“The Use of Ultrasonic Cleaners for the Removal of Scale Deposits from a Terra Cotta and Limestone Fountain”

Cuba ’98: IVth International Conference on the Rehabilitation of Building and Architectural Heritage.

Author and Speaker: Joseph Sembrat

ABSTRACT

Nearly 60 years of hard water and corroding iron pipes almost completely obscured the fine detail work found in Christian Petersen’s “Four Season’s Fountain” located in front of the Memorial Union on Iowa State University’s campus. Iron stains and scale deposits of secondary calcium carbonate measuring up to 1/2″ in some areas covered nearly all of the terra cotta panels and the four carved limestone sculptures. Misguided previous attempts to remove the deposits using sand blasting and hydrochloric acid were unsuccessful and even damaged sections of the fountain.

A system designed and built by the author which utilized a proprietary 40 KHZ ultrasonic cleaning  generator and associated piezoelectric transducer elements were successful in removing both the rust stains and the scale deposits without any noticeable changes in the surfaces of the terra cotta.

To prevent the reoccurrence of the iron staining all iron pipes found in the recirculation portion of the fountain were replaced with 304 stainless steel. A water softening and particulate filtration system were used to combat the water hardness problem.