Client: International Conservation Services

Location/Site: Duntroon House, Canberra ACT

Project: Basement desalination of brick and stone walls

Scope of Works: Let’s Clean was asked to desalinate in a basement at heritage-listed Duntroon House where salts had accumulated. The basement opens into a roughly square room of brick and mortar covered with render. This then passes through a small passage to a long room of stone and mortar covered with render. The render was partially removed by a third party in areas of obvious degradation to allow us surface contact for the desalination process.

Method: Using the Captive Head Washing technique via our BlueVac System, Let’s Clean performed salt extraction on all applicable stone and brick surfaces on the basement level. We completed three passes, where each pass means passing the Captive Head over a given area once.

The Captive Head uses low pressure water to dissolve surface salts and simultaneously removes these dissolved salts by vacuum to a capture tank. Water samples were obtained from the capture tank and had their salt level measured by testing for conductivity. Approximately half-square-metre (0.5 m2) sections of the square and the long rooms were designated as sampling areas, allowing us to measure the change in surface salts after each pass.

We first removed loose material with a nylon brush prior to performing salt extraction. After this, we used the BlueVac System to extract salts from the surface. The general time frame we worked with for this project:

• Perform the first pass, then wait one day.

• Perform the second pass, then wait at least one day.

• Perform the third pass.

The waiting period between passes is to allow salts to migrate towards the surface, where each salt extraction pass effects a reduction in salts contained within the masonry.

Outcome: A downward trend is the ultimate goal of masonry desalination and we were pleased with the overall reduction in salts obtained from samples during desalination work at Duntroon House.