Can I engrave on this or that?

Wow, this laser engraving head is so powerful that it can cut through a sheet of paper! What else can I do with it?

To answer this question, first we have to explain how laser engraving works. The principle of laser engraving is carving a trace by burning the surface with powerful laser.
Thus, the sufficient and necessary condition for laser engraving working on specific material is that the material can absorb the heat generated by laser and its ignition point is not too high.

Now that you understand the principle, we can figure out what kind of materials can NOT be engraved on.

1. Reflective materials
    These kind of materials will reflect the laser and absorb nothing, thus is not
    suitable for laser engraving. Mirror is the best example of this kind.

2. Transparent materials
    The laser will go right through these materials and left no trace. Materials like    
    transparent acrylic is a difficult job for the laser toolhead.

3. Incombustible materials
    Metal, glass and all of the incombustible materials require super high power laser to
    carve. Actually, you will need at least 1000 times stronger laser.

We can conclude that the best material used should have low ignition point along with matte and flat surface for efficient laser energy absorption, such as cork board or leather.

Here we also provide a easy (but not 100% precise) method to judge if a material is usable or not: take a lighter and place the object on the fire for several seconds, and if it is scorched then laser will likely work on this material.