Topic: Baking Dupli Color

[rocco]

Hello all,

Quick question about baking Dupli-Color, the can says to do it at 300F for 2 hours, however, I've read through every other thread on this site and no one does that hot for that long. Should I consider doing it shorter and colder?

Thanks,

Reilly

[Powderman]

150-200 for an hour should be plenty. If doing in a oven I leave the heat on but the door cracked so it isn't contained.

[rocco]

Thanks,

I'll be doing it in a "hot box" in the garage. With a hairdryer I guess. I think my heat gun is too hot, puts out 480F on the lowest setting...

[rocco]

Maybe a stupid question but...

I was baking the parts in a box. When it was done, I picked up the box to move it into my house to cool so they wouldn't go below 60F, one of them fell over, the oil pan, and bumped up against the head. Not hard or anything. Put the paint came off real easy. Now I know they were still really hot. So part of me is saying, well, the paint is soft because it's hot. The other half of me is saying, the engine is going to get hot a lot. Is it just this first curing time that the paint can't be touched until it cools?

[Jerry Rxman Griffin aka MuthaF'er]

What's wrong with your controlled temperature oven with the timer?

[Jore]

I've been using my gas kitchen oven with no problem whatsoever, I just got a large faced thermometer to monitor it doesn't get to hot or too cold. If you wait a week between painting and baking it hardly smells, it also helps if you dry parts in the sun for a couple of days prior to baking.

After baking the paint is usually really though and doesn't scratch or peel if you run your fingernail over it. So far the only problem I had was with some paint curling, but that was do to the layer being too thick and just waiting a day to bake after painting.

[calj737]

did the paint "chip" or "peel" off as a result of the collision? If it chipped, its cured. If it "peeled", you've got an adhesion problem (again). Picture please?

[flybox1]

Its all in the prep.
30 min @ 250F was a I did.  All items have held up well.

[przjohn]

Did you use a primer before applying the heat resistant paint? If so, was the primer rated for heat resistant? If the primer was not rated for heat resistance then maybe that is your problem. I have never primered an engine and just used VHT directly to the clean surface and cured as directed, never had a problem.

[rocco]

The paint came off as irregular chips. Not a peeling pattern. I could drag my nails across it with no issue today.

[calj737]

I think you'll be fine.

When you use heat to cure paint, its important to not use too high a temperature as it "flashes" the exterior of the paint, curing it prematurely on the surface. Paint wants to cure inside/out. Think of "searing" a steak. Charred on the outside, rare on the interior. Lower temps, longer heating allows the paint a proper cure process. 150-250* is plenty high enough, and let it cure for 1-2 hours maximum.

Any hotter and you'll end up shrinking the paint and getting a hard surface and soft interior. Who knew there was that much to painting an engine, for Pete's sake! 

[rocco]

Haha, definitely not what I had expected. From initial degreasing  to cleaning to re-painting, it's probably the longest part of my build!

Once again, thanks for the info!

[SOHC4 Cafe Racer Fan]

You can also do the hot box method and run it through 2 heat cycles to help it cure.  Most likely, the outside was firm but the paint underneath was still uncured.  Since you are not using an actual oven, I would err on cooking it longer.