medallions - steps for making decorated ceiling ornaments

In the days of high ceilings, fancy cornices, and hanging chandeliers, an elaborate center medallion was the finishing touch to any ceiling. Most high-style homes - especially row houses - built between the early 18th century and the Great Depression had these plaster ornaments. Their design schemes followed the house's overall styling, perhaps Greek Revival, Second Empire, Italianate, or Colonial Revival.

Few have survived intact. If the medallion is not repairable, you can create a new one that matches representative elements of an original or the overall detailing of the house - say, lines from the cornice and ornament in the mantel. A job for a skilled plasterer, it involves turning a round base and then adding cast enrichments. Here's how I produce plaster medallions. If you're experienced, use the directions to tackle the project yourself, otherwise use them as specifications for a professional.

If you've got a large medallion, chances are you've also got a high ceiling. Plastering 11' up, 14', or more, is not step-ladder work; you need solid footing and a good deal of workspace. I recommend 8' x 8' staging. Attach flood lights so you can see and a mortarboard to hold ornaments.

Before getting started with the plaster, run rough electrical service to the center of the room. Install a 4" junction box there, mounted flush with the ceiling. Snap a chalk line from the center of a chimney breast of main wall and through the middle of the electrical box. This line will serve as a reference point for the segmented enrichments. Also mark the locations of joists and other good nailers for fastening the suround. Make sure the ceiling is sound. If not, repair or replace damaged lath and plaster, or install drywall. If you open up the ceiling for electrical work or repairs, take the opportunity to add additional blocking for anchoring screws.

There are two parts to most medallions: a run surround and cast enrichments. We'll get to turning a run surround, but first, you'll need to make a casting mold. Prepare a model (a piece from an original medallion or new sculpture in clay or wood), then glue it to a flat marble surface and fence it with wood or sheet metal. Seal around the fence with clay or plaster to prevent leakage.

Lather the model with an alcohol-free neutral liquid soap; the soap film acts as a separator so that the rubber molding compound does not stick to the prototype. Allow the soap to dry and then burnish it (wipe away any soap powder) with a dry brush.

Originally, medallions were cast in melted hide-glue molds, but now there are many modern mold-making rubbers available. Silicone is good, but it's needlessly expensive. Polysulfiedes are OK, but they have no memory (they loose their shape unless you keep a plaster cast in them at all times). Latex rubber is good because it resists tearing, but it must be painted on in as many as 20 coats and it shrinks when it hardens. That can mean your enrichments, don't line up well. The best option is a two-part mixture of liquid urethane rubber in 30-durometer hardness. It is inexpensive, has a long life, and holds its form.

For standard ornaments, cover the entire model with rubber by 1/8" to 1/4". More than that, and the mold will be stiff and it will be hard to demold the plaster pieces later. However, for large enrichments, or those with very deep relief, extra rubber may be needed so it will keep its shape.

Casting Enrichments

Specify casting plaster for the ornaments. It contains starch, which creates a hard, damage-resistant surface. Moisten the urethane mold with water from a plant sprayer before pouring in the plaster. No separator is required. Pour the plaster into the mold slowly and evenly. To ensure that it settles into the nooks and crannies, push it in place with a brush and gently jiggle and slap the mold.

Just before the plaster sets, scratch the back surface to make a better bond between ornament, adhesive, and the ceiling. I key the casts with a notched trowel, but any tool that creates grooves for the adhesive to grab will work.

Plaster sets in about 15 minutes, but follow the manufacturer's directions. Carefully peel the mold away and set the enrichment aside. You can repeat this process for as many pieces as you need. You might even cast a couple extra, just in case. Also, cull any defective pieces.

Design Details

If possible, use the house's existing medallion, or representative remnants, as a model. If not, try examples in neighboring houses. Also, ornamental plastering shops have large collections of medallion parts taken from other old houses. Pick and choose the surround profile and enrichments so they match the overall patterns of the house's cornices, mantels, and mouldings. To reproduce ornament that's only documented in pictures or just a memory, you can sculpt the elements in clay. Refer to stylebooks and trade catalogs of the house's period for more clues.

To record the profile of a surround moulding, you can scribe it, use a profile gauge, or best, make a cross section. To do this, cut a thin saw kerf through the moulding. Then slip a piece of 22-gauge galvanized metal into the kerf and trace the moulding. Now you have a perfect replica of the design. To copy existing cast pieces, use the objects themselves as models for the molds. If they are part of an existing medallion that's on the ceiling, use a paste rubber and mold them in place. To copy an existing run surround, slide a piece of sheet metal into a thin crosscut kerf.

You'll have to determine whether the medallion will have a run surround moulding (a turned plaster base). Many medallions have one of these, with cast enrichments applied to it. However, after 1850, especially in the South, medallions might not have had a run surround.

Traditionally, run surround mouldings were turned directly on the ceilings. However, for medallions that are less than 36" in diameter, I recommend running them on a bench and then applying them to the ceiling. The process is essentially the same; it's just harder overhead and upsidedown. For benchwork, use a mortarboard that has a plastic laminate top. It's non-absorbent, making removal and cleanup easier. Mark the circumference of the medallion by placing a pencil against the arm and spinning it.

