werdy666

I understand that people here say it can take months for enamel paint to dry, but what can speed up the process? heat? wind?? lol

I airbrushed the enamel paint but thinned it with lacquer thinner, hoping it would take less time to dry! and also the fact that i will probably spray lacquer clear over the top.

one thing i did find strange is that i have sprayed gloss enamel black as undercoat for alcad2 paint with only a day difference between paints. and never had a problem with paint cracking or doing anything bad.

Thanks

Werdy666

ZoomZoomMX-5

Thin with lacquer thinner and use a food dehydrator.

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ariel

On the clear i wouldn't spray laquer clear i would use an enamel or urethane clear. If you spray laquer you maybe asking for trouble. Alclad II is sprayed very lightly and a thin coat most likely the chemicals in the AlcladII are not as strong as clear Laquer.

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cyberkid

Enamel... heat in a dehydrator of some sort. Try to avoid wind though, as enamel drys so slowly, the wind will blow dust etc ruining your paintjob.

Be carefull on spraying lacquer on enamel, its pure luck. Technically, it shouldn't be done.

The reason that you can spray the lacquers from the alclad line on enamel is because they are pretty weak. Their chrome color specifically needs to be sprayed on enamel to grip better.

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ZoomZoomMX-5

I missed the "lacquer clear" over enamel.

Don't do it if it's automotive clear! It will ruin the enamel.

Be very careful if using Tamiya or Testors lacquer clear. The Testors shouldn't be a problem, I've used it over Testors enamels that were mixed w/lacquer thinner. Airbrush the clear in thin layers. And test the combination first, use white plastic spoons to check for compatibility.

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MPWR

Technically speaking, enamel doesn't dry, it cures. It's a fundamentally different process.

Paints like nitrocellulose lacquers (like automotive lacquers) and aqueous acrylics truly do dry. The binder of these paints is dissolved into solvent (either lacquer thinner or water), and the paint hardens as the solvent evaporates.

Dehydrators can be very effective in driving off solvents- they're obviously designed to evaporate water out of food, and evaporating solvents is very similar.

Enamels harden due to oxidative crosslinking. When enamel is exposed to oxygen, it starts a chemical process which molecularly hardens the binder- creating a sort of 'shell' as binder molecules link with each other. Heat and convention have a limited effect in speeding this process. I may increase the crosslinking process slightly, but certainly not in the way that it dries solvent.

If you thin enamels with lacquer thinner, you're not changing the curing time. By introducing a volatile solvent, you're creating a mix that needs to cure and dry. But after the solvent has finished evaporating, the enamel binder still must cure- and the binder will still cure at it's own pace.

If you want enamel to cure quickly, the best way is to spray it as thin as possible. This way as much of the paint as possible is exposed to oxygen, and it can all go to work on curing. If you apply enamels thickly, only the outside surface is exposed to oxygen, which can dramatically increase the curing time of the paint deeper in the layer. Spray enamel too thick and it is possible to keep some of the paint from ever completely curing. The outermost portion exposed to air can cure perfectly well- but this cured outer portion becomes a barrier to prevent the paint deeper in the layer from being exposed to oxygen. As a result the paint will always be soft, under a thin cured film.

This is why enamels have such strange application instructions- you must spray everything on at once (within a couple of hours), or you must wait days or weeks to apply another layer. If a layer is applied and it begins (but does not complete) curing, only to be covered by another layer, the first layer will never cure.

Of course applying many thin fully cured layers is a perfectly acceptable (if very time consuming!) way of applying enamels. But if you try sanding/polishing it, you will see quickly that each of these individually cured layers is distinct. You will clearly see where you've sanded through one to the layer below, rather like sanding through an onion. It makes enamels difficult to apply thickly....

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wouter1981

Well i completely agree with MPWR. Speeding up enamels is possible with extra heat, because the drying of enamels is a chemical reaction and almost every chemical reaction goes faster with higher temperatures but thin coats is defenatly the way to go. When you spray enamels verry thick there is indeed a chance the paint will never dry. I tried it once when i was experimenting with giving an diecast a new colour. Primed, enamel colour and a VERRY thick enamel clearcoat. I put the diecast for 4 months to dry above a heating element. I couldn't smell any paint, tryed to polish and it just became hazy. A sign you're paint isn't dry enough.

My first cars were painted with enamels, with satisfying results. But they were almost un-polishable. So i started to use acrylics and lacqeurs. But lately i use enamels again, but only for a clearcoat. It's not volatile, so you can spray it over every kind of paint i've ever used. The trick is to spray verry thin and verry diluted coats over a perfectly even sanded colour. You can easily have a verry glossy surface that needs minimum of polishing, but you will need to be patience and wait a lot of time until you start polishing. But hey, that's the ideal time to buy a new model ;-)

And indeed, spraying lacquer clear over a enamel base is a verry bad idee. If you're planning on using enamels for a colour, use enamels for a clear. And don't use humbrol clear. Most humbrol clears i've ever bought are already yellow in the bottle. Revell is a much better option.

Didymus

Thanks for an incredibly informative post, MPWR. Now we know why enamel is such a PITA.

It's posts like this that make this forum truly worthwhile.

Ddms