Brown laser marks

[Laser]

Hi,

I am new to the forum and new to laser engraving. I have searched both the internet and this forum and can't seem to find any information on this topic. I have seen many laser engraved items online which seem to have a lovely reddish brown colour to the burn marks such as this:

https://gigaom.com/wp-content/uploads/s ... 04x536.jpg

The people creating these items claim to have done nothing special other than to have lowered their laser power. I am able to produce every tone from deep black through medium and light greys to "white" (unburnt wood) but all the tones I can make are shades of GREY not shades of RED-BROWN. How on earth are these brown tones being made? Am I missing something? Is the wood being coated in something first?

Any help anyone can provide me would be greatly appreciated.

[LINUS]

Because of the materials, plywood different layer have differet colors

[Laser]

Hi, Thanks for your response. A user on reddit says that it's because I have a diode laser and not a CO2 laser. I feel he may be right. Any thoughts?