Ravenna, Italy Double-Reverse process to make or restore mosaics

Step by Step with Materials and Tools: Betsy Gallery www.elizabethgallery.com

1.Preparing the Design

On a temporary board a little larger than your design (can be wood or heavy cardboard) tape down the design, in color, in the exact size you will make the mosaic.

Clear contact paper or Mosaic Mount* (better tack but more expensive)--a little larger than your design. Pin or tape contact paper sticky side up over the design.  You will place the tesserae on this temporarily. Do not cut smalti over this contact paper as it will lose its tackiness as it fills with glass shards and dust.

2 .   Cut tesserae with nippers or hammer and hardie and place close together on sticky contact paper over the design, with about 1/16,” or a little less, space between the pieces.

Begin with the main image. First make the eye, if it has one. Then outline the image, making sure the line is smooth and follows the design. Then create the principle interior lines. Then fill in the remaining spaces. It is important to start with an outline to create the shape.

If there is a border, next complete the border. Then fill in the background.

At this point you can make any changes you want.

3.  Affixing Cheesecloth

Make rabbit skin glue. (You can soak it overnight, as in the instructions.) For a 13x13” mosaic you will need about 3 tablespoons of rabbit skin glue granules in 2.5 cups of water. Heat the glue to the simmering point but do not boil. Simmer about 20 minutes. Boiling destroys the properties of this glue. Rabbit skin glue is the best for this purpose. Substitutes do not work well.  I use a pot that I bought at a thrift shop, which I have exclusively for glue.

Cut two layers of cheesecloth about two inches larger than the mosaic.  Rinse the sizing out with hot water. This will shrink it. Lay out flat or hang to dry a bit—as open as possible to avoid drying with rolled edges.

Put one layer of cheesecloth on the face (the part you will see when it is finished) of the mosaic. If it is a bit damp it will settle down easier.  Using the stippling brush, dip the brush into the hot glue and start in the center of the mosaic and tamp the cheese cloth down onto the tesserae. Make sure that the tesserae which are low come in contact with the cheesecloth and glue.  When the first layer is glued, place the second cheesecloth on top and repeat. Make sure that

the low tesserae are in good contact with the glue and cheesecloth.  This will save a lot of headaches later on.  Extend the glue a little over the edge of the border of the mosaic. It will make it a lot easier to cut the cheesecloth close to the mosaic once the glue is dry.

4. Dry Thoroughly: Make Repairs

 Let dry thoroughly. If it is sunny, put it out in the sun. If the temperature is about 68 degrees or more the glue will probably dry overnight.  Make sure the glue is very dry before continuing.  If you can leave it two days, even better. In the winter if it is damp it may take longer. You can use a hair dryer to make it dry faster too.  And/or put it in front of a fan overnight.

5. Place a board on top of the face of the mosaic. Turn the mosaic over so that the back with the contact or Mosaic Mount paper is facing up. Remove the contact/Mosaic Mount paper slowly, holding it parallel to the surface. Do not jerk it up.  At this point you will see if all the tesserae are firmly attached to the cheesecloth underneath.

If any tesserae are loose, glue them down to the cheesecloth with a drop of Weldbond. Put waxed paper under the area with Weldbond to keep it from attaching the mosaic to whatever it is resting on. And let dry thoroughly. Use hair dryer if you are in a hurry.

You can use a small paint brush to brush over the backs of the tesserae to see if any of the pieces are loose. Listen for a click that tells you that a piece is knocking against its neighbor.  It is very important that the tesserae are very tightly attached to the cheesecloth. Any loose tesserae will be lifted by the thinset and make a mess. If one comes up in the thinset, set it aside, clean it off and it will be used later on to fill in the space.

6. After any repairs are dry, use an exacto blade to cut the excess cheesecloth away from the border, cutting right next to the border tesserae. You will find it much easier to cut the cheesecloth here if the edge has a bit of the glue, making it stiff.

Spread some very fine colored sand into the interstices between the tesserae, about ¼ of the way up. Use a watercolor paintbrush to spread it around. At this point you may find more loose tesserae, which you can reattach and wait to dry (again).

 7. Backer Board. (Many, many possibilities for this substrate. Choose one that is appropriate for the use for which you will make the mosaic.  No wood outdoors or in humid places (e.g. the bathroom).  I do not use wood at all for anything applied with thinset.

