How fine? [sandpaper]

[GazzaS]

Hi friends,
I am curious as to how finely grained sandpaper will be required to avoid showing marks if the styrene surface is to be airbrushed.

Thanks for reading!

Gary

[biggles2]

A graded set like this http://www.micromark.com/micro-mesh-fin ... ,7601.html is useful. I usually go down to 12,000 grit, although a too high polished surface will prevent good paint adhesion. The graded sheets are also available separately. Regular very fine sandpaper is also a useful addition, but they don't go down fine enough for a really smooth finish.

[GazzaS]

I appreciate the link. I remember having something like that when I was a teen. I was hoping to find what might work from more industrial grade stuff at lower cost. You can get a lot of sandpaper from a hardware store for that price.

[Admhawk]

There are many factors that will affect the finish.

If you use really coarse sandpaper, it will create deep gouges that will be difficult to smooth

If you use some of the metal paints like alcad, they show almost every imperfection.

The thickness of the sprayed coat of paint and if it's glossy or matte will have an impact as well.

The standard items I use are black wet/dry sandpaper from an auto body parts store. 320 grit, used wet and 600 grit, used wet. I then spray with a matte enamel or acrylic, thinned approx 30-40% with the manufacturers brand of thinner. I don't normally see any imperfections.

If I am using metal paints or going for a gloss finish or using super thin paint, then I will wet sand progressively down to 10 or 20,000. Sometimes I'll even polish with some rubbing compound. Again, depending on what kind of Finish I am after.

[biggles2]

The gray-ish color hardware store grade sandpaper (i think it's called aluminum oxide) goes down pretty fine. And you're right, it is much cheaper! I also keep a supply of that stuff.

[biggles2]

To get rid of a rough patch, etc., work with progressively coarser grades, starting from a too fine grade, until the blemish disappears, then reverse the process again with progressively fine sandpaper until the sanding lines also disappear. That way you won't start off with too coarse a sandpaper making deep gouges, and giving yourself extra work trying to make them disappear, too.

[GazzaS]

Thank you, gentlemen. This project is actually for an older aircraft model that was molded with raised panel lines. I'd started with 600 grit wet/dry paper used dry because the raised details I wanted to keep we're masked for their protection. After that I went over with 1200 grit wet/dry also dry but still have a matte finish. Hopefully I haven't made any marks that will be difficult to remove.

I'll be airbrushing with Testors Model Masters hoping to get a satin finish. I haven't used enamels in quite some time (decades actually) having used Tamiya acrylics or been out of modelling completely in the meantime.