Extruded acrylic is made by melting acrylic resins in a machine and using the liquid to fill a die. The acrylic is then forced through rollers to give an even width and finish. It has a more constant width than cast acrylic, and it’s better suited to being vacuum shaped, bent and heated, but it can be more susceptible to cracking in some situations. However, good quality extruded acrylic (such as Perspex) gives a very clean, smooth edge when laser cut.
Extruded acrylic is factory made in sheets, so it tends to be cheap. It’s mostly suitable for people who need straight, flat pieces. When extruded acrylic is laser cut or engraved, the surface does not change colour, so it’s ideal if you’re looking to produce clean shapes.
Cast acrylic is made by being moulded between two sheets of glass; a rubber gasket is placed between the two sheets to determine the thickness of the acrylic as it cools. Because this is a less exact method of moulding, the tolerance (thickness) of cast acrylic varies more across a sheet. It is more expensive than extruded acrylic, but it’s also more versatile.
Cast acrylic is very strong and will not warp when heated. It copes well with impacts and resists scratching. When engraved, it turns a smooth, frosty white colour, so it’s popular in the manufacture of awards, plaques and trophies where the engraved surface needs to be visible through the piece.
Acrylic quickly becomes statically charged, and static can attract dust, lint and dirt from the air. This can make acrylic pieces look unsightly, and it’s almost impossible to prevent with normal cleaning. However, you can use anti-static or silicone lubricant spray on your piece to prevent it from attracting dust; remember to reapply the spray every few weeks.
Before applying any anti-static product, it’s a good idea to remove clinging dirt to prevent abrasion damaging the surface of your piece.
Acrylic can sometimes acquire hairline cracks across the surface as a result of stress or chemical damage. Not only does this make the acrylic weaker, but it can dramatically affect its appearance.
Some acrylics, such as Plexiglas, come in craze-resistant forms. However, the best way to prevent crazing is to avoid using certain types of cleaner and avoid subjecting your piece to impacts or stress.
Always use non-abrasive fabric to clean acrylic, such as a lint-free anti-static or microfibre cloth. If the surface is dirty, use a small amount of mild detergent and don’t put too much pressure on the acrylic as you clean it. Don’t use any household cleaners that contain alcohol, bleach or ammonia, such as window cleaner. The surface will almost certainly craze, and thin pieces may shatter completely.