I was making valentines gifts for my nieces and tested it on cheap dollar store mirrors. The mirrors were only $1.31 a piece after tax and took just over a minute a piece to engrave. Make sure to remove the frame before engraving your mirror. Make sure to engrave through the back of the mirror so depending on the project you may have to reverse your image by hitting reflect on your image. I used 30 power, 70 speed, and 140 for line. You may need it to be more for grater detail but I would stick to the speed and power. Engrave right through the paper back of the mirror. NEVER leave your machine alone just to be safe but it shouldnt burn the paper back on the mirrors.