Paint Wear on Corners & Edges of N Scale Models After Handling

[MK]

Looking at it from a different angle, could it be surface tension combined with geometry?  I know the type of paint and prep has a lot to do with it and I'll let the experts (above) address that.

In any "sharp" surface that is 90 degrees or more like an edge, if there is any surface tension at play, the edges will get less paint.  Think of a drop of water on a surface that beads up.  The perimeter will certainly have less water as it rounds off to meet the surface.  Could this effect possibly be at play on edges?  Paint can't certainly be the same thickness when wet at the edges else it will roll off.

I have no idea how to solve it other than that hit the sharp surfaces a few more times with the airbrush, but not so much to cause drips and buildups, the inverse problem that can happen on edges.

[tehachapifan]

I had a lot of problems with paint coming off on the corners/edges in the past. I mostly used modelflex, but have a strong suspicion that the problem was due to spraying dullcote (from spray cans) on top. Since moving to Japan (and having to deal with the completely different set of paints available locally), I've been using tamiya paints (both the spray cans, which are "smelly", and the jars, which are more or less water-based) as the paint, and Mr Topcoat (flat, semi-gloss, gloss) as a top coat after applying decals. This seems to result in a much more stable paint job (no problems so far with anything I've done in the last several years). Mr Topcoat is water base, while dullcote is not. This makes me think that the solvent in the dullcote was destabilizing the paint that it was sprayed over.

Interesting findings! I used to use dullcote in my earlier enamel days when I was in HO (with good results) but I've only used water-based gloss, semi-gloss/satin and dull finishes since my switch to N scale and to water-based paints. The reason for the switch to the water-based finishes at the time was I wanted to be able to control the application with an airbrush versus a rattle-can.

Looking at it from a different angle, could it be surface tension combined with geometry?  I know the type of paint and prep has a lot to do with it and I'll let the experts (above) address that.

In any "sharp" surface that is 90 degrees or more like an edge, if there is any surface tension at play, the edges will get less paint.  Think of a drop of water on a surface that beads up.  The perimeter will certainly have less water as it rounds off to meet the surface.  Could this effect possibly be at play on edges?  Paint can't certainly be the same thickness when wet at the edges else it will roll off.

I have no idea how to solve it other than that hit the sharp surfaces a few more times with the airbrush, but not so much to cause drips and buildups, the inverse problem that can happen on edges.

I actually sort of wondered this too at some point. I notice that some water-based paints kind of bead up in droplets on the smother bare plastic surfaces with the first pass or two with the airbrush, perhaps due to water tension(?). My understanding is this initial beading is normal and to be expected and they do normally flatten-out nicely, if you leave them alone and let them dry thoroughly. I've also noticed that, if you apply the first pass a little to heavy and get a larger bead/droplet, that one might dry with a little more paint piled up in that spot, which is still ever-so slight once dry. Subsequent coats then seem to go on much more evenly with each pass. Perhaps this initial beading might be something that a surface primer might help with(?). I sort of have some vague recall from researching this before of someone adding something to the paint mix to break the surface tension, but I really didn't want to mess with that.

[Santa Fe Guy]

Thanks, Rod! Are you using an airbrush version of the Tamiya primer?
Hi Russ.
I have mostly used the pressure pack to undercoat when painting larger models like my military stuff. I find that the light grey of the Tamiya allows for a good top coat colour without trying to apply too much top coat. Its such a while since I did any N Scale loco painting I cannot recall what I used in my airbrush just know it was grey and probably Tamiya as it goes on so well. Make sure you use the Tamiya thinners Russ and clean your air brush with the cheaper stuff.
Vallejo make a good range of undercoats also.
Have fun.
Rod.

Thanks, coosvalley! Good info.

[mark.hinds]

FWIW, I have the same issue with brush-painted Vallejo acrylics on military miniatures.  It is my impression that the paint takes many days (a week?) to fully cure / harden, as opposed to merely setting.  Until this occurs, I have to be very careful how I handle them, and occasionally touch up the edges.  I paint under magnification BTW. 

MH

[tehachapifan]

Thanks for the info and tips, Rod and Mark!