Scribing and Restoring Finish

[laval66]

So I'm finally to the point where I feel comfortable sanding off raised panel lines, laying down Dymo tape, and scribing away. It's actually coming along well, and I laid down some M4. Surfacer 1000 over my handiwork to see how it looks.

I can't lie, I'm pleased. But, I still have some evidence of my sanding left on either side of the panel lines. I polished with 12000 grit, but really didn't see a change at all. Ideas?

[Craig Baldwin]

You need the plastic polished for what, a Natural Metal finish product? A paste polishing compound like the Tamiya brand or other type of pastes should work. For straight paint 12000 is more than enough.

[laval66]

You need the plastic polished for what, a Natural Metal finish product? A paste polishing compound like the Tamiya brand or other type of pastes should work. For straight paint 12000 is more than enough.

I'm rescribing a C-130 in preparation for a coat of Blue Angels Blue - nice airshow quality finish. It's a long term project in between waiting on other work to dry.

[Craig Baldwin]

With 12000 grit paper, the surface may look dull but gloss paint will appear ultra smooth on it, even lacquer.

[lesthegringo]

One other way that I've used to get rid of those slightly furry edges that can be left is to dilute one part acetone with two parts isopropyl alcohol and let it wick along the scribed lines. The small amount of acetone just disolves the very fine edges without doing any more, and the alcohol tones it down and stops it from evaporating too fast.

Don't use pure acetone though

[Netz]

OOO steel wool will take out any scratches in your plastic, if your seeing scratches after 12000, you've basically polished your scratches.

You can use paint thinner to clean up your scribbing.

Curt

Edited October 20, 2015 by Netz

[dnl42]

Are you saying that you've got sanding marks on either side of the scribed lines? Your description suggests a smooth and polished surface around the scratches. If so, I assume those sanding marks are deeper scratches from a coarser grit. This is consistent with going to too fine a grit too soon. That is, you didn't go deep enough to remove the scratches, so they're still present.

In this event, you'll need to either: (1) fill the scratches then smooth or (2) sand the scratches out by removing material until the newly smoothed surface is the same level as the bottom of the scratch.

When sanding with successively finer grits, or filing with finer cuts, the goal with each grit level is to get the surface to a uniform state and rely on successive grit levels to eventually to smooth it all out again. You can see this process very easily when you sand a scratch out of a clear part. You start with a single scratch. Then you start sanding and immediately make it worse with even more scratches. But with each higher grit, the scratches get finer and finer and the plastic ultimately gets clearer and clearer. Once you've done 12000 grit, you switch to a buffing stick or polishing compound to get that clear-as-possible finish.

Fill or sand out depends on the circumstance. In this case, filling seems the better approach to preserve your scribing. Perhaps fill with Tamiya fine or some other filler where you can do the "rough" shaping with a cotton swab and appropriate solvent and then the last bit of surface leveling with a fine sanding stick. Alternately, you could use CA as a gap filler. Let it cure and then carefully sand out. Don't wait overnight though as the CA will become too hard. I use both of these approaches depending on the phase of the moon :)

HTH