168 North Michigan Avenue
Location
Chicago, ILRestoration Architect
BTL ArchitectsInstallation Contractor
Central Building & Preservation L.P.General Contractor
W.E. O'Neil ConstructionApplication
Terra Cotta MasonryForming Method
RAM Press, Hand Press, Slip Cast, ExtrusionMarket
CommercialRegion
Midwest168 North Michigan is the historic restoration of Marshall and Fox’s 1916 Atlantic Bank Building in Chicago, Illinois. Boston Valley Terra Cotta worked with restoration specialists, BTL Architects, and Central Building & Preservation to recreate terra cotta masonry for the building’s signature façade.
Named after the patron saint of hospitality, the Hotel Julian is a luxury hotel in the heart of downtown Chicago, located diagonally across from Millennium Park. The redevelopment of this building was led by Oxford Capital Group and Quandrum global. The Hotel Julian stands at 17-stories tall with a five-story addition wrapped in a glass curtainwall, designed by Hirsch Architects.
Categorized as: Commercial, Extrusion, Hand Press, Midwest, RAM Press, Restoration, Slip Cast, Terra Cotta Masonry,
THE RESTORATION PROCESS
The restoration process begins with the Pre-Design phase to determine the scope of the project and the needs of the restoration. A site survey is conducted, tagging and documenting pieces that need to be replaced. Digital scanning and photogrammetry are used to create 3D models of the blocks marked for reproduction. Samples of the original masonry units are brought back to Boston Valley to be used as reference.
FINISHING TOUCHES
After fabrication, masonry units are brought into the finishing department, where Boston Valley sculptors apply final details before glaze application and firing. The white glaze was developed in Boston Valley’s glaze lab to match 168 North Michigan’s original surface treatment.
After terra cotta units are glazed and fired, they are then tested for continuity and alignment. Dry fit mockups are a useful part of Boston Valley’s quality control process to ensure the accuracy and precision of approved drawings. After the mockup is approved, the units are then carefully labeled, packed, and shipped to the job site for installation.
In the process of recreating the masonry for 168 North Michigan, all four forming methods were used in production:
Slip Casting: Liquid clay is poured into a plaster mold and allowed to dry until the desired wall thickness is reached. The excess liquid is evacuated, the clay dried, and the mold is removed, resulting in a fully formed masonry unit. Slip casting is used for ornamental terra cotta pieces and units that require a hollow interior for anchoring purposes.
Hand Press: Molds are filled with clay by hand, then rubber mallets press clay against all five faces of the mold to a set thickness. Hand Press is used for sculptural pieces that contain non-linear detailing or details with undercuts.
RAM Press: Using a two-piece mold and a hydraulic press, a clay slug is placed on the die and then pressed into its form. The RAM press is used for less sculptural terra cotta pieces or simple units without an undercut.
Extrusion: Clay is pushed through a large extruder and metal die to create a linear profile with a hollow cross section, then cut to the desired length. The extrusion method is used to efficiently create many duplicates of the same profile piece.
THE RESTORATION PROCESS
The restoration process begins with the Pre-Design phase to determine the scope of the project and the needs of the restoration. A site survey is conducted, tagging and documenting pieces that need to be replaced. Digital scanning and photogrammetry are used to create 3D models of the blocks marked for reproduction. Samples of the original masonry units are brought back to Boston Valley to be used as reference.
In the process of recreating the masonry for 168 North Michigan, all four forming methods were used in production:
Slip Casting: Liquid clay is poured into a plaster mold and allowed to dry until the desired wall thickness is reached. The excess liquid is evacuated, the clay dried, and the mold is removed, resulting in a fully formed masonry unit. Slip casting is used for ornamental terra cotta pieces and units that require a hollow interior for anchoring purposes.
Hand Press: Molds are filled with clay by hand, then rubber mallets press clay against all five faces of the mold to a set thickness. Hand Press is used for sculptural pieces that contain non-linear detailing or details with undercuts.
RAM Press: Using a two-piece mold and a hydraulic press, a clay slug is placed on the die and then pressed into its form. The RAM press is used for less sculptural terra cotta pieces or simple units without an undercut.
Extrusion: Clay is pushed through a large extruder and metal die to create a linear profile with a hollow cross section, then cut to the desired length. The extrusion method is used to efficiently create many duplicates of the same profile piece.
FINISHING TOUCHES
After fabrication, masonry units are brought into the finishing department, where Boston Valley sculptors apply final details before glaze application and firing. The white glaze was developed in Boston Valley’s glaze lab to match 168 North Michigan’s original surface treatment.
After terra cotta units are glazed and fired, they are then tested for continuity and alignment. Dry fit mockups are a useful part of Boston Valley’s quality control process to ensure the accuracy and precision of approved drawings. After the mockup is approved, the units are then carefully labeled, packed, and shipped to the job site for installation.
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