We are a knife manufacturer and we have etched knives with handles made of EXACTLY the same aluminum for years now without an issue.

We released a few new knives this year, 4 with black anodized aluminum, 4 with gold anodized aluminum. We put the 4 black in the c02 and we get the perfect white etch we have always gotten. We put any of the 4 gold in the same laser and I'm not exaggerating when I say, it doesn't even approach marking it. We have gotten gold aluminum for handles from the same source and not had this problem.

Here's where it gets super confusing. I moved the gold ones to a Fiber Laser and accomplished SOME sort of an actual mark. It's not super clear but at the PERFECT settings you can see and feel it so it cut into the metal.

Has anyone else experienced this? What causes it? Is there anyway to get these to etch? We really don't want to use Thermark because it's inconsistent and messy.