The most common problem with the CerMark process is when the mark washes off. This is caused by laser power and speed settings not being correct, the laser is out of focus or optics need to be cleaned.
Every laser is different and you will have to do testing on your system to determine specific power and speed settings for each laser.
Different types of metal require different power and speed settings. hard metals like stainless steel are easier to mark then softer metals like aluminum and copper.
Many times brass and copper items will have a clear coating on them to prevent tarnish. These coatings prevent CerMark from bonding to the base metal.
Below is an instructional video related to the use of CerMark marking materials in liquid form.