The USS Maine National Monument Restoration Project
The USS Maine Monument is significant not just for it’s historic statement, but because it is a masterwork completed by master sculptor Attilio Piccirilli, who, along with his brothers, are responsible for some of America's most iconic marble sculptures, including the lions at the New York Public Library and Washington D.C.’s Lincoln Memorial.
Additionally this monument is at one of the two main entrances to the park, which recieves 37.5 million visitors a year, and has become an iconic and familiar meeting place and location for activism. Because of the Maine’s cultural iand historic importance, laser removal represented the most effective way to ablate hard to remove biological growth while preventing damage to the soft marble, allowing park visitors and patrons to enjoy the sculpture.
Location:
Central Park South West corner, New York City, NY
Issues:
Degraded mortar joints on monument base
Severe staining on Tennessee Pink Marble figurative sculptures
Unstable cracks and areas of loss on both granite and marble sections.
Treatment Carried Out:
Wet cleaning of granite base
Raking and repointing with custom latex reinforced mortar mix
Wet cleaning of soft Tennesee Pink Marble sculptural elements
Masonry repair of deep cracks
Laser cleaning of the Atlantic figurative sculpture on the East side of the monument
The Pointing of the granite base-
Pointing refers to the sacrificial layer of mortar filling the joints between blocks of stone or concrete. Pointing mortar is not meant to hold stones together, but rather keep them from shifting too much and provide a weaker, more flexible material to absorb the energy from expansion and contraction patterns, breaking and cracking instead of the stone. Pointing mortar should also be more porous and allow a channel for water and minerals to leech through instead of the stone, providing a path of least resistance. For the U.S.S. Maine, we used a special formula from Edison Coatings that was color matched to the stone, and instead of water, we made our mix with RL ice-9 latex additive, which increases the salt-scaling, freeze-thaw resistance and thus, the lifespan of the mortar.
To begin, we had to remove any remaining old mortar which was cracked and dirty using hand chisels, angle grinders, and an arbortech dual blade mortar saw. We then pressure washed the monument, taking special care to clean out the joints to be filled. We spent nearly three weeks refilling the mortar joints between the stones to create a solid, cohesive surface. Repointing involves carefully inserting the mortar with appropriate sized pointing irons and compressing it to create a strong, solid material while being careful not to stain the surface of the granite with excess mortar.
Laser biofilm removal-
Another major aspect of the U.S.S. Maine National Monument restoration project is the application of GC Lasers 100i laser cleaning system to remove stubborn biological encrustations that have grown on the surface. The biological staining resists typical rinsing methods. Laser cleaning allows controlled and effective surface cleaning without the dangers of harming the material introduced by harsh solvents and/or excessive water pressure. Previous steam cleaning treatments had exhibited some light abrasive damage if the pressure was too high. Unfortunately the biofilm was more robust than the soft Tennessee Marble, which although a marble in name is more accurately described as a soft limestone. Thus the senior conservator at Central Park Conservancy decided that targeted laser cleaning would be the best approach for the safety of the object
Because the GC Lasers 100i laser cleaning system is highly tunable, finding the correct setting required a little finesse (evidence of testing in fig. 4) Once the laser settings are dialed in for the specific application, the laser is moved around the surface to ablate the biofilm away.
As one of the two post-graduate interns, I was tasked with some project management responsibilities. One of my tasks was designing a cover system using tarps and a pop-up tent to cover the working area to make sure there was absolutely no potential for the public to view the working end of the lase. To make the process more comfortable for the hot weather I also included portable fans in my design.
Masonry Repairs-
Along with this, we added a custom masonry repair mortar (Edison Coatings Custom 45) to losses throughout the sculptural elements of the monument (fig. 8-10). The visual crispness of the carved forms have softened over time due to natural weathering processes, exposure to acidic atmospheric pollutants, and biological staining.
This project was highly collaborative, and each team member had a hand in each step of the treatment. Being a part of such a cohesive team was a joy and a privilege.
Figure 9- My colleague Emily filling in some of the larger areas of loss along old cracks.
Figure. 2- The team working to repoint the base.
Figure 4- Testing out laser cleaning methodologies on an inconspicuous area to dial in the most efficient settings. The use of sprayed deionized water greatly improved the end result, as shown in the patch here.
Figure 5- The complex shape and scale of the Atlantic figure meant getting creative with the cleaning position of the handheld laser operator, here I am using my whole body to get to a difficult to reach spot.
Figure 7- The Atlantic figure during treatment. We masked off a square before treatment using blue painters tape to illustrate the contrast for the documentation process.
Figure 10- The same area as fig. 8, after treatment.
Figure. 1- Repointing with custom mortar mix from Edison Coastings.
Figure. 3- Due to the scale of the project, we were all trained to drive and operate a boom lift to reach the figurative sculptures for accurate cleaning. The wet cleaning of the figurative elements of the monument occurred after repointing, and before any laser treatment.
Figure 6- My colleague Sam using the GC i-100s laser to clean the base of the Atlantic figure in the tent set-up that I designed.
Figure 8- An example of an unstable and visually obstructive crack before filling. Pink painters tape was used to mask off the surrounding area to protect it from residue staining from the custom mortar repair material.