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I have been scratch-building some shields and made the bad decision to use some low quality acrylic paint. This has led to the shields having thick paints in some areas and no (noticeable paint) in others. I am wondering what I should do now? I am not overly keen on stripping the paint due to concerns that it will have on the glue used for the modelling. Should I just try to sand it back a bit? Alternatively if I paint on top with a better quality paint will it sort itself out (in that it will naturally disperse more paint into the recesses and so with several layers it will be less noticeable)?

Sanding will cause more problems, potentially. If the paint is too soft to sand, it will tear slightly, making a seam in the paint which will be worse. Going over it probably won't help either.

You could try to spot strip the paint off the front of the shields which may (you tell me) not affect the glue - put iso/Dettol on a paper tower, press it to the front of the shield, put it in a plastic bag. It may just wipe off after a few hours.

Sanding it is tricky. You need to make sure it's 100% dry (and I mean cured through and through), or it will make a mess.

Then, you need ultra fine grit sandpaper -- 4000+ grit stuff, preferably on a foam pad or block. The one I have doesn't even feel like sandpaper -- it feels like foam block with a piece of actual, regular paper on it (it's 12,000 grit). I also have sandpaper going up to 12,000 grit, but it's harder to use than the foam block. Then you slowly, slowly, work away at it, a tiny bit at a time. It takes a long time. Then, you need to cover the area with another coat of very thin paint, and then refinish it the way you want.

I've done it before, but really only on models that already had a huge time investment in them.

Generally, I would say it's not worth the effort; it's easier to snap the piece off (or cut it off if you have to), strip it, repaint it, and glue it back on. But if you are interested, these are the products:

The finishing sandpaper -- http://www.alphaabrasives.com/alpha/sanding-film-products.php
Scroll to the bottom of -- http://www.alphaabrasives.com/alpha/sanding-files.php

 Talys wrote:
Sanding it is tricky. You need to make sure it's 100% dry (and I mean cured through and through), or it will make a mess.

Then, you need ultra fine grit sandpaper -- 4000+ grit stuff, preferably on a foam pad or block. The one I have doesn't even feel like sandpaper -- it feels like foam block with a piece of actual, regular paper on it (it's 12,000 grit). I also have sandpaper going up to 12,000 grit, but it's harder to use than the foam block. Then you slowly, slowly, work away at it, a tiny bit at a time. It takes a long time. Then, you need to cover the area with another coat of very thin paint, and then refinish it the way you want.

I've done it before, but really only on models that already had a huge time investment in them.

Generally, I would say it's not worth the effort; it's easier to snap the piece off (or cut it off if you have to), strip it, repaint it, and glue it back on. But if you are interested, these are the products:

The finishing sandpaper -- http://www.alphaabrasives.com/alpha/sanding-film-products.php
Scroll to the bottom of -- http://www.alphaabrasives.com/alpha/sanding-files.php

Why so fine? I never go that fine unless I'm going for some sort of polished finish (like on a clear canopy or something). I wet sand stuff back with 1200 or 2000 grit then apply a light coat of varnish or another thin layer of the base paint and you can't tell the area was sanded. I might go to 3000 grit if I'm concerned the finish isn't good enough. Just regular old sand paper bought from an auto parts store, look in the painting section. I may mount it to a block or stiff foam if I can be bothered or if it's a very large surface.

But not all paints are sandable, some are too rubbery and will just come off in chunks, I've sanded VMC after letting it dry for a few days and it came out fine, I'm not sure all acrylics will behave the same though. Vallejo's polyurethane primer doesn't sand very well, if at all.

You could try stripping it locally as well. Apply 100% isopropyl alcohol to the area, you could use a small stiff brush of some sort, maybe a tooth brush, it'll slowly soften it and remove it.

I had a similar problem on a stormtalon gunship canopy. I used a paint brush and dettol - had to be patient, but it worked eventually. I'd suggest a paint brush or q-tip. Depending on the angle, you could soften it up with the dettol and then try gently scraping the paint off.

AllSeeingSkink wrote:
Why so fine? I never go that fine unless I'm going for some sort of polished finish (like on a clear canopy or something). I wet sand stuff back with 1200 or 2000 grit then apply a light coat of varnish or another thin layer of the base paint and you can't tell the area was sanded. I might go to 3000 grit if I'm concerned the finish isn't good enough. Just regular old sand paper bought from an auto parts store, look in the painting section. I may mount it to a block or stiff foam if I can be bothered or if it's a very large surface.

But not all paints are sandable, some are too rubbery and will just come off in chunks, I've sanded VMC after letting it dry for a few days and it came out fine, I'm not sure all acrylics will behave the same though. Vallejo's polyurethane primer doesn't sand very well, if at all.

You could try stripping it locally as well. Apply 100% isopropyl alcohol to the area, you could use a small stiff brush of some sort, maybe a tooth brush, it'll slowly soften it and remove it.

Mostly it was the options available at the hobby shop. There were a zillion options up to about 1000 grit, and then it was big jumps to 8000 and 12000. I do have some 4k and 8k, but it' paper, and I prefer blocks.

You're totally right about sanding rubbery paints. You can tell these apart on GW paints, too, when you clean the lids. On the other hand, the rubbery paints usually aren't bad brushstroke offenders -- it's always the chalky ones that are hard to deal with.

Like I said, though, it's so rare that I do this at all.

 Talys wrote:
Mostly it was the options available at the hobby shop. There were a zillion options up to about 1000 grit, and then it was big jumps to 8000 and 12000. I do have some 4k and 8k, but it' paper, and I prefer blocks.

The reason for the jump is probably because the rough papers are for model preparation (filling seams and sanding them back) but those really fine papers are meant for polishing parts to a high gloss finish.

I don't have any 1000, but I know if you wet sand something with 2000 you won't see the scratches once you put another layer of paint or varnish. Probably even 1200 would be fine but I don't usually use 1200 because it removes the paint too quickly and in the past I've accidentally sanded through too many paint layers and had to respray the whole thing

The 8000+ stuff is meant for things like car models or pre-decaling, where you want a really glossy finish. Unless you are a god of spraying your gloss coat will either have a slight grain to it or a slight orange peel (and even if you are a god of spraying you are probably such a perfectionist it won't look good enough anyway ). If you want a top notch finish you have to sand those back then swap to a polishing compound to get a really shiny smooth finish. The same applies to canopies if they're scratched up and you want to bring them back to a good finish.

In that case your sanded/polished finish is the final layer which is being displayed, so has to be flawless. For what the OP wants, as long as he's happy enough to put another layer of paint on after sanding, I'd say buy a couple of sheets in the 1000-2000 range and you should be fine. That range of grits is very common in automotive painting so you'll find them in auto parts stores.