 Cut the backer board the exact size of the mosaic. Mark which side is the inside and which end is up. There are generally slight variations in shapes and you want the mosaic sitting in the correct orientation.

If you need to prepare a hanging device in advance, now is the time to do it.

8.  Thinset

There are many kinds of thinset. Some dry very fast (two hours) and others take over night to dry enough to remove the cheesecloth.  The fast drying thinset has only a 20 minute “open time” during which it can be used after mixing with water. But you can then remove the cheesecloth in two hours.

In the beginning you may want to use the normal thinset with a longer “open time” which allows you more time to work with it. Buy a good quality thinset which has an additive to make it stronger. Read bag instructions for mixing.

Mix the thinset thoroughly. Follow directions on the bag. The normal thinset usually requires a 5 or 10 minute slaking time after the initial mixing and before remixing and using.  For a 13x13” mosaic you will need about 2.5 cups of thinset and about ¾ cup of water, or add more water if it is too stiff, or if too loose, add more thinset.  Mix well, making sure there are no lumps or dry spots. Should be about the consistency of peanut butter or a little looser.

Using the flat side of a notched trowel carefully spread the thinset over the back of the mosaic, covering all the tesserae, pushing down slightly to get it between them, but scraping off most of it from the backs. (The sand will keep the thinset from emerging all the way through the spaces between the tesserae.)

Using the flat side of a notched trowel, spread about ¼” thick thinset on the correct side of the backer board (remember which side is the top…as you will be covering up your previous marks). Once the thinset is spread evenly, use the notched side to make furrows in the thinset. The notches on the trowel are to be the same depth as the tesserae are high.

Place the backer board with the thinset onto the back of the mosaic. Flip the mosaic so that the cheesecloth is up. At this point if the mosaic is a bit off-center of the backerboard, you can slide it into position.

Once the mosaic is in the right position, place the board on top of it and tamp it down using a mallet. Start from the center and move toward the outside. This will insure that all of the

 tesserae are imbedded into the thinset. Remove that extra board and manually press the border down making sure it is in good contact with the backer board.

At this point I put the whole thing up on a lazy Susan, and using a pallet knife I seal the edges of the board with the mosaic so the edge looks like one piece.

Let dry thoroughly. Clean up equipment soon with a lot of water, but do not put wet thinset in any quantity into a sink or toilet or any drain as it will harden and clog. I have a place in my garden where I dump cement from cleanups.

9. When the thinset is very dry, spray the cheesecloth heavily with warm water and let it sit about 15 minutes to soften the glue. Spray again and pick at the edges of the cheesecloth to see if it is loose enough to remove easily. If not, spray enough water to remove the cheesecloth easily. At this point water will not hurt the mosaic. Pull the cheesecloth slowly parallel to the surface.

Once the cheesecloth is removed, pour hot water over the face and scrub with a plastic dish brush to remove residual glue. Weldbond will appear an opaque white.  Then go over it with a dental tool removing any thinset that it where you do not want it, and removing the white caps of Weldbond, which will be soft by then.

 If there are any tesserae that came out when spreading the thinset, you can make a little hole in the dried thinset and replace the piece with a bit of new thinset.

Materials List

Permanent backer board: Wedi board; Schluter Kerdi board; Hardibacker etc. If you use Schluter, you will need to attach it to plywood afterwards, as it is flexible even with the thinset on it.

Hanging hardware and wire

Exacto knife and blades


Particle mask

 Thin Rubber gloves

Cheesecloth:  fine weave

 rabbit skin glue

 stippling brush

tile/smalti etc.

colored sand—I use black to deepen the interstices between tesserae

Waxed paper


Spray bottle

Watercolor type paint brush: to move the sand around

Heavy cardboard square or board bigger than mosaic design: to set up the temporary base. If wood, it can be used to tamp down after thinsetting.


Mixing bowl

Wheel nipper (Montolit are best.) or hammer and hardie


Notched trowel with right size notches for tesserae

Needle nose pliers

Wirer cutter

Dental tool

Plastic scrub brush

Pot for glue

Wooden spoon to stir glue

Hot plate or stove

Flat board and mallet

Pallet knife

Table spoon measure and 1 or 2 cup measure

Rubber mallet


Mosaic Mount is available from Ventura Tape. In Santa Barbara you can order it at the Santa Barbara Stained Glass shop at 4129 State St.  683-2628.