I have a storm laser, Chinese made, and i need to make some name plates on the laser etchable plastic in green and a woodgrain. the problem i am having is that when i burn away the color to reveal the white, for the names, a black or colored residue is left in the white areas and it seems to be melted in. i have tried numerous settings from speed to the power and still get the same results. again the laser is a Storm laser cutting and engraving machine. any tips or help would be great thanks