Success is brewing for Thomas Kemper sodas. (Thomas Kemper Soda Co., brewer of root beer in Seattle, Washington)

Back in the land of gourmet coffee lovers, another upscale specialty beverage is brewing - Seattle's Thomas Kemper root beer. Laura Bracken, president of Thomas Kemper Soda Co., projects 1993 sales of $2 million, a 100 percent increase from last year.

Kemper root beer is bucking a category trend. As of April 1993, total volume sales of root beer were down 1.8 percent at $29.1 million versus a year ago, reports Information Resources Inc., Chicago.

Unlike most carbonated soft drinks, Kemper's products are brewed at Thomas Kemper Brewery in Poulsbo, Wash. The root beer first w;is produced as an experiment in October 1990.

Kemper uses honey as its primary sweetener. The product contains only one-tenth of I percent of the preservative sodium benzoate for stability. It's brewed in batches of 500 gallons of water with about a dozen ingredients, including sassafras bark extracts and oil of …