This is an aside, maybe it might apply to some of you commuting on mountain tires.

Many mountain bikers run Stans Sealant in their tires for sealing of tubeless tires, automatic sealing of pinch flats, thorn punctures, etc. (roadies don't use Stans because it does not work at the higher tire pressures). Also you can buy "slime tubes" that have the sealant already added.

Turns out that CO2 causes the sealant to congeal into a rubbery lump. One of my buddies recently used a CO2 cartridge to inflate a new tires he had just mounted up and poured a capful of stans into. He spun the tire and we could not figure out what that noise was as the tire rotated. We dismounted the tire and a clump a grey, congealed Stans fell out...