What can a diode laser on my router cut or engrave, and what should I never put under it?

The short version

A blue diode laser works by being absorbed. Opt Lasers explains that dark, absorbing materials respond well and that transparent, white or reflective ones let the light pass or bounce off. That one rule explains most of the list below.

Works well (per J Tech Photonics and Opt Lasers)

• Wood and plywood. J Tech lists up to 1/4 inch and says to avoid oily or resinous species. Opt Lasers notes thin, uniform plywood cuts better than dense sheets.
• Paper, card stock and cardboard. Opt Lasers warns they burn easily, so use conservative power and watch the job.
• Cork (J Tech: up to 1/8 inch), real leather (up to 1/8 inch), felt and natural cloth.
• Dark acrylic, up to 1/8 inch per J Tech.

Engrave only

• Stone, slate, ceramic and glass take a surface mark but are not practical to cut (Opt Lasers). J Tech notes glass can only be etched.
• Bare metal: Sienci says diode lasers are generally not powerful enough to engrave it. Coated stainless, such as painted tumblers or parts treated with a marking spray, is the common exception.

Will not work

• Clear acrylic. Opt Lasers says clear, transparent and very light acrylic passes too much blue light to cut. J Tech lists dark colors only.
• Cutting sheet metal.

Never laser these

Sienci's list agrees on PVC, ABS, vinyl and fiberglass.

Pro tips

• PVC foam sign board is PVC. Route it, never laser it.
• J Tech notes that parts of its chart were written for CO2 lasers, so confirm any borderline material with your laser maker.
• Sienci's guide does not give leather cutting settings because leather shrinks and deforms as it cuts, which pulls it out of focus and raises the fire risk.