Acrylic is a great material for laser cutting as it vaporizes when cut rather than burns which is what allows it to get that nice flame-polished edge. Acrylic sheets are generally sold in metric which is usually a little bit short of the standard dimensions they are sold as (3mm acrylic sold as 1/8″ is only .118 rather than .125″) and different manufacturers have different measurements as to how much an individual sheets can vary from the stated thickness (also called the tolerance). This can make a big difference for projects like topographic models or boxes when the sides need to slot together so it’s always good to check out ahead of time.
This is the acrylic you want to use when you are engraving as it leaves a nice white mark on the surface with a high contrast on all colors except white. The edge quality is also good so you can definitely cut it as well. We have found that cast acrylic usually comes with a paper mask but not always.
Generally extruded acrylic is a little cheaper because of the production method, it is a fine choice for cutting but avoid it if you are planning on engraving a design into the surface. We have found that this usually comes with a plastic mask but again not always.
Mirrored acrylic is generally a one-sided 3mm (1/8″) sheet that is a colored or clear acrylic with a colored mirrored paint applied to the backside, it is possible to get it in other thicknesses but that is usually a special order, they also make double-sided mirrored acrylic as well, but again most likely a special order. We usually cut mirrored acrylic from the backside to reduce the laser beam reflecting back up from the table and causing some havoc.
We generally like to leave the masking on and engrave through it to keep the top surface clean of the residue produced during engraving, this masking can also double as a paint mask if you are planning on doing a paint fill of the engraved areas. If the mask is plastic we remove it and replace it with a paper mask aka transfer tape which you can get at a screen printing supply or art supply store. The result on cast acrylic is generally a white mark which can be back or edge lit to make a nice looking sign. For colored acrylic we have to engrave it on the front side, for clear acrylic we generally will reverse the design and engrave it from the backside as this makes a cleaner finished product.