Bringing the beauty back
Rehabs and restorations case study
The Kenan family heritage dates back to the earliest founders of North Carolina, with the family name being synonymous with prestige and philanthropy.
When Graham Kenan unexpectedly passed away at age 38, he was working at his law office in New York City. His death was attributed to a second wave of the devastating 1918 flu epidemic. His condition slowly worsened, which allowed him enough time to overview and modify his will, providing great details in many respects. Yet, upon combing through the family archives in Chapel Hill, N.C., and reading his entire will, no mention is made of his future burial and memorial desires.
Situated along the wooded, quiet perimeter of Oakdale Cemetery in Wilmington, N.C., the Graham Kenan Mausoleum calls out like a sentinel in time. Its bright white Vermont marble shines through the trees like a beacon to visitors. However, only two people are entombed inside, Graham Kenan and his wife, Sarah, who outlived her husband by nearly 50 years.
Not a single marking or attribution is visible on the structure’s exterior identifying the architect or builder. To find out more about the mausoleum, The Vermont Marble Co. ran a one-page promotional in two separate publications, American Stone Trade, March 1923, and Park & Cemetery & Landscape Gardening, May, 1923.
The Kenan Mausoleum was designed by the Carrere & Hastings Co. of New York City. – architects who had been awarded the contract to build the New York Public Library in 1895. This was, possibly, the first company to adopt the transformative curtain wall construction technique, which employed a hidden internal steel framework and an outer façade of stone. Therefore, most of the structures the firm built looked like solid stone and were classical in nature, however were more modern under their outer skin veneers.
All indications are that the Kenan Mausoleum is constructed of solid masonry, from blocks of white Vermont marble, but that hasn’t been verified through a blueprint or construction records.
The structure was erected by one of the premier monumental builders of the early-1900s, the Presbrey-Leland Co. of Valhalla, N.Y., which constructs monuments still today. The large marble blocks are mated perfectly, with butter-knife-thick joints. Considering 90 years have passed since its construction, the building is in good condition. Unfortunately, the hard white mortar used in the narrow joints allowed for little or no movement from expansion and contraction, due to changes in temperature and moisture levels.
Because of this unforgiving mortar, the marble has developed many hairline cracks, radiating from the mortar joints, outward. This also is visible in the frieze portion of the entablature, and along the lowest horizontal mortar joint, where the wall meets the front stairs. There, cracking and spalling have chipped away stone slowly for many decades.
Many of the repaired areas had cracked and failed, yet again. Non-cement-based repair materials also tend to attract staining on the surrounding marble, which was visible along assorted mortar joints throughout the structure.
Although mortars and re-pointing may seem a simple and straightforward subject, untold damage has been done to numerous structures by careless and misguided mortar removal and poor mortar selection. As a rule of thumb, when re-pointing historic structures, the mortar should always be considered as a sacrificial material. In other words, the mortar must be more forgiving and softer then the substrate – in this case, slightly weathered marble.
If the mortar on a historic structure has performed well but is failing due to age, it should be replicated by doing mortar testing of some kind, such as acid digestion or petrographic analysis. In this case, the original outer pointing mortar was far too hard; therefore, it can be assumed it is very high in white Portland cement. It was not desirable to imitate it.
No cracking or loss was found in large portions of the mortar joints. It was decided that a minimum level of intervention was the safest option.
All previously repaired joints, and all cracked and all open mortar joints, were carefully hand chiseled and raked out. All lose mortar was removed. This is a time-consuming process, as great harm can be done to the marble along the joints, during the mortar removal process.
Although a mortar joint may have been cracked or open on one side, it still was often fully adhered on the opposite side, making the mortar removal a delicate task in the narrow joints, found throughout the walls of this marble structure.
There are three versions of NHL mortars, varying in both hardness and setting time. The softest and slowest to set is the 2.0, followed by the 3.5, with the fastest and hardest setting being the 5.0. The repair and pointing mortar was formulated with one part 3.5 NHL to 2.5 parts fine white crushed marble.
Biological staining is the largest cause of discoloration and soiling in most rural settings and in cemeteries, in general. In order for the biological activity to be killed off completely for any length of time, it must be eliminated down to its roots.
D2 biological stone cleaner was applied to the stone when dry, to permeate deeply into the pores of the stone. Light hand scrubbing was performed on all highly stained areas to detach biological growth. A second application of D2 stone cleaner was performed on all severely stained areas. The entire structure was then low-pressure rinsed with clean water.
The D2 will have a delayed affect and, over the course of a few weeks, the biological activity will die off, and the stone will become much cleaner. Marble is composed, primarily, of calcium carbonate, which does not benefit from most types of chemical treatments. Most coatings can and will trap moisture, which can do more harm than good on nearly all historic exterior masonry.
Conservare Hydroxylating Conversion Treatment (HCT) is made by Prosoco. It was applied to the entire structure in multiple coats, followed by the associated finishing rinse. It is a two-component, waterborne treatment that protects and strengthens deteriorating carbonate building stones such as marble and limestone, by forming a stable, well-adhered, conversion layer on carbonate mineral grains.
The entire structure was then also treated with Cathedral Stone Products’ breathable Water Repellent, R-97, which does not block the pores of the stone, permitting essential vapor transmission. Additionally, the bronze on the front door and read window frame and grating that had caused long-term staining through copper leaching was cleaned with a product called Chromglanz. The bronze was then masked off, and multiple applications of the solvent-based Incralac were applied.
Originally published in Masonry magazine.
About the Author
Jonathan Appell is a gravestone conservator and preservation mason who delivers gravestone conservation training workshops and stone preservation projects throughout the United States. Contact him at 860-558-2785 or firstname.lastname@example.org, or visit www.gravestoneconservation.com.