Josh Judkins added a forum post earlier in the year detailing how to reduce burn marks on acrylic. Here are a few more when’s and why’s specific to the use of protective paper on the material.
As a rule, the acrylic sheets that we stock are masked with protective paper, which keep the material free from scratches and making. This paper is a brown film with an adhesive coating and is applied to both sides of the sheet at point of manufacture. This means that, by default, all our stocked acrylic has protective paper on both sides, the exception to this being mirror acrylic, which is masked on the mirror side only (so you don’t get distracted by your reflection).
The protective paper on the bottom of the material must stay on to protect the material from heat flares during laser cutting. The protective paper on the top surface stays on if the design file contains heavy raster/vector engraving and/or cutting. However, if there is any light/medium raster/vector engraving, the paper is removed from the top surface, as anything other than heavy engraving does not adequately etch through the paper. This means that if you have multiple types of engraving in your design, for example heavy raster text with a medium vector outline or vice versa, the protective paper will be removed by default.
The above are our default procedures. Of course, you may wish to experiment, in which case feel free to make a request in shipping instructions if you would like to retain or remove the paper contrary to the normal option.
So why would you want to leave the paper on and then deal with peeling it off a whole lot of tiny pieces? The paper not only protects the acrylic from scratches and marks when the material is being handled, but stops the laser heat from discolouring the material surface during cutting. As you can see in the image below, retaining the paper until after the cutting is complete produces cleaner results.
Another reason to leave the paper on is if you want to fill your heavy engraving with colour. Make sure to leave the paper ON until your fill is dry. We have a forum post detailing the ins and outs of masking.
Here is some additional info on how to improve engraving results: