Reviving A Limestone Masterpiece

October 09, 2018 - by commarchtest

Restoration experts joined forces to tackle the intensive task of restoring historic Italian limestone.

The Main Fountain Garden at Longwood sprawls five-acres and was listed on the National Register of Historic Places in 1971. Photo: Courtesy Longwood Gardens By Jennifer Richinelli Enduring harsh Philadelphia winters for close to a century, the stonework comprising the Main Fountain Garden at Longwood Gardens was in desperate need of attention. Many of the limestone pieces were discolored and others required replacement due to the fact they had deteriorated. The Main Fountain Garden at Longwood sprawls five acres and was listed on the National Register of Historic Places in 1971. Inspired by the great water gardens of Europe and the 20th-century technology from the World’s Fairs, it was conceived, designed, and constructed by Pierre S. du Pont, the owner of Longwood Gardens. Architecturally the Main Fountain Garden was influenced by the Italian Renaissance period and features loggias, arches, and decorative sculptures. The fountain is elaborately detailed, with more than 4,000 pieces of ornamental stone fountainheads. Du Pont sought the expertise of artisans at A. Olivotti & Co., Vicenza, Italy, to hand carve each piece. The company also quarried the Bianca Avorio limestone for the project. During a five-year period, from 1931 to 1936, du Pont and A. Olivotti & Co. worked diligently to select and refine designs for the garden’s sculpture collection. According to New York City-based Beyer Blinder Belle (BBB, beyerblinderbelle.com), the architectural firm selected to head the restoration, “decorative stone octagons, basins, urns, sprouts, grotesque masks, and flower bouquets were arranged throughout the garden, creating a rhythmic, classical composition of exquisite detail that further animated the complex hierarchy of fountains.” From the time of its completion in 1936 until du Pont’s death in 1954, the Main Fountain Garden was the center of spectacular fountain shows, which were open to the public. “After 1954, numerous small changes occurred in the Main Fountain Garden, including boxwood replacement following a snowstorm in 1958, and behind-the-scenes maintenance of the fountain systems,” stated a BBB representative. “Some changes were not material, such as the introduction of musical accompaniment and fireworks with the illuminated fountain show.” The design of the Main Fountain Gardens was influenced by the great water gardens of Europe and the 20th-century technology from the World’s Fairs. Photo: Courtesy Longwood Gardens In 1970, a project commenced to extend the wall of the Pump House—a room located under the west portion of the Rectangular Basin that stored the original pumps and electrical equipment. A solid wall of indented arches capped with an open balustrade replaced the original steel-trellis arcade, which featured urns and sleigh fountain basins. The wall terminated in a marble-clad pavilion and formal stair to the Fountain Terrace. A raised plaza was formed to the west, in which a lead-clad circular fountain was located. This was the only basin selected for the Lower and Upper Canals. A restoration architect said that changes in the Main Fountain Garden and fountain shows over time were in keeping with du Pont’s original hope that the garden would be used to its greatest potential to delight and amaze visitors. A team of restoration experts in their respective fields joined efforts to transform the Main Fountain Garden back to its former glory as one of “the most expansive and magnificent groupings of fountains in the U.S.” Accomplishing the feat demanded 25 masons to dismantle 5,312 pieces of stone in 15,033 hours, a 27,304-hour conservation period, and 25,828 hours to reinstall the stone pieces. Additionally, numerous studies and planning meetings were held before the two-year restoration project was set into motion. Longwood Gardens, in partnership with the Longwood Foundation, a separate nonprofit charitable foundation, funded the $90-million revitalization. “Saving and restoring as much of the original stonework was always a priority and an integral part of our stewardship of the Main Fountain Garden,” explained Paul Redman, CEO of Longwood Gardens (longwoodgardens.org) in Philadelphia. “The condition of the stonework had deteriorated in many areas of the garden since it was first installed in 1931. Some areas of the garden were not accessible to guests due to the poor condition of the stonework and resulting safety concerns. For example, the Fountain Terrace was closed off to guests since the 1990s. Repairing, restoring and replacing the stonework was a vital part of the project since day one of the planning process.” After Redman assumed leadership in 2008, a new planning process was instated and by 2010 a physical-site master plan was created by West 8 (west8.com), an urban design and landscape architecture firm based in Rotterdam, NY, along with six other consulting firms. The plan emphasized the revitalization of the Main Fountain Garden as a top priority and was finalized in 2011. The following year, Bancroft Construction Co., Wilmington, DE (bancroftconstruction.com), was asked to coordinate the fountain rebuilding, as the company was already involved in other projects at Longwood. A total of 13 architectural firms were interviewed, and after an extensive three-stage evaluation, New York City-based Beyer Blinder Belle was selected to head the restoration. “The first step was to engage the greatest design team and experts in the world to lead us through the revitalization of the Main Fountain Garden,” said Redman. “Restoring the Main Fountain Garden was a priority, but knowing how to approach and execute a project of its magnitude was beyond our expertise.” Because Longwood Gardens is visited by more than 1.35-million people each year, it was imperative the elected team devote their full attention to the restoration of the Main Fountain Garden. Joining Beyer Blinder Belle (BBB) in the conservation of the stonework was Dan Lepore & Sons, Conshohocken, PA, and Quarra Stone Co., Madison, WI (quarrastone.com). Artisans at A. Olivotti & Company in Vicenza, Italy, skillfully hand carved each intricate piece of the original limestone. Photo: Courtesy Longwood Gardens

