To All League Bowlers:
Effective August 1, 2019, USBC rules now state that you may no longer clean your bowling ball during competition with a liquid or any other foreign substance (this includes rosin bags). The only time you may clean your bowling ball with a foreign substance like a cleaner is before or after competition. You may only use a dry towel/shammy to clean your ball during competition.
If your bowling ball comes back from the pinsetter and has grease, marks, or other substance that was left by the insetting equipment, please do not clean your bowling ball yourself. Take the affected ball to a league officer so that he/she can clean the affected area with a USBC approved cleaner.
Below are snippets from the USBC rule book for 2019-2020 which is also available on bowl.com.
If you have any questions about this rule change, please contact one of your league officers.