do I need to used contact paper to etch anodized aluminum?
In short …no
Thank you Sir.
“Etching” aluminum doesn’t remove any material, it only ablates the dye from the surface oxide layer. This means that no masking is needed since there is nothing to redeposit on the surface.
Side note: you should NEVER use contact paper in your laser cutter unless you’re dead certain it doesn’t contain PVC. CON-TAC brand is made of PVC.