Question of filling molding spots / holes

Puttying up marks left by knock out pins is one of my least favorite modeling chores. Twenty years ago, a tip from FSM magazine was a bit of a game changer - use a punch and die set to pop out a disc of styrene, then glue it in place and sand it flush. There's never a worry about shrinking putty or the mess that process creates, plus it's so much faster than waiting for things to cure up hard enough to be sanded and the plastic blends in better under a coat of paint than putty.

From your photo, it appears as if you need another coat of putty - some of those pin marks are still recessed and need to be built up to where things are level with the surface. Another light coat of putty will help there.

Remember that paint doesn't hide sins. If you can see it with the naked eye in bare plastic, then it will show through primer and paint. 

Tube putty always shrinks as it dries. Always overfill and let it cure for a day or two before sanding. You can mask around the holes with tape, fill to the level of the tape before smoothing (while wet) and let it dry and cure before sanding it out. You can use general-purpose masking tape for this, as the thickness is not an issue and actually can be helpful.

Alternatively, epoxy type putties generally cure with minimal shrinkage and in the case of the quicker curing ones, can be worked within a couple of hours.

Hello!

I usually use molten sprue or CA for filling those holes. Molten sprue (dissolved in lacquer thinner) needs a few hours to harden and shrink, but after that it can be sanded really nice and smooth. CA works faster (hitting it with lacquer thinner accelerates the curing) but can be more problematic when it comes to porosity or difference in hardness between the filling and the surrounding plastic.

Hope it helps, good luck with your builds and have a nice day

Paweł

I too overfill most of those depressions, to allow for shrinkage.  The exception, however, is if there is a lot of junk around the spot that would prevent sanding, filing or scraping. In that case I fill even, applied by screwdriver or whatever, to get it level. It will shrink, so you may need to do this several times, but if you want good results, it is worth the work.

Don Stauffer

The exception, however, is if there is a lot of junk around the spot that would prevent sanding, filing or scraping. In that case I fill even, applied by screwdriver or whatever, to get it level.

Don,

What you can do in thiese cases is do the major filling as you have described, using conventional putty. Allow to dry/cure and add the top layer as required using Tamiya Liquid Surface Primer (in the jar, not the spray can) to correct any shrinkage. When this is dry, you can smooth with a swab or paper towel moistened with denatured alcohol. Afterwards, any sanding required should be able to be achieved with a few light swipes of a high grit# wet n dry.

Okay, thanks all!  As mentioned this is  the 1st time trying it.  A lot of good tips here.  As mentioned, I most likely did not use enough so i've added a little more and will report back.  I especially like the punch and die idea.  Maybe another tool to seek out....  

A drop of CA followed by an excelerator, then sand.

Good advice. I'll just add that I use Bondo Glazing putty, single component in a toothpaste tube. It really doesn't shrink and it dries pretty soft.

And also the advice to mask. Critical. I always mask just as close as I can to the edge of the problem, for the reasons that were stated. and also to protect the plastic in the initial putty removal before the finer sanding. In this case you would punch slightly oversized holes in tape and place the piece with the hole over the ejector pin mark.

In some cases, and it's not relevant here, it might be easiest to laminate a thin piece of plastic over the entire part. I've done that in spots like deep between two ribs inside an aircraft or inside bulwark of a ship. A little piece the full width of the space between the ribs, nice and smooth.

okay, now i see why the masking.....  oh well, practice makes perfect or hopefully at least, better.....  All I can say for this 1st try is that im glad its on the inside