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A beginner's guide to building plastic model cars

Start with basic techniques to finish stunning model car kits
Building model car kits can be a satisfying pastime and hobby, enjoyable for young and old alike. To successfully complete plastic car model kits, you’ll need to develop skills and techniques that are transferable to other types of scale model kits. But the hobby also strengthens forethought, ingenuity, creativity, and determination.
When you pick your first kit, there are a few things to keep in mind:
  • Make sure the model car kit is all plastic. Do not buy one with photo-etched metal or resin parts — those are for experienced builders.
  • Pick a car whose finish can be a single color. Painting with spray cans is a good way to learn how to paint model car kits, and a single-color body and interior will be helpful.
  • There are thousands of plastic car model kits available. Choose one that interests you, so you’ll want to finish it. 
In this case, we’ll use an AMT 1/25 scale 1969 Cougar Eliminator because it has a limited number of parts and isn’t too difficult to build.
You’ll need a selection of basic tools when assembling model car kits, including A Tamiya Extra Thin Plastic Cement (No. 87182); B Loc-Tite Ultra Control Gel (or similar) superglue for bonding painted pieces and filling gaps; C sanding sticks in 180, 420, and 320 grit; D sprue or side cutters; E Tamiya Decal Tweezers (No. 74052); F a hobby knife with a No. 11 blade (plus replacement blades); G another hobby knife with a No. 17 blade; and H Bondo Glazing & Spot Putty (No. 907).
I use Tamiya side cutters (No. 74123) to snip styrene parts from the parts trees (also called runners, frames, and sprue) in plastic car model kits. Always align the nippers so the smooth back edge of the jaws faces the part you plan to remove.

Only a small amount of the sprue gate will remain, and it can be cleaned up with a sanding stick or a hobby blade.

