1. Producing the mold for reproduction of old crown moldings
On the picture you can see a crown molding in a house that was originally built in 1905. Throughout the years there have been many layers of paint applied.
As you can see part of the molding was severely damaged due to the water leak from the bathroom directly above it. Below we will describe what exactly needs to be done in order to restore damaged parts of the molding to its original condition. Use respirator mask, safety glasses and follow general safety rules throughout entire process.
First, you need to cut out the damaged piece of the molding to create a space to install the new molding. For cutting out you need to make two vertical cuts using an oscillating tool at both ends of the damaged area so the undamaged parts of the molding stay intact. After completing the cuts you can remove damaged piece by chisel and hammer thus creating a clean opening for installation of newly created pieces of molding. Use the drill to find beams on the wall and the ceiling within the opening. Mark the beams with pencil lines so you could see those lines when installing new moldings.
Next, in the same room, select an area of undamaged molding 2 to 3 feet long to use it for creation of the replication mold. Try to select an area where the top and bottom flat parts of the molding remain in best conditions. The pieces to use should have strait lines, not affected by house settling.
After making a selection you must prepare the selected piece for the application of silicone rubber. Fill any dents in the area with new plaster mix. Depending on the depth of the dents you may need to apply several coats of plaster to fill the dents perfectly.
After the dents are filled in and plaster is dry use sandpaper to make the molding surface smooth and remove any imperfection from old layers of paint covering original design.
Once the selected piece is prepared you can use a brush to begin application of silicon rubber. This step will require 3 to 4 coats. The average time to dry for each layer is 2 hours depending on the thickness and kind of silicone rubber. You can check if it is ready by gently tapping your finger on it to see if it is sticky. If it is not sticky your piece is ready for the next coat. After you have applied the last coat let it dry for a minimum of 8 hours or even better to let it sit overnight.
Once the rubber is dry you can begin to make a plaster shell. Apply plaster on the surface of silicon rubber using spackle knifes. Apply it until the shell is about ½ inch thick. Allow the plaster to get hard and dry, if possible use a fan for several hours.
After the plaster shell is ready you need to remove it from the molding surface in one peace. In order to do that you need to attach a metal structure to the shell. But first you need to assemble the structure. It should be created the way that after you remove the structure (with the plaster shell attached to it) and put it on the table the shell should be in a horizontal position.
Remove the plaster shell and its structure and put it on the table. Remove the silicon rubber that you applied on the original molding and put it inside of the plaster shell. You may need to adjust the rubber film a little bit so the rubber inner surface follows the shell surface perfectly.
2. Molding and installing new pieces
After you have prepared the mold you are ready to mold new pieces of the molding. You will need molding plaster, water and burlap fabric to put it in the molding in order to make it strong and brake resistant.
Put some molding plaster in the bucket (amount of plaster needed will vary depending on the molding length, width and depth) and add water. Mix it up with a drill and a mixer following the mixing instructions. Mix it well so the entire mix has the same consistency. Pour the mix in the mold and let it sit for a minute. After that put your hand in the mold (use rubber gloves while doing it) and gently follow the lines on the bottom of the mold in order to push out the ear bubbles remaining in the plaster mix. Do it for a minute or two. Once you are done with that, submerge the piece of burlap fabric (which should be cut matching the size of the mold) in the mix in the mold. Few minutes later the mix will start to get thicker. Let the molded piece to get hard enough (usually it takes 8-10 minutes) to remove it from the mold.
Remove the first piece of the molding from the mold and repeat the step described above to produce the next pieces. Mold as many pieces as you need to fill the opening.
Newly molded pieces are ready to be installed. For installation you will need the plaster mix again but little thicker that the one used for molding process. Apply the plaster mix on the back of the molded piece and insert the piece in the opening right next to the original molding. Hold the new piece tight simultaneously against the wall and the ceiling until you feel that the plaster is hardened and the piece can stick to the wall and the ceiling without your support. Usually it takes 2-3 minutes. Make sure you hold the new piece the way that the lines of the new molding continue the lines of the original one. For that purpose you may use thin rope, floss or a laser beam to connect the lines of original moldings through the opening. New pieces should follow the lines created by floss or the laser.
After you filled the opening with the new pieces of molding you should screw the pieces to the beams behind the wall and the ceiling. First, predrill the holes through the moldings and beams using the lines prepared by you to mark the beams. Then, in those holes put the screws long enough to penetrate the beam at least for 1/2 of inch. Repeat this step for every beam on the wall and the ceiling.
After putting the screws you need to fill the holes formed throughout the restoration area. For filling use the plaster mix with the same thickness that you used for installation of moldings.
After this, leave the moldings until they get completely dry. Usually it takes 2-4 days depending on the season of the year.
З. Preparation for painting and painting of newly installed pieces.
After new moldings get dry you need to prepare them for painting. Uneven parts of the moldings teed to be sanded. Use 60- to 80-grit sand paper for rough sanding, mostly to sand areas with hardened plaster mix. Once done, remove the dust with the brush as much as possible. Apply colored plaster mix as shown on the picture (by using different colors of pigment for coloring plaster you can easily find spots that you plastered last time) to the dents or spots that still need to be filled. Let the plastered spots dry and then sand them with 100- to 120-grit sandpaper. Brush it again to remove remaining dust. Repeat these steps of sanding, brushing and filling as much as needed to fill the dents perfectly. For the last time sanding use 150-180 grit sandpaper.
After sanding is done moldings need to be primed. Use water-based primer. It is recommended to make the primer thinner by adding little water so it can penetrate surface of the molding. Apply primer with a brush that is approximately half of the width of the molding.
After the primer is dry (about in 1 hour) apply at least two coats paint. Depending on the paint color it may need a third coat of paint for complete coverage of the primer.
4. Application of gold leaf After paint is dry you are ready to apply a gold leaf to the moldings. Before starting actual gold leaf application you need to figure out which parts of the molding you want to be highlighted by gold leaf. Usually, gold leaf is applied to the parts that are sticking out. Different people may decide to highlight different parts of the molding depending on their taste.
Once you make that decision, use an artist’s brush to apply special adhesive material “Gold Size” to the spots that you want to be highlighted by gold leaf. Follow Gold Size applycation instructions. Apply it moderately, creating very thin layer of adhesive so it does not drip. Once you complete the entire surface leave the glue to dry for several hours (exact time to dry should be indicated on the packaging of adhesive). When time comes adhesive will be slightly sticky, not completely dry. That’s when you should apply the gold leaf. Otherwise, if you let adhesive dry longer it will lose the stickiness and will not be able to hold the gold leaf.
It is better to cut gold leaf into stripes so you can use the material with minimal loss. After you prepared the gold leaf apply it gently by hand against adhesive on the molding. Gold leaf should stay on the molding surface. Cover entire surface of adhesive with similar manner.
After you are done with application of gold leaf use dry brush to clean the molding from any dust and extra, unneeded parts of gold leaf that my remain on the adhesive. This will give the molding nice and finished look.