More than likely, when your engraving doesn’t produce a frosty white effect, this is caused by using the wrong acrylic in the application.
Cast acrylic sheets and objects are made from a liquid acrylic that is poured into molds that can then be set into various shapes and sizes. This type of acrylic is ideal for engraving because it turns a frosty white color when engraved, making it suitable for awards and plaques. It can be cut with a laser, but it won’t give projects flame-polished edges.
The other type of acrylic used in laser engraving is called extruded acrylic, which is formed into sheets by a machine. Extruded acrylic is generally less expensive than cast acrylic because it is formed through a higher-volume manufacturing technique. However, it does react differently with the laser engraving machine. This type of acrylic cuts cleanly and smoothly and produces a flame-polished edge; however, when engraved, it doesn’t produce that frosted look, but rather a clear engraving. Make sure you are using cast acrylic if you want a frosted white finish.