Summary

I created a personalized Pi nightlight for my daughter who loves math. I made it from a blank piece of 4mm thick circular clear acrylic and a LED base. 

 In order to etch acrylic, you will need to use some type of substrate that will absorb the light energy and transfer the heat into the acrylic. The key is to control this so you get the desired effect without burning the acrylic. I have used black craft paint and card stock in the past. Both work but require a lot clean up and usually result in scratches on the acrylic.

I have seen folks use anodized aluminum business cards to engrave acrylic but this limits the size of the engraving area. I have started using 10" anodized aluminum flashing for my substrate. I have been very impressed with the results and cleanup is so easy.