Fabrication Techniques With Sheet Materials

Additive Process --Baking Clay Construction

Subtractive Process With Carving Foam

Subtractive Process --Woodworking

Finishing Process --Painting

By Jim Janish

Fabrication Techniques-
With Sheet Materials

Styrene
Styrene like all plastics, comes in a variety of thickness,(styrene measurements are based on millimeters). Before starting, think about the easiest way to build your object, keep in mind that some pieces can be cut after they have been joined. The easiest way to cut styrene is to first score the surface and then bend the material back and forth along the score to break it. The cleanest joints can be made by applying the solvent to the inside of forms. If you are using tape on joints be careful to not let the solvent leak into the tape, as it will melt the plastic underneath. After your joints are made a sanding block can be used to more accurately smooth your joints.
WARNING- Under no circumstance should you let the solvent get into contact with your skin, the solution is absorbed directly through the skin and can cause liver damage.

General Fabrication
There are many other planar materials that can be used in fabrication, ex. illustration board, Bristol board, foam core, etc. Single glues or combinations of glues can be used, ex. Uhu, Bond All, white glue, and hot glue. When doing illustration board construction spend an extra dollar or two and buy board that is a solid color all the way through, usually in black or white- this board will not separate, like other boards. Illustration boards have a grain and will bend easier in one direction, try to use this to your advantage. For tight bends, with illustration board, scoring the back of the curve will help keep the board from creasing.

Tools and materials for styrene projects:
Styrene .060 and .020
Styrene solvent (glue, cement)
Solvent applicator
Knife (a small Olfa brand with break-away blades works well)
Cutting edge
Approximately three grits of sandpaper (+/-100, 350, 600)
Hands (preferably yours)

Additive Process
--Baking Clay Construction

Sculpey- Baking Clay
Super Sclupey is the cheapest and easiest sanding baking clay. After being cooked baking clays can be added to and re-cooked. Before starting think about the easiest way to build your object, keep in mind that armatures and fillers can be used to support your form or save material, (aluminum armature, metal, glass, stone). The easiest way to work baking clay is to first make your form as accurately as possible, bake, and then use tools (Dremel, sand paper, files, and spackle) for refining the shape. For shape refinement after cooking, joint compound, spackle, bondo, epoxy, and epoxy steel can be used as fillers. To prep baking clay for final painting it should be fully primed and worked to around 600 grit paper. Sculpey can be primed with any kind of primer. Two part epoxy and super-glue work very well with baking clays.
WARNING- It is highly recommended that you avoid the fumes produced while baking Super Sculpey. It is also important to avoid inhaling the dust from sanding, either wet-sand or use a good respirator (cartridge style).

Tools and materials:
Super Sculpey, baking clay
Spackle from hardware store (not light weight or vinyl)
Medium paint brush
Approximately three grits of sand paper, the finer papers should be wet-dry paper (+/-100, 350, 600)
Sandable primer
Any type of paint you choose
Two part epoxy
Dremel tools are not absolutely necessary, but are a great investment for model building purposes, (average price around $85; includes large selection of bits).
Airbrush - airbrushes are the best way to achieve the exact color and finish that you desire.

Subtractive Process
With Carving Foam

Balsa Foam
Glue with almost any glue (tacky craft, yellow wood, epoxy).
Prime with oil or water based primer.
Any paint.
Cut with saw, knife, or push cut with metal tube.
WARNING- It is highly recommended that you avoid breathing Balsa Foam dust, wear a mask or respirator.

Blue Foam (Extruded Polystyrene)
Cheaper than balsa foam.
Cut with thin blade knife, band saw, hot wire.
Glue with contact cement.
Finish with several coats of filler, sand, prime.
CAUTION - Many spray paints/primers dissolve blue foam, even through a layer of joint compound. Water based paints and Testors brand will not melt blue foam.
WARNING - Avoid breathing blue foam dust and the fumes released when cutting with a hot wire.

Tools and materials for project:
Balsa Foam
Filler - joint compound or spackle from hardware store (not light weight or vinyl)
Medium paint brush
Approximately three grits of sand paper, the finer papers should be wet-dry paper (+/-100, 220, 400)
Sandable primer(automotive)
Small files, rasps, dowels
Dust Mask. We strongly suggest investing in a respirator with cartridge type filters.
Patience

Subtractive Process
--Woodworking

Basswood
Water based primers may warp wood so stick with oil based. Wood absorbs and gives off moisture throughout its' life, therefore, always seal the ENTIRE wood object when applying finish. Never just prime or paint one surface, it may warp. Many different natural woods and human-made "wood-like" materials are available and may be appropriate to use. Basswood is a good choice because it is easy to machine, shape by hand, and finish. Sand wood smooth(~220 grit) and seal the surace with sanding sealer or spackle. Prime with oil based primer and apply any paint. Do not wet sand unprimed wood.
WARNING - Avoid inhaling saw dust, wear a respirator.

Tools and materials for project:
Basswood block
Power and/or hand tools: saws, sanders, rasps, etc.
Approximately four grits of sand paper, the finer papers should be wet-dry paper (+/-60,100, 350, 600)
Spackle (not light weight or vinyl) or sanding sealer from hardware store
Sandable primer (preferably automotive)
Any type of paint you choose
We recommend a good respirator (cartridge style)
Confidence
Perseverence
Energy

Finishing Process
--Painting

Painting
The best finish will be achieved through starting with a well sanded, well primed surface. If restricted to canned sprays-- automotive primers work the best as far as drying time and sandability. Use care when mixing brands of spray paints, do a test piece because some paints are not compatible. Automotive spray paints and Testors brand spray enamels work very well for finish coats. If your looking for a high gloss finish consider using a final clear gloss coat and do not paint on humid days or nights. The best approach to color: mix your own paints / pigments, to achieve desired color brush or airbrush the colors on your model. Control the amount of gloss - clear top coats are available from matte to high gloss lighter, gloss surfaces will read more form, where darker, flat finishes will hide more defects. For airbrushing use acrylics. Acrylic paints (medium and pigments) and good water based primers are available at most art supply stores. Oil based paints are also available for airbrushing, but are more difficult to clean up. Bottom line is that you can paint with anything you can control, and you can learn to control anything you want, so don't limit yourself.