are a *little less* fuel proof than the lighter, but in my experience still acceptable everywhere but around the engine/fuel tank area! White certainly holds up best of all. Hence the white nose:

[George]

The first fuel proofer I used was by Comet. It was in a round jar, but not like the 4oz. dope jars.

Some things I remember discovering or reading:

Nitrate dope gasses off (dries) fast so you can paint over it within a short time.

Butyrate dope usually gasses off slowly. If you paint over it too soon, the gasses will form a layer that lifts succeeding coats IF the stuff over it gasses off faster. That's ONE of the reasons why you can usually apply butyrate over nitrate but not the other way around.

Nitro Methane is used to remove CA glue so make sure you paint-seal all CA joints in the engine compartment if you use it there.

Have not yet used Rustoleum or Krylon on models so can't address that.

George