jim8flog
Journeyman Pro
Definitely not allowed on the club face in the current or 2019 rule
2019
(3) Deliberately Changing Club’s Performance Characteristics During Round.
A player must not make a stroke with a club whose performance characteristics he or she deliberately changed during the round (including while play is stopped under Rule 5.7a):
. By applying any substance to the clubhead (other than in cleaning it) to affect how it performs in making a stroke.
2019
(3) Deliberately Changing Club’s Performance Characteristics During Round.
A player must not make a stroke with a club whose performance characteristics he or she deliberately changed during the round (including while play is stopped under Rule 5.7a):
. By applying any substance to the clubhead (other than in cleaning it) to affect how it performs in making a stroke.