Ceiling medallions may need repair or replacement, such as this elliptical medallion from Rockland, Fairmont Park, Philadelphia. An impression was taken of the existing plaster, then new plaster elements were cast. Photo: David Flaharty.

Ceiling Medallion. Ceiling medallions are often in greater jeopardy than cornices because the joist-lath-base-coat support system is susceptible to deflection and the force of gravity. The problems of ceiling failure are more frequent in the centers of parlors because circular-run and shop-cast ornament is often quite heavy and was not historically attached with any additional mechanical fasteners such as bolts and screws.

If the lath or keys have failed, plaster ceiling ornament may be saved, in whole or in part, by removing floor boards above, then drilling and injecting each lath with an elastic acrylic or epoxy material to reattach plaster to lath, and lath to the joists. This is a recently developed procedure which should only be undertaken by experienced professionals. The consolidation and reattachment process has been used successfully in period structures with dramatic results when important plaster and painted surfaces would otherwise have been lost.

Historic lighting fixtures often hung from elaborate ceiling medallions. When these fixtures were later converted to gas and electrical service, the central ornamental plaster canopies were sometimes damaged by insensitive tradesmen. More recent adaptive use projects may have caused additional damage.

Damaged ceiling medallions can be repaired by carefully removing representative plaster ornamentation, molding and recasting in the shop and replacing the new enrichments so that they align perfectly with the original pattern. Polyvinyl acetate bonding agents are applied to the background and ornament so that the adhesive plaster grips tightly. Alternatively, a severely damaged medallion can be replaced using the fragments as physical documentation to cast a visually accurate replacement.

Sections of plain-run circular molding may also be repaired by determining a section through the run and the radius from molding to pivot point. As with cornices, the run should be made on a bench to a length greater than required, then cut and fit in place. Circular run sections are installed using plaster adhesives on bonded surfaces or modern construction adhesives after referring to manufacturers' instructions as to whether the adhesive is recommended for use on wet or dry materials. Coarse-threaded, galvanized screws are often countersunk to aid the bond; if possible, the screws should be inserted at points that will ultimately be covered with cast enrichments.

Ceiling medallions frequently appear in matching double parlors. It is not unusual for one ceiling to fail while its mate remains undamaged. The flat plastered ceiling over the location of the missing medallion often has a "ghost," confirming that a ceiling medallion once ornamented the parlor. The missing medallion may be remanufactured by securing a section, dimensions, and samples of cast enrichments from the surviving ornament and accurately following the original procedure. The ceiling on which the new work is to be set should be examined for its soundness and, if necessary, relathed (with self-furring metal lath) and plastered. The pivot point for a circular run is screwed into a wooden block, force-fit into the center electrical box, and removed after the run is completed.