Abstract: A room temperature vulcanizable composition which is stable under anhydrous conditions, but when exposed to atmospheric moisture cures to an elastomeric solid comprising (1) a hydrocarbonoxy terminated linear organopolysiloxane containing at least two hydrocarbonoxy groups per molecule, (2) an organo-silicon compound or partial hydrolyzates thereof containing at least two hydrocarbonoxy groups, (3) a titanium ester or partial hydrolyzates thereof, in which the hydrocarbonoxy groups linked to the organopolysiloxane (1), organosilicon compound (2) and titanium ester (3) are the same, and (4) carbon black which has been intimately combined with or treated with a hydrophobic agent to impart hydrophobic properties thereto, in which the hydrophobic agent is inert to the hydrocarbonoxy groups linked to the organopolysiloxane (1), organosilicon compound (2) and titanium ester (3).