Restoring Glass

  One thing that frequently poses a serious problem for modelers is the clear plastic used in most kits to simulate glass. Sometimes these pieces are not packed separately in kits and can suffer from scratches. The occasional accident can also damage clear plastic; one slip with glue application, or a wayward fingerprint can ruin an otherwise great looking model. And modelers who specialize in restorations of old built kits know all too well the problems of old "glue bombs" that were assembled years ago with liberal applications of cement. If the parts are not actually cracked or broken, they can usually be salvaged. This article will show you some steps you can take to restore the clear plastic parts so that they look almost new.  

The three windshield pieces I had to work with when I was doing restorations of three original AMT '60 Ford convertibles were all damaged. (Click here for the full article.)

No. 1 had some serious glue damage in three places.

No. 2 had glue damage, scratches and old paint in both vent window areas.

No. 3 also had scratches and a deep pitted area where a drop of glue had been dropped on the surface and then wiped away.

You'll need a variety of tools for this project, including some sanding sticks. This is a set I got from Micro Mark.

I also used Flex-i-file Flex Pads in various grits, from medium to extra fine, plus their very handy polishing stick.

You can also find sanding sticks in various grits in the cosmetics section of most department stores. These are a bit wider than the tools mentioned above, and are handy for covering broader areas.

Assorted fine grit sanding sheets are also handy for working with curved areas.

For the final finishing and polishing, you can't so better than the Novus polishing system; in order of use: No. 3 Heavy Scratch Remover, No. 2 Fine Scratch Remover, and No. 1 Plastic Clean & Shine.

The severity of the damage will determine the coarseness of the grit you should start with. A general rule is to use the finest grit you can use and still get the job done. In the case of these particular windshields, because of the heavy glue damage I started with a medium grit stick. If you're tackling light scratches you may find that you can skip all the way down to using just the Novus products.

Here you can see some of the preliminary sanding on No. 1. In the case of heavy glue damage, there'll be a white spot in the damaged area. You'll need to continue to carefully sand until the white area disappears.
Here you see the preliminary sanding finished on all three pieces. The initial sanding will cause a lot of scuffing and scarring of the clear plastic. Don't worry about this; we'll clear things up in later steps.
After the initial sanding step, I changed to a finer grit stick and started sanding out broader areas to smooth out some of the rougher areas. The key to success is to work slowly through a successive series of ever finer grits.

Here's the result after sanding all three windshields with an even finer grit sanding stick than was used in the previous step. As you continue to work, you'll see the transparency slowly start to return.

Additional sanding with the finest grit sanding stick I had available resulted in even greater transparency. Extra fine sanding sheets also work well at this stage. You may find you'll want to use several different tools throughout the project, sanding sticks, sanding sheets, etc., depending on the shape of the area you're working on.

After all the sanding is done, it's time to switch over to the Novus polishing system. Start with the No. 3 Heavy Scratch Remover, and following the instructions on the bottle, start polishing both surfaces.

As you continue to polish with the Novus No. 3 you'll notice a dramatic increase in the clarity of the piece.

Once you've gotten things pretty well smoothed out, switch to Novus No. 2 Fine Scratch Remover for the final polishing. Again, follow the bottle's instructions.

You can also use a fingernail buffing stick to do a final clean up fine scratches.

The last step is to do a final polishing with Novus No. 1 Plastic Clean & Shine.

And here's the finished product. All that sanding and buffing pays off!

Back to the Tips & Tricks Index