Polystyrene is the absolute classic model making material and with good reason: it is easy to cut, glues well, and lends itself to deformation. Models made from polystyrene should definitely be subsequently coated with varnish because otherwise they will tend to attract dust. In addition, a varnished model will have considerably more plasticity.
Straight or curved sheets can be made by means of scoring with a cutter or a scoring tool and subsequently breaking it along those lines. Good results will be achieved on sheets with thicknesses up to 2 mm using this method. In the case of thicker polystyrene it is advisable to break it along a straight edge in order to attain a straight clean cut. If you require that the cut surface be smooth it is better to use a circular saw. Circular saw blades produce the best results if the teeth are unset, conically relief-ground and have a low cutting angle (in the case of HSS blades, between 5 and 8 degrees; in the case of carbide blades, from 0 to 5 degrees). Round or more complicated shapes can be made by using a fret saw, scroll saw or a jig saw.
For the architectural model maker it is fairly easy to produce a layered topographic model using polystyrene sheets: each layer of sheet is covered completely with thin Double-Sided Adhesive Film, transfer glue or self-Adhesive Films and stacked one upon the other. When finished, the resulting visible layer lines should be brushed with a solvent, for example Dichloromethane, whereby the polystyrene “dissolves” into a uniform looking surface.
Small openings can be cut into facades when the PS sheets are no thicker than 0.75 mm. In order to produce a sense of depth, the sheets can be glued to solid objects made out of PS foam, acrylic or wood. Cut-outs from thicker sheets must be sawed or scored and broken through.