Deteriorating Stonework

The historic Italian limestone that forms the Main Fountain Garden was in disrepair, necessitating the closure of parts of the garden, according to BBB representatives. “The stonework in the Main Fountain Garden was suffering from the effects of harsh winters and the constant flow of fountain water. Stonework problems included the extensive growth of moss and algae, erosion of stone surfaces, degradation of mortar joints, surface staining and efflorescence, cracking, inappropriate earlier repairs, and missing stone elements.” “It all needed cleaning and suffered from exposure to the elements over more than 80 years,” Redman said. “Some stone had incorrect repairs done at another point in time that needed to be corrected. In general, there was cracking and crumbling, while some pieces, thankfully, a limited number of them, were beyond repair and needed to be replaced. Others could be repaired or restored, but literally every piece of stone was touched somehow as part of the project in addition to adding new elements to the garden. “We were actively involved in every step of the stone conservation process from beginning to end,” Redman continued. “Every piece of stone was barcoded and tracked so that at any moment we could see where that piece of stone was in the process. Also, we played an important role as the client in reviewing the first prototype carvings of the new floral bouquet fountains. Unfortunately, the originals had deteriorated to such a degree that they could not be saved. The Main Fountain Garden’s bouquets have specific floral themes, and we reviewed every first mock-up to ensure that the new carvings were as close to the original as possible based upon the limited information we had. We met regularly with our project leads and design team to address any issues or questions that arose. It was truly an interactive team effort.” The loggia was among the areas that were in desperate need of cleaning and repair. To achieve the end result, a hydroxylating conversion treatment was applied to all historic stone pieces, which penetrated the stone surface and adhered to mineral grains to bind the stone surface together, increasing its resistance to air pollution, acid rain, and normal weathering. Photo: Courtesy Dan Lepore & Sons


