Earthen Architecture Initiative_Assessment of Ethyl Silicate Consolidants for Earthen Finishes_GCI

Earthen Architecture Initiative_Getty Conservation Institute

Assessment of Ethyl Silicate Consolidants for Earthen Finishes

Earthen finishes, found as decorative or protective coatings on architectural surfaces, have been the subject of conservation treatments due to their vulnerability and aesthetic or cultural significance. Consolidation, or the re-establishment of grain-to-grain cohesion, is performed in response to disaggregation which can be disfiguring or destructive to the finishes.

Consolidation treatments for earthen materials began to be used in the 1960s and 1970s. Since this time, ethyl silicates have emerged as a popular but not fully understood treatment. However, despite decades of use of ethyl silicates, it is still unclear how factors such as the composition of earthen materials, their conditions, the consolidant composition, application methodology, or environmental conditions affect the performance of the treated finishes.

The Getty Conservation Institute in collaboration with the Architectural Conservation Laboratory (ACL) of the University of Pennsylvania (UPenn) is assessing ethyl silicate-based consolidants and their effect on various clay-based surface finishes. Ultimately this research aims to provide information to conservators on which ethyl silicates are most appropriate for use with specific earthen finishes and under which conditions they can optimally be used.

 

 

A linear variable differential transmitter measuring the changing height of a treated earthen sample during exposure to fluctuating relative humidity. Photo: Amila Ferron, GCI

Research Program

Investigation at the ACL/UPenn has explored the behavior of earthen finishes after consolidation with proprietary ethyl silicate-based products when exposed to water in both liquid and vapor form. Results have revealed differences in the performance of the ethyl silicates in terms of curing time, expansion and contraction, water repellency, and durability during wet-dry cycling. These differences indicate that the type of ethyl silicate used needs to be considered carefully before administering treatment and that the composition of the treatment material plays an important role in its performance.  

Observation with environmental scanning electron microscopy shows the movement of treated earthen finish materials under conditions of fluctuating relative humidity. In this image, a treated earthen wash is viewed at high magnification. Cracks visible here were seen expanding and contracting as the relative humidity was raised and lowered. Photo: Eric Doehne, GCI

Research at the Getty Conservation Institute is evaluating the behavior of formulated clay-based finish materials when treated with a selection of popular commercial consolidants. Treated materials will be evaluated for appearance, mechanical properties, plasticity, response to water and environmental durability. Two clay types will be used for sample preparation so their effect on the performance of ethyl silicate-based consolidants may be assessed. A preliminary testing program outlines the research methodology. Testing will be carried out in the building materials research laboratories at the GCI.