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Working With Clear Polystyrene Parts and Kits

Working With Clear Polystyrene Parts and Kits

  by Andy Slater

We've given clear polystyrene its own separate document on this site because it's a bad idea to treat it as 'just another part of a kit' because it behaves differently and should therefore be treated differently.

Glueing

The problem is that ordinary polystyrene cement will crazy any area of clear plastic that it comes into contact with so there is little margin for error. If used, it is probably best to use liquid cement by dry fitting the part and applying the cement to the joint with a very fine brush such that a tiny amount is drawn into the join by capillary action.

Even the vapour from drying cyanoacrylate glue will cause misting to clear parts and although it can be used with care I can't really see much point in taking the risk.

White glue will hold the part in place and although it won't give as strong a bond as CA or polystyrene cement, it dries clear and it won't damage the clear plastic in any way.

Dealing With Scratches

Many people don't realise that you can sand a clear part and then polish it back to its transparent state and, although it requires a lot of effort, it is possible and can be used to remove scratches.

The first stage involves sanding the part with progressively finer grades of "wet-and-dry" paper. Each grade effectively removing the scratches left by the one previous, start with 600 grade and work up to at least 2000 grade (obtainable from car body repair shops). Use plenty of water or even do the sanding under a running tap. Unfortunately this arduous process pretty much has to be done by hand as a motor tool would be too aggressive.

A motor tool can be employed for the second stage in which a buffing tool or soft cotton cloth is used in conjunction with a very mild abrasive (like toothpaste) to buff the part to a high shine.

Tinting

The best way to tint a clear part is to airbrush it with one of the special clear colour paints or with a mixture of varnish and coloured ink.

Some aircraft have metallic tinted windows and this can be replicated by airbrushing the inside of the canopy with some on the almost clear carrier fluid from a tin of metallic paint that has been allowed to settle.

Painting

Sometimes, with aircraft canopies for example, it is necessary for areas of the clear plastic to be painted. Ordinary enamel or acrylic paint may be used and other than the obvious strategy of attempting to apply the paint only where it's needed in order to achieve the required finish, two strategies exist:

The first is to prevent the paint from getting on to areas where it isn't wanted. This can be done using masks made either from tape or created by painting masking fluid (latex) onto the areas that are to stay clear. Another technique is to use a sharp point to engrave a line around the edge of the area to be painted in order to stop the paint from flowing beyond the engraved line. By this method it is possible for example to define the border between cockpit canopy and frame to a degree that the moulding process is not able to do.

The second strategy is to remove excess paint after it has dried. The trick is to make a tool by cutting a piece of acrylic rod at a 45° angle and using it to chisel away the excess paint. The cutting edge of this tool should be sharp and smooth enough to remove the paint but not hard enough to damage the plastic.

This article is copyright (C) Andy Slater and is used here with permission
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