Clear plastic parts, like windows, can be brittle and may crack because of the stress of side cutters. In these instances, I use a hobby knife instead and repeatedly pull the No. 11 blade through the sprue gate. You can achieve a similar result with a razor saw.
The injection-mold production process often leaves parts with a mold line created by the production tooling. (If that line is excessive, it’s called flash.) Remove mold seams from every piece before applying paint. Complex parts like car bodies require multiple molds, which can result in mold seams that run along each top edge of the body, and sometimes along the lower valences.
While it is recommended that you complete a build in the order laid out in the instruction manual, it is wise to jump ahead, perform test fits, and determine all the parts that will be body-colored, like this front valance. In some cases, those parts can be attached to the body earlier in the process. Check that attaching it in advance won’t impede the final assembly. Painting all these body parts in the same session is important to maintain consistent coverage, especially if your final color is metallic.
Liquid plastic cement works best on unpainted styrene. It’s easy to use: squeeze the parts between your fingers that are being glued, collect a generous amount of liquid glue with the in-cap applicator, and touch the applicator to the joint. Capillary action will pull the cement into the joint. Within 20 seconds, the parts will be joined.
Apply double-sided tape to the cap of a spare spray-paint can to hold the car body in place; you can use the same technique with craft sticks for smaller parts. Alligator clips are great for grabbing a tab, such as on a driveshaft. Are you painting something tiny with little or no place to grab it? Heat the tip of a metal pin with a lighter and insert it into an inconspicuous spot on the part.
Sometimes, locator holes for joining two parts are too small, partially covered, or nonexistent. You can open the holes with the tip of a sharp No. 11 blade, or you can enlarge one with a micro-drill bit in a pin vise. Note that a pin vise can be a useful tool as you gain experience, especially when you decide to enter the world of engine bay detailing, distributor wires, brake lines, and carburetor linkages.
Another use for a pin vise is drilling a hole to pin small parts that don’t have good attachment points, like side mirrors. Drill a hole in the mirror to accommodate a .024-inch diameter metal pin (piano wire or brass rod works). Drill a corresponding one on the body where the mirror belongs and glue the part in place.
With a flat, No. 17 blade, apply putty liberally to fill sink and ejector-pin marks, gaps, and any other areas that need it. Allow at least 15 minutes to cure and sand smooth with a 180-grit sanding stick. Depending on the size and shape of the repair, a second round of putty and sanding may be needed to completely eliminate the blemish. Any imperfections will only be amplified when primer and paint are applied, so be diligent.
Primer is recommended to help reveal any imperfections on the car’s body and to promote better adhesion of paint. Hobby paints are recommended because they are formulated specifically for use on plastic, although some automotive paints work, too. One rule of thumb is to stick with the same brand and line of paint to avoid mishaps. Tamiya primer and lacquer paints are readily available from hobby shops and online and work well. Priming the other subassemblies (engine, interior, suspension, etc.) is less critical and up to you.
When spray painting the body, I like to work from the bottom up in a snaking path until I reach the roof and repeat on the other side. I then spray the trunk, roof, and valances. Always begin and end the paint flow pointed away from the body, not directly at it, to avoid paint spatters. Typically, two or three coats of primer should sufficiently cover the body. If it feels too heavy or too light, experiment with the pace of your passes or the can’s distance from the model, which should be 6 to 8 inches.
After the primer coats, sanding with a 320-grit stick can eliminate imperfections you couldn’t see in bare plastic. This hood scoop should be perfectly smooth with a slight crest running down the center. The molded detail from the underside crept through and can be corrected with putty, sanding, and re-priming.
These Cougar taillights beg for dry-brush detailing. To use this technique, I dipped the brush into chrome silver enamel and wiped off the brush on a paper towel until most of the paint was removed. Then, with the brush at a low angle, I lightly drew the bristles over the raised portions until they were covered to my liking.
Applying self-adhesive Bare-Metal Foil is a reliable means to model stainless steel and chrome trim. To trim this window, I cut four sections of foil and placed them on the surround in the same fashion you’d find on the full-sized car: one upper, one lower, and two side pieces, with a sliver of overlap at the intersections. Use a new No. 11 blade to cut the foil and avoid tears. You can learn more about applying Bare-Metal Foil here.
Apply Vallejo Black Grey (No. 70.862) or a similarly dark-colored acrylic with a fine-point brush to body scripts. Next, employ the dry-brush method with a fine-tipped brush. Only the high points will receive paint and will contrast nicely with the dark color. Cover the molded side marker lights with Bare-Metal Foil and hand-paint the inner portion an appropriate clear color — in this case, Tamiya Clear Red (No. X-27).
While many modern kits include decals to replicate gauge faces, there is a quicker, simpler option: drag a sharp, white, colored pencil over the top, molded gauge detail. Do the same with a red or orange colored pencil for the needle.
Older plastic model car kits manufactured in the U.S. often lack locators between the body and interior bucket. Cut a length of sprue from the parts tree, line it with superglue, and insert it against a discreet junction of the two parts that won’t interfere with the chassis and that won’t be seen when the model is fully assembled.
Most plastic model car kits include water-slide decals. Trim the decal as close to the clear carrier film as possible using a pair of sharp scissors. Place the decal into a container of clean, room-temperature water for about 20 seconds. During that time, dab setting solution like Microscale Micro Set onto the desired location with a paintbrush.
Remove the decal from the water and rest one edge against a paper towel to wick away excess water. With light pressure from your thumb, check to see if the decal is ready to slide. Carefully and slowly slide the decal toward the edge of the backing paper.
Grip the decal with tweezers and place it on the model. The setting solution you added earlier breaks the water’s surface tension and allows it to settle against the model’s surface. If you need to move the decal, add a little water around the edges with a soft paintbrush and maneuver it into position.
When you’re ready to anchor the decal, touch the paper towel to its edges to wick away most of the remaining water and setting solution. Check for any remaining moisture bubbles and draw them out toward the edges of the decal with a paper towel, a thick paint brush, or a cotton swab.
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Essential finishing techniques for scale modelers.
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