I'd start with soapy water, isopropyl (rubbing) alcohol, and WD-40 since those are generally not harmful to rubber.
A lot of solvents can damage gum rubber, so if you need to resort to something else, read the label carefully. Goof-Off works great on a lot of stuff, but the FAQ on their web site specifically mentions that it can damage natural materials including rubber.
Word of advice- stay away from spray cleaners like Fantastic and others, they'll break down the rubber over time and you'll be drumming on a flaky mess.
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DCI, DCA, WGI, done it all in some form.
i wouldnt use alcohol either it could dry out the rubber and it will crack becoming useless
_________________________ http://www.freewebs.com/motorcitymarauders/index.htm Motor City Percussion Snare line 2002-2007 Pine River High School percussion instructor 2005 Laingsburg High school Percussion Instructor 2006 Wayne Memorial High School Snare Tech 2005-present