The surface is not yellow after engraved and display the material background color, leather cutting edge is not black.
Parameters Set: Engraving speed depending on the graphics size, small pattern can be slower speed, the big pattern speed can be faster. Natural leather cut a little more slowly.
Work Effects: If you use laser cut natural leather with air flow, the cut edge easy to be black. After cutting you could use plasticene pick it off.
Another way is flow nitrogen when you are cutting leather. This will stop oxide on leather, without yellow or black.
Different leather, choose different cutting methods. Such as artificial leather, Drop it in water first and then cut or engrave. Natural leather, you could paste a crepe paper at the cutting place to prevent cut place yellow.