I imagine that if you remove the valve core and flush out the inner tube of talc powder before putting in things like stans tire sealant you may have better results. I don't know if something like vinegar, water or whatever would be better for rinsing the inner tube out, but I am sure even just plain water rinsing would be better than nothing. It also seems that these tire sealants dry up over time, which seem to be an issue. My imagination suggests that the talc powder would indeed simply absorb more moisture and accelerate this drying effect. My suggestion, after rinsing the talc out, is to add a little fluid to the mix or don't do a perfect job ringing out the inner tube after the last rinse. The extra fluid might prevent the sealant from drying up. Maybe once a month or two or so, you might inject some fluid (I don't know if water, some kind of anti-freeze or something else would be better) into the inner tube to prevent it from drying out. http://www.amazon.com/Stans-Tubes-2-Ounce-Sealant-Injector/dp/B001GSKL4A/ This might be the tool I'd use to inject fluid. Instead of pure fluid, maybe you'd use a 50/50 mix of fluid and sealant when you add more, I don't know what would and wouldn't work, this is just an inexperienced guess.