Here, a damaged floral motif was cut back to well-adhered, existing plaster with an oscillating multi-tool (photo, left). The damaged decorative finish coat was then scraped down to the existing base coat. The replacement piece was lined up to its desired location, scribed to the cut-back opening, then trimmed and dry-fit in place (photo, right).
With the replacement piece sized and properly aligned, the base coat was removed down to the wooden lath. The edge of the remaining plaster was held in place while the base coat was carefully cut away (photo, left). The existing plaster was scored with a putty knife; the knife slowly cut through base coat (photo, right).
The existing ceiling was on the thin side (about 1/4 inch thick), which was unexpected given the robust nature of the mansion’s overall construction. The thin ceiling added to the degree of difficulty removing damaged portions of the ceiling and installing new replacement pieces.
A bonding agent was used to adhere the new plaster pieces to the old, dusty lath. Before the bonding agent was applied, the existing wood lath was wetted down using a pump sprayer (photo, left). Plaster Bonder by USG was applied to exposed lath (photo, right) and to the back of the replacement piece. The bonder takes about an hour to become dry and tacky.
The bonder was applied to the back of the replacement piece (photo, left). To adhere the new decorative piece to the ceiling, a thin layer of plaster (mixed with a lot of gauging and just a small amount of lime in order for it to set quickly) was applied over the bonding agent (photo, right).
Setting the new pieces, they had to work fairly fast and know precisely where the new piece was located. Also, they had to apply the right amount of plaster fill to flush up the new piece with the existing ceiling (photo, left). While the replacement piece was being held in place, the excess plaster squeeze-out was pushed into any voids and the edges tooled (photo, right).
Because the existing ceiling was painted and lime putty cannot adhere to paint, the new touch-up work had to be feathered right up to the edge of the painted surface. While texturing to match the existing ceiling, they wiped excess plaster off the paint (photo, left). A rodding spatula was used to help texture the ceiling and scrape back the new plaster (photo, right). After the lime putty dried, parging (spackle) was applied over the hairline seam between the new plaster and the existing painted surface and sanded smooth to cover the seam.
