The Log... ical Solution!

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CCI Newsletter, No. 23, June 1999

The Log... ical Solution!

by David Grattan, Manager, Conservation Processes and Materials Research, and Malcolm Bilz, Senior Assistant Conservation Scientist, Conservation Processes and Materials Research

A partially exposed fossilized log was found in the Hagerman Fossil Beds in Idaho in 1993. The United States National Park Service (USNPS) removed a section of it (about 2.5 m long by almost 0.5 m in diameter) and stored it until 1998, when it was delivered by truck to CCI. But a 3-million-year-old fossilized log does not look quite like the logs you burn in your fireplace! So it seemed logical to do a little scientific investigative work before attempting conservation treatment.

Analysis of the ash content of the log (using ASTM Standard Test Method D 1102-84) disclosed that it is about 95% mineral, indicating that it is highly petrified. Visual examination revealed what appeared to be three main components associated with the log: a yellow material with a slight pattern similar to the grain of wood; a brown sand matrix with a uniform featureless texture; and a similarly featureless yellowish sand. Samples of all three components were subjected to X-ray diffraction, scanning electron microscope elemental analysis, and Fourier transform infrared spectroscopy. Results of these tests showed that all three materials contain a lot of silicon. The yellow material has the highest iron content and appears to be a clay; the yellowish and brown sand both appear to be quartz. The elemental composition of the yellowish sand is intermediate between the yellow material and the brown sand, suggesting that this is not a third distinct material but rather a mixture of small pieces of petrified log and the brown sand matrix.

Armed with the results of these scientific analyses, we can now proceed with conservation treatment. In the coming months we will attempt to remove the sand matrix and isolate the petrified wood fragments. If necessary, some log fragments can then be consolidated. Preliminary tests have indicated that Rhoplex AC-33, an acrylic emulsion, may be suitable for this purpose.

Thanks to the combination of science and conservation, when the log is returned to the USNPS some segments should be suitable for display.