Bright dots when engraving acrylic

I have been trying to find the right settings for engraving on 2mm clear acrylic. I am using a Longer ray 5 10w. I am engraving using black card stock under the acrylic and coating the down side with dish soap. I have run multiple tests with the similar results. The last test was 4 of the same gaphic on one 5x5 peace of acrylic. with the following setting 4000mm/min at 25%, 5000mm/min at 25%, 6000 mm/min 25%, and 7000 mm/min 25%. All with similar results. The 5000mms/min was the best with very small hot spots. I have tried both 35% power and got bad burning. I have tried 20% power, and still get burning, with a to light image.
Anyone have any advice

i have never heard of this technique
Usually black acrylic (water based) paint on the TOP surface helps

Remember though, diode lasers are 445nm visible light, having them work on translucent clear acrylic is… a “hack” :smiley:

During my youtube dives i have found a number of people using black card stock some with soap some not. And of course all their work turns out great. i have see a few using back paint. That might be worth a try, One coat on the up side of the acrylic?
Thanks for the reply

2 light - cross hatched - coats of water based black paint on the side you want to engrave. thats will act as a substrate for the laser to act uppon.

Water based so you can clean it with tap water and not chemicals - which would otherwise stain the acrylic.

Milage might vary of course based on paint, acrylic type etc

Thanks again
Ill give that a try

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Try Ironlak Fraiser (wht) or Matt Black (blk) if you can find it. White works because if the TiO2 in it. I got mine at Michael’s but I think Amazon has it. I used ir for doing shot glasses.

thanks Mike, ill look for it and give it a try. my current results are frustrating to say the least