First, create a piece of laser-cut acrylic that will fit into the plastic license plate holder. Measure and create a cutting pattern that represents the holder. Create your design by adding text or a logo to the cutting pattern. The engraving is done on the back side of the mirrored acrylic, so be sure to horizontally mirror the design so it can be viewed correctly in the front.
Mask the back side of the acrylic with a medium tack paper mask. Set the power and speed of your laser to create a .025- to .030-inch engraving depth. Remove any dust or debris from the engraved area and brush in an acrylic color-fill. Not all paints are friendly to this process. Use color-fill products designed for use with acrylic.
When the acrylic color-fill is dry, remove the paper mask. Apply a double-sided mounting tape to the back of the acrylic. Peel the paper off of the double-sided mounting tape and press the acrylic mirror on the plastic license plate holder. The mounting creates a durable bond in 24 hours for outdoor use.
—Mike Fruciano, Coherent