Track 3: Conservation of modern and post-modern heritage
APT Student Scholar Abstract and Application
Like other older American cities, New Orleans has always had a well-established building tradition, drawing upon the local environment and immediate resources for its building materials. This is especially true for brickmaking in and around New Orleans, which was reliant upon two principle areas of clay extraction: the Mississippi River and Lake Pontchartrain. Mississippi River brick clay has a deep red color, and the bricks made from this material tended to be soft and of poor quality. On the other hand, lake bricks tended to be stronger and uniform in shape and density. Both brick types were used in buildings extensively throughout southern Louisiana in the nineteenth century, although “soft reds” tended to occur more in Antebellum buildings. Likewise, advances in brickmaking technology would have created further variation among brick types by the latter part of the nineteenth century.
These trends in building material are not extensively documented, and the contrasts between their physical characteristics pose a problem for conservators. Naturally, age would be the defining characteristic in guiding conservators on how to monitor deterioration within single brick units. Older bricks tend to be more weathered than newer bricks if exposed to uniform conditions. However, the variation in composition and production between soft red and hard tan bricks calls for assessment of how brick composition relates to physical behavior. This project incorporates methods of physical characterization and performance testing to explain the differences in composition among both soft reds and hard tan brick types, demonstrating how the relationship between physical characterization and performance testing can predict future vulnerability.
This project tests two groups of seven samples that constitute representative examples of typical nineteenth-century soft red and hard tan bricks. Bricks used in this study originated from the Academy of Sacred Heart, Hermann Grima House, Willow Grove Plantation House, Metairie Cemetery, Carrollton Cemetery, St. Louis Cemetery No. 1, and a former 1830s Cotton warehouse in New Orleans’ Central Business District. The methods for predicting vulnerability of soft reds and hard tans essentially has two parts. The first part requires a detailed analysis of two groups of both brick types using polarized light microscopy. This identifies specific mineralogical variation among the soft reds and hard tans. The second part uses weathering and mechanical tests to evaluate and compare each brick’s performance and deterioration rates. In accordance with ASTM standards, water absorption and desorption, accelerated weathering through efflorescence, and modulus of rupture are applied to two groups of fourteen samples to determine general trends in flexural strength, porosity, and salt crystallization. As this project will demonstrate, the results from this testing program will inform a provisional index of vulnerability for future conservators.