Some colors like teals, some blues, and especially red seem to need a harder hit because it blocks or absorbs the laser.
I have had to drop speed to 800./80 or 500/100 for an engrave in one pass on particular colors.
Experimentation is the key. For instance, the red/white debris seems to almost act like a dye pack and tints the exposed white engrave. A normal engrave of 1000/60 followed by a low power ‘clean up’ second pass will resolve this coloration problem.
These numbers are my go to start parameters, but as mentioned, sometimes they may need a little nudge.
So, I ended up scraping the first sign and testing the material (like I should’ve to begin with) for cuts and engraves. It ended up needing 1000/full for engrave and 300/full with 3 passes to cut. Good thing was I got the time down to 46 min from 2 hours which is a lot better with the plastic smell. This is an outdoor sign for my fence so I’m okay with the level of detail. I won’t be using this material again though for high quality projects. As always, thanks for the guidance!
I’ve noticed that dust from the top color layer tends to blow into the engrave and makes it look stained. I discovered blasting the engrave with a stream of alcohol from a squirt bottle washes it out.
Water may do the same for all I know, my bottle happens to be full of alcohol.
That 5 power cleanup only works if the time to make another pass at low power is not a problem. I work a lot with tiny designs, but a long engrave for a sign may be the time to give it a squirt.
As mentioned, I have only seen the crazing on transparent materials. I have sprayed some alcohol on a napkin and wiped the backside of earrings that had flash on them (because I was not bright enough to mask the back - d’uh). Never saw a problem with the solid two color stuff.
But a few of the clear acrylic I have wiped did indeed craze. Some physics to explain this, I am sure, but I do not have the data.