|By John Lester - images & text © 2007|
Working with clear parts, whether injection molded or vacuformed, is often frustrating. It doesn't need to be. Here are some things I've learned over the years that I hope reduces those frustrations:
The first thing I do when I get a model is dig out the clear parts. If they are not already in a separate bag, I round them all up and place in a zip-loc plastic storage bag. This helps keep the parts from being scratched as they rattle around in the box - and prevents small parts from making their escape before I'm ready to work on the model.
When it comes time to work on a model's clear parts, I first polish any scratches out with plastic polish (Novus, Tamiya, Micromesh, etc) or toothpaste (not gel!) I do this the same way you polish brass or your car, using a soft cotton cloth, a small amount of polish and rubbing in small, circular motions. Deeper scratches may be sanded down with fine grits of sandpaper or sanding sticks (Squadron.com has a tri-grit sanding stick especially for polishing clear parts). If I have to do this, I start with 400 grit and work my way down to 1200 grit. Sandpaper this fine may be found at automotive supply stores, or wherever auto finishing products are sold.
It's often easiest to do all this while the part is still attached to the sprue/backing. If loose, back the part with modeling clay or silly putty to prevent any cracking/bending. (and if, heaven forfend, the clear part cracks - you'll need to polish and Future that much more.)
Injection molded clear parts are brittle. Use a razor saw or hobby knife (I use one of Hasegawa's small photo-etched steel saws) to remove them from runners. Cut away from the part, then sand/trim the excess gate away. This helps prevent cracks or divots that you'll have to try to fill.
I use a small scissor to trim vacuform parts from their backing. You want to leave excess material all around, then sand/trim the excess away. It helps to outline the edges of the part with a permanent marker, so you have an idea of how far to go with trimming. Sometimes a manufacturer will include a resin "plug" for the part; if so, it makes it easier to see what needs to be removed.
Whether you're using an injection-molded or vacuform part, test it's fit to where it will be affixed continually, until the part fits exactly how you want it. This is especially important with vacuform canopies. To aid in aligning and gluing vacuform parts, use thin styrene or wire strip as a “rail” (either affixed to the clear part or to the model). This rail can also help prevent windows from falling inside the model (always a pain in the butt when it happens).
Glass and Frames
I dip all my clear parts in Future/Kleer (a clear acrylic floor polish) for a more “glass-like” appearance. First, I clean the parts throughly beforehand with ammonia-based window cleaner (such as Windex). Then, holding the part at a corner with self-locking tweezers or hemostats, I dunk it in a small cup of Future. I let the excess drip off, then dab any remaining excess off with paper towel. Goofs can be stripped with that ammonia-based window cleaner. Now - LET SET FOR 24 HOURS before handling!
Most model guides tell you to cut small strips of tape to mask the areas that supposed to stay clear before you start painting. I do the reverse. I cut strips of tape to cover any framing, then mask inside the frames with liquid mask (Maskol, MicroMask, etc) as an alternative to the traditional way. Carefully peel the tape away before the masking agent has fully set - or if too late to do that, run the tip of a new hobby knife blade around the edge of the tape strips to set them free from the liquid mask. On small scale models, the tape can stay on to provide more distinct framing (and cover any gaps!). One thing to remember when painting is to paint the INTERIOR color first, so that when you look through the part to the other side, you'll see the interior color.
Sticking It On
I generally mask off all clear parts, then attach them to the model before I begin painting the color coats. This enables me to fill any gaps and make any adjustments to the fit without having to repaint any parts of the rest of them model.
Solvent glues and putties (like Bondo glazing putty or any of the Squadron putties) will distort and/or craze clear parts. Use these only where you do not have clear butted against the rest of the model (i.e., there's a frame you can paint to cover any distortion). Vapors released as superglues cure can leave a white residue, even with adequate ventilation. Unless I need the strength of superglue, I generally use white (“Elmer's”) glue to affix parts. This can also be used as a gap-filler (you can smooth and blend with a q-tip/cotton bud), as can epoxy putties (milliput, Aves, etc). In some special circumstances where you don't need a strong bond - like when attaching clear acetate to the back of an instrument panel - you can even use Future to affix the parts. Just paint it on and press the parts together.
Sometimes you'll run across the need to make a new clear part. For canopies, you often have no choice but to use the existing part as a master (or carve a new master) to make a vacuform or heat-n-smash replacement (techniques which are out of the scope of our present discussion). But for windows that are set inside a heavy frame or a hull/fuselage, and don't curve much, you can try a different approach. First, lay a strip of electrical tape against the inner surface of the area where the window will go. Then, mix up a batch of clear resin (Envirotex or similar) or 15-minute epoxy glue. Use a toothpick to place the resin/epoxy into the opening, being carefull not to transfer or create any air bubbles (and to wick away any that sneak in). Once the resin or epoxy has THOROUGHLY cured (at least 24 hours), you can polish and Future the window area as you would any other.
Some folks also have good luck with superglue for this process, but I find it never really cures completely clear for me.
There you have it - techniques for making your clear parts shine. I won't guarantee that the job won't still be tedious and unforgiving, but at least it should not be so daunting!
This page copyright © 2007 Starship Modeler. First posted on 4 June 2007.