NCPTT | National Center for Preservation Technology and Training

Improved Method for Repairing Wooden Structural Beams in CCC NHL District (2011-10)

On December 31, 2011 By Sean Clifford

Development of a Micro-fading Tester with Near-UV Capability (2011-09)

On December 31, 2011 By Derek Linn

Controlling Salt Damage (2011-02)

On December 31, 2011 By Sean Clifford

Figure 2. This photo shows 5 samples of Cordova Cream limestone treated with amounts of PAA increasing from zero at the left to a layer about 10 nm thick at the right. The stones are standing in a bath of sodium sulfate, and were exposed to 39% RH for about 5 weeks.

Growth of salt crystals within the pores of stone can cause serious damage. Salt may enter with ground water or be created by reaction of the minerals in the stone with atmospheric pollutants. As water evaporates from the pores of the stone, the salt concentration rises and the crystals grow until they approach the pore walls. If the salt came into direct contact with the stone, then growth would stop and there would be no stress. However, in most cases there is a repulsive force between the salt and mineral surfaces, so that they do not touch; instead, the salt remains surrounded by film of solution that encourages it to grow and exert pressure on the pore walls. The goal of this study was to develop a chemical treatment for limestone that would eliminate the repulsion, and thereby prevent salt from applying pressure on the pore walls. On the basis of screening tests, the polymer chosen for testing was polyacrylic acid with low molecular weight (~5000). Potassium hydroxide is used to raise the pH of the polymer solution to 7-8, and the solution is equilibrated with calcium carbonate before being introduced into the stone, where the polymer adsorbs on the pore walls. When crystals of sodium sulfate are induced to grow within the stone, the damage is strongly reduced by the coating in most cases. To date, there are problems of reproducibility with the treatment that are not fully understood. Possible explanations are discussed and additional research directions are proposed.

Development of Ceramic Reference Materials for Calibration and Quantification of Portable XRF Data (2011-06)

On December 31, 2011 By NCPTT

A Polymeric Treatment for Controlling Salt Damage to Stone and Brick (2011-07)

On December 31, 2011 By Derek Linn

Call for Abstracts Extended: High-Tech Heritage

On December 19, 2011 By Ed FitzGerald

Mourning Glory: Preserving Historic Cemeteries (2011-11)

On December 13, 2011 By Debbie Smith

APT offering research travel program to Cuba in 2012

On December 12, 2011 By Ed FitzGerald

Scholarships Available for 2012 Iron & Steel Preservation Conference

On December 12, 2011 By Ed FitzGerald

Webinar: Preparing for the Next Disaster

Go Digital and Social: the Public Face of NPS Park Cultural Landscapes Program

Training in Climate Change and Cultural Resources

New Guidance for Installing Solar Panels on Historic Properties

Web Catalog Increases Access to NPS Museum Collections

Archeology & Collections

Architecture & Engineering

Historic Landscapes

Materials Conservation