I’ve tried a bunch of ideas, and it burns through regardless of power. I saw another post with awesome results, though I can’t replicate them.
1000 speed and 50 power as they suggested makes a visible image, but burns through the canvas completely. I tried cutting the power to 20, and while it was still burning through the canvas, the image was not legible.
Visibility means char. Slow down dramatically (say 200) and see what happens with power 1. Ramp speed down and power up as needed. But at high speeds you’re ablating material without making the remaining material hot enough to darken.