Hi Bob
For slate it really depends on what you are engraving. For simple black and white images you can generally do a straight engrave, if it’s more of an image you may need to invert the image to get a better result. You can also vary the resolution based on the image as well, I used 8k for the review test frequency of 26, power at 40% and depth at 30%. But you can play with those settings to get various shades on your engraving. Lasers are a ton of fun but can take a bit of playing around.