7 DISCUSSION AND CONCLUSIONS

Compared to the other possible methods described, the iodine vapor technique seems to be superior in practical use for determining depth of penetration of a consolidant into porous stone. The test can be performed easily in the laboratory or in the field, and it seems to be effective for a variety of consolidants currently used in the conservation of stone. For maximum effectiveness, the stone to be tested should be light in color, and the consolidant concentration in the stone should be at least 1% by weight.

Investigation has shown that the intensity of color is dependent, qualitatively, on the concentration of the consolidant in stone, as well as the depth of penetration, and therefore the distribution of the consolidant in the stone can be determined by the iodine vapor technique. It may also be used for estimating the distribution of a consolidant in stone after aging in the natural environment by using an unaged reference distribution pattern of that consolidant (Kumar and Ginell 1995). This application may be very important for assessing the long-term effectiveness of any consolidant. Finally, as the iodine vapor technique does not require sophisticated instrumentation, it is an economical test procedure that can be used by most conservators.

The experimental observations reported here reveal that the iodine vapor technique is rapid, simple to use, reliable, inexpensive, and more accurate for determining consolidant penetration depth and distribution in stone than methods currently in use.

ACKNOWLEDGEMENTS

The authors would like to acknowledge with gratitude the assistance of Eric Doehne for ESEM studies and Luiz Souza, Mary Striegel, Michele Derrick, and Charles Selwitz for their helpful advice.