After months of extensive and thorough research, Longwood Gardens, in collaboration with the design team, developed a comprehensive program to restore the elaborate stonework. “Understanding the history and original design intent of the Main Fountain Garden was critical to restoring and reinterpreting the design,” stated the team at BBB. “The most historically significant elements of the Main Fountain Garden, the historic central core, the character-defining decorative stonework and south Pump House wall, warranted a Level 1 restoration treatment as defined by The Secretary of the Interior’s Standards for Preservation (U.S. Department of Interior, Washington, doi.gov). Areas or elements with a lesser degree of historic integrity, or areas that have been significantly compromised, were appropriate for a Level 2 or 3 treatment of rehabilitation or reconstruction. The original elements of the garden were restored, with new interventions marking a subtle shift in material and detail that differentiates from the original. The project achieves a multi-layered reading of the garden that balances the historic and contemporary.” BBB conducted a detailed survey to record the condition of all the stone pieces in the garden. “Each stone was described in photographs and drawings, with specific defects diagnosed and repair methods identified,” stated the firm’s representatives. “The stone-by-stone restoration approach prioritized the retention of historic fabric in order to maintain the authenticity of the garden. However, a small number of stones that were missing, or had become so eroded as to be illegible were replaced. “The extensive excavation across the garden necessitated the careful dismantling of more than 5,000 pieces of carved ornamental limestone,” a BBB spokesman went on to explain. “Each stone was carefully packed into a crate and labeled with a unique code. The dismantled stones were transported 30 miles from Longwood to the workshops of Dan Lepore & Sons in Conshohocken, PA. Over an 18-month period, stones were carefully cleaned, their condition assessed, and almost 3,000 individual stone repairs carried out.” Each stone piece was given an alphanumeric code that corresponded with its location on the site. As each unit was removed, it was numbered with permanent ink on a non-visible face and tagged with a code-stamped aluminum tag. Photo: Courtesy Dan Lepore & Sons

The Conservation Process

Meticulous details and organization played a tremendous role in creating a harmonious workflow that was required for a successful job. “Never had a project this large come into our office,” said Kathryn Biddle, architectural conservator at Dan Lepore & Sons. “I think it’s very unique in that sense. It was really fun that everyone from our shop could come in and see the progress of the work every single day.” Biddle went on to say that while managing the enormous amount of stone pieces was a task in itself, it was also a rewarding experience. “As each stone was removed from its crate, it was numbered with permanent ink on a non-visible face and tagged with a code-stamped aluminum tag. Every crate containing stone was then labeled with a laminated quick-response ‘QR’ code to enable its tracking throughout the duration of the project. The QR code system was capable of identifying, locating, and cataloging all tagged crates by scanning the code attached to each crate. Once unloaded at Lepore’s warehouse, stone cleaning and restoration began.” Every stone component that entered Dan Lepore & Sons’ facility was evaluated on an individual basis. “Limestone varies throughout the world and country, and this stone in particular has a lot of shell inclusions that makes it deteriorate in unique ways,” explained Biddle. “A conditions survey of all 5,373 stone elements was completed based on the architect’s drawings, which included before and after photographs, dimensions, and geospatial location on the site prior to dismantlement.” Biddle worked closely with Miriam Kelly of BBB to restore the limestone pieces. “These are old friends,” Kelly said of the stone statues. “But how do you take care of that old friend and make sure that when they come back to the garden in two years’ time that they meet their old friends again and feel delighted? “We were looking after Pierre du Pont’s real personal vision,” Kelly went on to say. “This is what he chose down to the last detail. We’re unfolding his story again.” Kelly explained that when evaluating the stone pieces there is an entire range of different types of decay. “There are things that have shattered,” she said. “Things that have gotten very cold and wet, and exploded.” “The most rewarding part is to see the stone once it is repaired and cleaned,” said Kathryn Biddle, architectural conservator at Dan Lepore & Sons. “I don’t think anyone imagined that they would get this clean or that you would be able to see this much detail on them.” Photo: Courtesy Dan Lepore & Sons

