MARIETTA, Ga. (Oct. 23)—Columbian Chemicals Co. will temporarily cease production at its El Dorado, Ark., carbon black plant effective Nov. 30, resulting in the loss of 50 jobs. In an unrelated move, the company will consolidate its four North American customer service functions into the firm's Marietta operation, beginning Jan. 1. Manuel J. Iraola, chairman and president of the company, cited overcapacity as the prime reason for Columbian's eroding profitability and the temporary closure of the El Dorado site. Overcapacity in North America has eroded the firm's profitability, which "is undermining our ability to support the capital requirements of our plants, to upgrade our environmental processes and to provide a reasonable rate of return to our shareholders by earning more than our cost of capital," he said. As for the customer service consolidation, it has nothing to do with the El Dorado closure, a Columbian spokesman said. "Temporarily closing the El Dorado plant is an economic move. Closing the sales offices will provide our customers with a higher level of service and quicker response," he said.