Dear,All blue laser need paint or marking black paper t if you want engrave on glass or other reflective acrylic product. Because these transparent materials can transmit light, I have sent you the picture of the engraving scope of this product, which clearly states that it can be engraved after painted or stick marking paper .I did not confirm with you the number of engravings needed, this is my problem. But I've told you that I want to do what I can to solve your problems without giving me bad comments without discussion.