Whether turning in place or on the bench, you'll need to build a jig consisting of a template and a spindle to turn it. To create the template, transfer the surround profile to 22-gauge galvanized sheet metal stock and cut it to rough shape with tin snips. Then carefully file it to the exact profile. I use half-round, rat-tail, and flat files, as well as a carbide rotary file chucked into a drill press. For benchwork, the template should be designed so the base has a 4" diameter circle in the middle - this is where the electrical box will go.

The blade will ride on a wood arm (or stock). Anchor the arm to a nail in the tabletop, or to a screw turned in a wood block that's force-fit in the ceiling's electrical box. Set up the arm with a hole for the spindle. I use a shop-made sheet metal bracket with a notch cut in it. Attach a slipper (an additional wood member that forms the top of a T). A brace (a wide plank or plywood support that lays over the T to prevent flexing or vibrating of the arm as it spins) is especially recommended for running the disk on the ceiling because it catches excess plaster. Nibs (protective sheet metal strips) will keep the edge of the slipper from wearing down too quickly.

For bench turning, apply a separator (a barrier to adhesion) to the work surface. Petroleum jelly, electricians' lubricants, soap, and oil will work, but if the surface is too slippery, the plaster may move. And if that happens, you'll have to scrap the run moulding and start over. I use a separator that I make myself. It's a combination of kerosene and stearene (available from hobby shops that sell candle-making supplies). Heat the kerosene in a double boiler and melt the granulated stearene into it. Let it cool, and point it on the worktable.

If you're spinning a surround in place, first scarify (scratch) the ceiling so it'll have a mechanical bond. Then paint it with polyvinyl acetate (a bonding agent sold under various names, such as Plasterweld). It blocks moisture absorption and improves adhesion. For added security, drive galvanized bungle-head screws into the ceiling and leave the heads exposed where the plaster will go. Trowel equal parts lime putty and plaster and add a powdered retarder to slow the setting process. This produces thick enough plaster to stay put, while allowing you time to work before it sets. (Wear rubber gloves when working with lime.)

Medallion Makeup

Ceiling medallions look complicated, but on closer inspection, you'll notice that they are actually many small, repeating designs. From the center outward, medallions typically consist of a canopy (not shown here) made of metal or cast gypsum, a ring of small leaves, a center cluster of ornaments, a plain-run or enriched surround (either round or elliptical), and a perimeter enrichment of leaves or anthemia (not shown).

The ceiling will determine what kind of adhesive to use. If it's lath and plaster, a simple gypsum plaster is the best glue. (make sure three-coat plaster is strong and lath is firm or the added weight of a medallion could be disastrous.) In the case of drywall ceilings, the paper surface inhibits plaster adhesion. So use white glue mixed with just enough plaster to thicken it so it fills voids. The mixture should be the consistency of sour cream; I have never measured, but it's probably 10 to 20 percent plaster, the rest glue.

Construction adhesive is another good option for drywall ceilings, but it takes longer to set. It therefore requires fastening the medallion with screws - not a bad precaution with any adhesive, especially on drywall ceilings.

Predrill holes in the disk and countersink them to receive galvanized, buglehead deck screws. Unlike predrilling for screws in wood members, these holes should be sized larger than the screw shanks so the threads will pass without grabbing. Otherwise, the screw may crack the plaster. Drill pilot holes at slight angles (say, 5 to 10 degrees) so the mold will not loosen if the screw releases slightly. Where there is no solid nailing behind the drywall, toggle bolts are an option.

For an existing ceiling, remove paint so that plaster meets plaster or clean drywall. Scarify plaster ceilings. Paint adhesive on the back of the disk, and press the ornament in place, aligning it with he chalk marks and over the electrical box. Then remove it. Inspect the adhesive for complete coverage and let it set briefly so the piece sticks quickly when reapplied. Finally, put the medallion in place and drive screws into the predrilled locations. A variable speed drill is a necessity. Fill uncovered screw heads with a thinned plaster mix before finishing

Historically, enrichments were soaked in water before mounting to prevent the plaster from drawing the water out of the adhesive. However, modern bonding agents block moisture migration so the enrichments need not be saturated. Paint polyvinyl acetate on and allow to dry. It strengthens the bond, decreases the weight of the enrichment by one-third, and allows the painter to begin work sooner.

The trick to installing enrichments is placing them correctly. To ensure that they are spaced equally around the 360-degree surround, I make a protractor from a piece of Masonite or cardboard. Cut a circle of the needed size and paint it white. Place a hole in the exact center and, using plane geometry, draw radiating lines for the center of each enrichment. When it's time to apply the enrichments, transfer the marks to the surround. Make sure the first line rides the chalk line from the chimney breast or wall. To space enrichments equally from the midpoint, cut another layout disk (this one must be an accurate circle) to the radius the enrichments are to be distanced from the midpoint. Either trace it or fasten it temporarily and place the enrichments against it.

Plaster is the best glue for attaching enrichments to the run surround. For enrichments outside the perimeter, use whatever is appropriate for the ceiling surface. Score both the ornament and the surface location. I slather a piece, stick it up and remove it and set it aside. Then I move to the next piece, and so on. Once four or five pieces are glued and have thickened slightly, I return and attach them in order.

The medallion can be polychromed, gilded, or painted. With a reproduction medallion in place, your parlor, dining room, or living room will once again have its original glory.

Plaster Master Supply
4308 Shankweiler Rd. Orefield, PA 18069
Phone (610) 391-9277 · Fax (610) 391-0340

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Construction & Renovation

Award-Winning Steps for Making Decorated Ceiling Ornaments