Riverside Church
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Exterior limestone conservation

ICR developed a conservation program to address the issues of the limestone decay at the tower.

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Exterior Limestone Conservation
• Preliminary conditions survey
• Design & execution of laboratory & in-situ testing programs
• Identification & definition of methods of treatment for cracking, loss and
   disaggregation
• Development of consolidation and repair methods

ICR was tasked with diagnosing the cause of cracking, disaggregation and loss of the statuary and other carved gothic elements on the Indiana Limestone façade of the Church. The work involved a preliminary conditions survey and extensive laboratory work to identify the mechanisms causing decay. The decay appeared to manifest in similar conditions across all elements resulting in cracks, disaggregation and loss.

Laboratory work included visual microscopic analysis, microchemical spot testing, petrographic analysis, Fourier transform infrared spectroscopy, gas chromatography mass spectroscopy, anion analysis, X-Ray diffraction analysis, scanning  electron microscopy, and energy dispersive X-ray spectroscopy. Proposed consolidation treatments were pre-tested in the ICR laboratory for acid resistance and strength increases before site testing. Site tests were evaluated for depth of penetration and hydrophobicity.

The severity of decay and the potential loss in some of the protruding architectural elements posing a possible public threat could not be treated with consolidation alone. ICR had to determine what conditions would be appropriate for consolidation alone and what severe conditions would require removal of decayed material, followed by tooling to sound material, and subsequent consolidation. Due to the great height in many of the decaying elements, the removal of decayed material does not alter the tower's appearance and replacement materials did not have to be introduced.