By Ernest Scheyder NEW YORK, Jan 21 (Reuters) - Coatings and chemicals maker PPG Industries Inc said on Thursday its fourth-quarter net income doubled as costs fell and profits from affiliates increased. The company said industrial demand is gradually improving -- mostly in Asia -- and that it is "guardedly optimistic" about 2010 opportunities. Nevertheless, shares fell 3.6 percent in early trading. For the fourth quarter, the company posted profit of $142 million, or 85 cents per share, compared with 43 cents per share, or $71 million, in the year-ago period. Excluding an asbestos-settlement fee, the company posted earnings of 86 cents per share. By that measure, analysts had expected earnings of 73 cents per share, according to Thomson Reuters I/B/E/S estimates. Revenue slipped 2.3 percent to $3.12 billion from $3.19 billion. Analysts had expected revenue of $3.04 billion. PPG, which gets the bulk of its revenue from paints used for buildings and boats, cut its cost of sales by 4.7 percent during the period. Additionally, income from noncontrolling stakes in several ventures, together with asset sales, jumped to $52 million. PPG also cut its short-term debt and its current portion of long-term debt by 70 percent and bolstered its cash on hand above $1 billion.