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Faux Tortoise Shell Finish:  Faux Tortoise shell (French Ivory to some) is a finish that became very popular during the mid to late 1800's. It was common to see tortoise shell on a number of different household articles including the full and half columns of shelf clocks of the period. In the 150 or more years since these clocks were manufactured, the finish, including the tortoise shell, has usually experienced a significant amount of wear, tear and damage. Learning to repair, restore or recreate this finish can do much to improve the overall quality of your restorations.

Faux tortoise shell is a beautiful, multi-colored finish where complex shapes fade softly from one to another in random or distinctly directional patterns. Surprisingly, creating or restoring this sophisticated finish is not particularly difficult. That being said, it must be noted that the techniques for producing high quality tortoise shell with the translucence and warmth of the original is not obvious and requires a bit of faith and foresight throughout the process.

The presentation that follows is taken from the book Extreme Restoration. This technique has been used successfully in a number of clock restoration projects. They have also been posted as a “How-to” presentation on the NAWCC web site ( http://www.nawcc.org/headquarters/ktime/howto.htm ).

 

Materials: Faux tortoise shell does not require a large investment in tools or supplies but it is important to gather up the needed materials and get organized before starting a project. The following basic supplies are recommended: 

 

Glazes: Faux finishes are created using "glazes" which are nothing more than paints that have been thinned to the point of translucence.

Artist's acrylic paints work well for this type of work. Shades such as raw umber, burnt umber, raw sienna, burnt sienna, yellow ochre and black pretty well cover all the wood tones needed.

Acrylics are available from art supply stores and crafts shops such as Michael’s.

 

A product called “acrylic medium” or “polymer medium” is used along with water to thin the paints and produce the translucent glazes. One of the nice benefits of using acrylic based glazes is that they are water soluble until completely dry making clean up quick and easy.

 

Brushes: General purpose artist's brushes work well. A selection of round and flat, soft and firm should be on hand to try. A one-inch throw-away type paint brush has relatively firm bristles and works well for creating the grain effect.

 

 



Special Tools:
There are no special tools needed to create professional quality faux tortoise shell.


 

Miscellaneous: Basic shop materials such as #400 and #600 sand paper and #0000 steel wool will be needed. A primer/sealer such as alkyd enamel in a flat, off-white shade will be needed for sealing the base wood surface. Also, shellac will be needed to provide the final protective finish.


Practice Pieces:
A round wood dowel with a diameter of 1 ¼ to 1 ½ inch works well for practice, developing technique and building confidence before tackling a restoration job.

 


Reference Images:
Before beginning to create or restore a tortoise shell column, it is important to determine the appropriate design for the clock being restored. Over the years, a number of different designs were developed and used by different clock manufacturers.

Some tortoise shell columns will show a very distinct directional pattern where the shades appear to swirl left to right and upward around the column somewhat like a barber pole.

The design on other columns will show essentially no directionality and be more a collection of multi-shaded splotches that fade smoothly from one to another much like the shell of a live tortoise.

The range of colors can also vary greatly from one clock to another. Some are light to medium shades of tan while others can be very dark brown to black.

Photos of the desired pattern will be needed for a visual reference when painting the faux grain. This is actually more important than you may think. Search through photographs of clock cases and other sources until you find some clear examples of the shell pattern you wish to duplicate. Digital photos can be taken and enlarged to full size to provide a very good reference. When using photos, make sure the colors are accurate. Compare the photos to the actual pieces to confirm color accuracy.


Surface Preparation:
To produce a smooth, professional finish, it is necessary to begin with a smooth base surface.

If the columns (or dowel) being finished raw wood, a sealer such as alkyd enamel should be applied and allowed to fully cure. Once cured, it sands very easily to provide a nice work surface.

 

 

 

If restoring columns, it is likely that they were originally sealed with gesso. Gesso is a plaster-like material commonly used to seal wood surfaces and provide an extremely smooth surface for faux finishing or gilding. If the columns have gesso, it must be smoothed and (where necessary) repaired. That is outside the scope of this presentation, but is covered in detail in my book Extreme Restoration.

 



Base Color: In order to create a tortoise shell finish that has the soft, translucent look of good quality originals, a highly reflective base paint is applied to the primed and sanded columns. A bright, gloss yellow works exceptionally well for this.

 

 

 

 

 

I have used a number of different types of paint including gloss enamel from an aerosol can and acrylic enamel custom mixed to the shade desired. A base paint that is bright and reflective is the key to a finish that appears to almost glow.

 

 

 

 

Once the base coat has been applied and allowed to fully dry, inspect it carefully for runs or imperfections. Number 400 grit wet/dry sandpaper is used to very lightly sand the paint and remove any obvious brush strokes.  Don’t worry if the yellow becomes thin and slightly translucent in some areas.  This will actually add to the layered effect.


First Glaze: The colors most commonly seen in faux tortoise shell are combinations of yellow ocher, burnt umber, raw umber, raw sienna and black.

To begin the pattern an initial glaze of yellow ocher is mixed.  A common recipe is:

  - One tablespoon of acrylic medium.
  - Two tablespoons of water.
  - Add ½ to 1 teaspoon of Yellow Ocher. 

Mix the ingredients well. The finished mixture will be a thin, watery and translucent. It will thicken quickly as it is applied to the column.


The glaze can be applied in a pattern as shown or it can be brushed on evenly. It depends on the final look desired.

 

 

 

 

 

 

Notice in the photo that the translucent yellow ocher as applied here creates a rather "blotchy" look. This is pretty close to what is needed for a typical tortoise shell pattern.


 

 

 

If the pattern being copied is noticeably directional it will usually be a diagonal flow around the column. When this is the case, apply the glaze with brush strokes that create this directional pattern.

Allow this first glaze set up for about an hour before second glaze is mixed.


Second Glaze: In most tortoise shell finishes, several glazes of different colors will be applied around and over one another to build up successive layers of “scales”. The colors are selected based on study of the sample photos.  For this sample column, Raw Umber, Burnt Umber and Black will be applied to create the pattern. Burnt umber is the darker of the two browns used and will be applied first. 

The recipe for this glaze is the same as for the base glaze (one part acrylic medium to two parts water).  Add enough of paint to the mixture to produce an almost opaque finish when applied.


Study the sample photos gathered previously to get a feel for the size, shape and color of the tortoise shell you wish to create.  If the “scales” are relatively large, then a larger brush should be used. If sharp-edged, use a flat tipped brush. Alternatively, smaller or more rounded brushes are used as dictated by the pattern.

Load the brush with the glaze. The glaze is very thin, so do not take a great deal of glaze on the brush or it may run. Usually, the glaze is applied with more of a jabbing movement than a true stroke. The resulting color will be irregular in shape and density.


Continue adding "scales" of different shape and different size. Some scales may actually touch or overlap while others may have a good bit of distance between them. It depends on the overall pattern you are trying to achieve.

This first set of “scales” will set the overall shape and direction of your pattern. If the pattern you are doing is directional, then try to create scales that flow in the direction you see in your sample photos. Do not place scales too closely together since additional scales will be added using different colored glazes.

Caution #1: Don't expect things to be too attractive at this point. