Laser Printing Residue on Medical Grade Silicon 1

We are using an Epilog laser to engrave on rubber, but the laser is leaving behind a residue in the engraving that is extremely difficult and to remove. We are currently using rubbing alcohol with a Q-Tip to remove the residue by hand and this requires several deep cleanings to get a sub-par result. This is very time-consuming and will completely bottle-neck our process once we are mass producing these items. Are there any suggestions on a better cleaner to use, or a better rubber material which won't stain? The rubber does not need to be medical grade, it just needs to flex and be comfortable on skin.
Top - Ring after initial engraving.
Bottom - Ring after 15 minutes of scrubbing. Still has white residue in some letters.