When to polish enamel paint

[Chevy II]

I painted my kit body 10 days ago with Testors little bottles. 50-50 mixture using lacquer thinner. Came out really nice, but I would like to polish it with some Novus #2 polish. 
How much longer should I wait, and how do I know when it’s ok to polish it?

[JollySipper]

When it doesn't smell like paint any more, it's pretty much cured......... The 'sniff' test!

[JollySipper]

You can also find an inconspicuous place that is painted and press your finger nail into it......... It shouldn't make a dent if it's cured..........

[LennyB]

I don't really spray enamel anymore but when I did I let it sit for a month.

[gman]

The paint being cut with lacquer thinner (which evaporates quicker than normal enamel airbrush thinner) should speed up the cure time compared to spraying with enamel thinner.

Enamel normally dries on the surface first, with lighter coats drying quicker than thicker coats. Polishing too soon will cut through that skin into layers that are still in the process of drying. As mentioned, if the surface feels dry to the touch and doesn't leave finger prints when you touch it, no longer smells like freshly sprayed enamel it may be OK to attempt some polishing.

Novus is pretty mild, so test by lightly polishing a small inconspicuous section to see how the paint reacts before going to town on the entire body. If it seems a lot of colour is coming off on your polishing cloth and the surface being polished is dull and sticky, stop until it has dried for a longer period.

[Mike 1017]

I agree the 50-50 mix helps with drying. Then into my dehydrator

Good luck

Mike

[carrucha]

I usually wait at least a couple of weeks.  I try to let it cure for a month to be on the safe side. In the meantime I work on subassemblies like the engine or interior.

[StevenGuthmiller]

On 11/10/2024 at 8:07 PM, LennyB said:

I don't really spray enamel anymore but when I did I let it sit for a month.

Same.

As. matter of fact, I usually let it sit for much longer.

Often several months.

One of the many reasons why I stopped using enamel.

 

 

 

Steve

[slusher]

Two week is all I waited with enamel rattle cans. It should be ready in 2 weeks..

[Bucky]

I always let enamel cure for at least two weeks. Lacquer, too, for that matter. I have used a dehydrator for enamel paint jobs, but left one in too long once and warped the body. One way you can keep from messing up a nice paint job is to paint a control piece along with the other parts at the same time. I would probably use a leftover part from the same kit. Then, when you think it's time for polishing, try it on the control piece first. If it doesn't take polishing well, then you'll know. 

[Nicholas]

i always use enamels,preferrinf MCW paints,and i always use their hardner mixed in with it,..with that said i always wait one week,sometimes longer if im doing other projects,and after a week you cant smell the strong lacquer thinner/enamel smell any more,then i wet sand/polish

[Muncie]

Long ago, I had a bad experience polishing Testors Model Master enamel with a very fine mild polish.  The paint ended up on the polishing cloth.  I fixed the damage to the paint and polished it with a cleaner wax.  It was much less aggressive and polished the enamel with good results.

[Bills72sj]

I also paint Testors enamels thinned with 50/50 lacquer thinner. I too wait 2 weeks. However, I never polish (Too gun shy)

[Bainford]

I usually leave enamels at least a month before cutting & polishing, all of that time spent in the dehydrator. Construction can happen slowly at my bench, so not uncommon to spend more time than that curing.

The issue with enamels, as mentioned somewhere above, is it forms a skin as it dries, and this skin inhibits the drying/curing of the paint underneath it. The heavier the coat, the worse the effect. As long as paint smell can be detected, the paint is still gassing out and uncured. I have found, though, that after a few days to a week of drying, the full cure can be sped up significantly by wet sanding the body with the first grit of the cutting process to remove the outer layer of the skin, then popping it back in the dehydrator for a few more days. The continued out-gassing occurs much more quickly then.

A few years ago I painted an MGB with Humbrol enamel thinned with lacquer thinner. The body had no fine detail, so I laid the paint on a little heavy to have plenty of material for cutting & polishing. After at least two weeks in the dehydrator, the body still had the faint scent of paint, so back into the dehydrator for five more days. After that, there was still a hint of paint smell, but with a deadline looming I decided to have a go at colour sanding. The colour sanding was going well, working my way through the starting grit, when suddenly I got a strong smell of fresh paint. Wiping the water off the finish, I found a dime-sized darker spot on the middle of the deck lid. Touching it lightly with a toothpick, the paint transferred easily to the wood. After nearly three weeks in the dehydrator, the paint under the skin was not only uncured, it was still wet. I continued to work the rest of the body just enough to remove the skin, then popped it back in the dehydrator. In two days the paint was solid and cured and exhibited no paint smell.

[Modelbuilder Mark]

On 11/13/2024 at 7:40 AM, Bainford said:

I usually leave enamels at least a month before cutting & polishing, all of that time spent in the dehydrator. Construction can happen slowly at my bench, so not uncommon to spend more time than that curing.

The issue with enamels, as mentioned somewhere above, is it forms a skin as it dries, and this skin inhibits the drying/curing of the paint underneath it. The heavier the coat, the worse the effect. As long as paint smell can be detected, the paint is still gassing out and uncured. I have found, though, that after a few days to a week of drying, the full cure can be sped up significantly by wet sanding the body with the first grit of the cutting process to remove the outer layer of the skin, then popping it back in the dehydrator for a few more days. The continued out-gassing occurs much more quickly then.

A few years ago I painted an MGB with Humbrol enamel thinned with lacquer thinner. The body had no fine detail, so I laid the paint on a little heavy to have plenty of material for cutting & polishing. After at least two weeks in the dehydrator, the body still had the faint scent of paint, so back into the dehydrator for five more days. After that, there was still a hint of paint smell, but with a deadline looming I decided to have a go at colour sanding. The colour sanding was going well, working my way through the starting grit, when suddenly I got a strong smell of fresh paint. Wiping the water off the finish, I found a dime-sized darker spot on the middle of the deck lid. Touching it lightly with a toothpick, the paint transferred easily to the wood. After nearly three weeks in the dehydrator, the paint under the skin was not only uncured, it was still wet. I continued to work the rest of the body just enough to remove the skin, then popped it back in the dehydrator. In two days the paint was solid and cured and exhibited no paint smell.

Have you worked with Enamel Hardeners from automotive paint supply houses? I picked some up, but have yet to try it. My hope is that between the hardener, and use of the dehydrator, it would assist in decreasing that timeline. I too build slowly so some paint has plenty of time to gas out. 

 

Edited December 23, 2024 by Modelbuilder Mark

[Bainford]

18 minutes ago, Modelbuilder Mark said:

Have you worked with Enamel Hardeners from automotive paint supply houses? I picked some up, but have yet to try it. My hope is that between the hardener, and use of the dehydrator, it would assist in decreasing that timeline. I too build slowly so some paint has plenty of time to gas out. 

 

I haven't tried hardeners, though as mentioned, time for enamels to gas-out is usually not an issue on my bench. Besides, most of my painting is now done in lacquer.

There are others on the forum that do use enamel hardeners with success. One of the hobby specialist paint shops (MCW?) market a hardener formulated for their enamel line.