JAIC 1997, Volume 36, Number 2, Article 4 (pp. 143 to 150)
JAIC online
Journal of the American Institute for Conservation
JAIC 1997, Volume 36, Number 2, Article 4 (pp. 143 to 150)

A NEW TECHNIQUE FOR DETERMINING THE DEPTH OF PENETRATION OF CONSOLIDANTS INTO LIMESTONE USING IODINE VAPOR

RAKESH KUMAR, & WILLIAM S. GINELL



3 METHOD


3.1 CONSOLIDATION TREATMENT

Samples of both limestones, in the form of 5 cm cubes, were immersed in the respective solutions of the consolidants to a depth of 5 mm and were impregnated by capillary rise. After 10 minutes of impregnation, samples were removed and allowed to cure at room temperature for 15 days. All consolidants mentioned above were applied on Indiana limestone. Only a limited number, however, were tested on the Xunantunich limestone.


3.2 DETERMINATION OF PENETRATION DEPTH

After the solvents had evaporated and the consolidants had cured, samples were sectioned parallel to the direction of capillary rise and placed on a perforated Teflon base in a glass chamber within a fume hood. All samples were arranged in such a manner that the freshly cut surfaces could be observed from outside the chamber. Iodine crystals were then carefully placed at the bottom of the glass chamber. The chamber was closed tightly with a glass lid to avoid iodine vapor loss. Samples were exposed in the iodine vapor-filled chamber for about 5–10 minutes. A yellow color started to appear on some samples within 2–5 minutes. Samples were then removed from the chamber, and the penetration depths corresponding to the colored areas were evaluated.

In separate tests, cured consolidant films, limestone dust, and both consolidated and unconsolidated limestone were exposed separately to iodine vapor, and it was found that only the consolidant films and the consolidant-treated stone developed color.

It is important to note here that exposure time should be slightly longer for some consolidant concentrations. If a consolidant is not completely cured when the test is performed, it is possible that the yellow color may persist for a longer period. However, after a longer exposure to an open-air environment, the color will eventually disappear. If the iodine treatment is performed before solvent evaporation is complete, iodine reaction with the solvent may occur and the solvent penetration depth, rather than that of the consolidant, may be indicated.


Copyright 1997 American Institute for Conservation of Historic and Artistic Works