Cleaning and repairing

Stone repair methods included cementitious patching, grouted crack repairs, pinned crack repairs, stone Dutchmen, and full stone replacements. BBB personnel explained that the first step in the cleaning process was vacuuming and brushing dry stone to remove loose salts and biological deposits. “This was followed by two cycles of gentle pressure washing, after which stones were misted with clean water and gently scrubbed to remove deeply ingrained deposits,” stated the firm. “A gentle micro-abrasive cleaning system, which projects a swirl of air, water, and a fine powder under low pressure along the stone surface was used to remove heavier deposits. A biodegradable biocide was used to remove residual biological growth and staining from air pollution.” A hydroxylating conversion treatment was applied to all historic stone pieces. The open-grained surface of the Italian limestone had deteriorated, causing the stone surface to crumble. The treatment penetrated the stone surface and adhered to mineral grains to bind the stone surface together, increasing its resistance to air pollution, acid rain, and normal weathering, according to the team at BBB. Additionally, the treatment primed the stone for the application of an ethyl silicate/silane water repellent after stones were reinstalled. For small areas of stone loss, mortar patches were used for repairs. “This technique involved the careful removal of decayed stone and application of a vapor-permeable cementitious patching mortar, color-matched to the surrounding stone,” explained the team from BBB. “The patch repair was built-up in layers onto stone that is wetted to help the repair mortar adhere. The surface of the repair was then shaped and tooled so that it matches the profile and texture of the host stone. Color-matching patch repairs required a wide selection of mortar colors to reflect the color variations in the natural limestone.” In larger areas where stone loss was apparent, as well as areas in direct contact with water, Dutchman repairs were used. The process involved removal of decayed stone and the installation of a piece of matching stone that was cut, carved, and tooled to blend with the host stone. “The Dutchman stone had almost identical petrographic characteristics to the host stone so that it could absorb and evolve water at the same rate,” explained the BBB team. “Dutchman repairs were anchored with stainless-steel dowels set in epoxy adhesive and finished with a very fine 1/32-in.-wide grouted joint. In time, Dutchman repairs will weather and blend visually with the historic stone in the garden.” Dan Lepore & Sons partnered with stone carvers from around the country, including Quarra Stone in Madison, WI, to hand carve the limestone and replicate exact details of the original stone. Fortunately, new limestone was sourced from the original quarry in Italy, so it was a perfect match to the historic stone. As Redman explained, the garden’s 75 floral-bouquet fountains had eroded and their delicate carving was no longer legible. “Using historic photos, the original flower motifs were identified and the stone carvers produced replacement bouquets using combinations of flower motifs,” the team at BBB stated. “Each bouquet is hand carved and unique.” Historic photographs were also used to develop designs for replacement fountain basins at the Turtle Pool, which were missing. Each basin needed to be water-tested to finesse the flow of water at the basin lip. The new fountain basins were first cut roughly on a cutting machine before the carved detail was added by hand. Moreover, only one of the original four turtle statues from the Turtle Pool survived, the turtle was scanned in 3D and a template was made from which replicas were carved. “By the project’s end, nearly 3,000 individual stone repairs had been performed,” said Biddle. “Once repairs were completed and approved, the stones were re-crated and returned to the jobsite for final installation. All the stone elements were reinstalled using a lime mortar.” The lime mortar was colored to match the limestone, and stainless-steel anchors and pins were used to secure the stones back to the concrete substructure. “The most rewarding part is to see the stone once it is repaired and cleaned,” said Biddle. “I don’t think anyone imagined that they would get this clean or that you would be able to see this much detail on them, which was really unrecognizable before, when they were on site. “The amount of thought and care that was put into creating these fountains is really awesome to see,” Biddle went on to say. “It’s really nice to kind of feel like I’m [Pierre du Pont] when I’m recreating pieces of stone and evaluating everything. It’s just really nice to have that connection to the past.” Redman shared Biddle’s sentiments on the completed restoration of the Main Fountain Garden. “The project had many exciting challenges,” he said. “We had to work through fundamental philosophies to guide the project by balancing legacy with forward-thinking innovation, as well as making the financial commitment to invest in the project to ensure that the mechanical systems and infrastructure achieved our long-term reliability and sustainability goals.” In the end, the efforts were worth it. “Our guests’ reactions have exceeded our expectations,” said Redman. “The garden is more welcoming and accessible for guests to explore. Architectural lighting has made it a daytime and evening destination for our guests. New features, such as the Grotto, Pumphouse Plaza, and Historic Pump Room and Gallery are enticing visitors to linger and explore. Obviously, the fountain performances are dazzling guests. Our first season was planned to go from May to September, but we extended the fountain season through October due to guest demand. We welcomed more than 600,000 guests during the inaugural season.” Reprinted with permission, Building Stone magazine, Spring 2018. Visit Longwood Gardens.

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