5 SUMMARY OF MATERIALS AND FABRICATION TECHNIQUES

The Glass Flowers are made of a binary alkali glass. The models were made by the glass technique known as “lampworking,” in which the glass is heated in a flame until it becomes soft and malleable and then pulled and twisted into shape with pincers, tweezers, and other tools. Between 1886 and 1895, the color was achieved by cold-painting the cooled surface of the glass with paint made with a variety of media (dammar, hide glue, and gum arabic were identified), using pigments readily available at the time.

Beginning in 1895, Rudolph Blaschka experimented with colored glass and with enameling on top of the clear glass substrate. He noted many technical difficulties with this process, including alterations in color from reheating and an inability to anneal the glass shapes properly after enameling. Analysis indicated that the enamel is made of lead glass, which would melt at a lower temperature than the soda glass substrate. The amount of lead oxide in the composition of the enamel varied widely, suggesting Rudolph's experimentation. In this period, varnishes were used to make the glossy surface of the enameled glass more matte. Occasionally, Rudolph also painted the enameled models if he was not satisfied with the color.

The Blaschkas employed a wide variety of fabrication techniques, relying on their understanding of glass combined with their creativity. In some of the larger models, wires were inserted into tubes of glass to make stems, and then the tubes were heated so that they softened and flattened. Leaves and petals were made separately, sometimes attached by wire, glue, or both. The early models were cold-painted; the later models were enameled and varnished to achieve the appropriate surface and then assembled. The smaller sections and enlarged details were made in a similar manner. The sections are made of flat sheets of glass that were cut; seeds and pods were attached with hide glue.

The delicacy and ingenuity of Leopold and Rudolph Blaschka's work is more apparent the more one studies the models. The range of fabrication techniques they used reflects the variety of flora they imitated, from small wildflowers to orchids to banana leaves.

ACKNOWLEDGEMENTS

ACKNOWLEDGMENTS The authors would like to thank Henry Lie, director of the Center for Conservation and Technical Studies, Harvard University Art Museums, for his support throughout the project. We thank Eugene Farrell, senior conservation scientist, and Amy Snodgrass, assistant conservation scientist, for their assistance with the analysis. We would also like to thank Susan Rossi-Wilcox of the Botanical Museum for instigating the study.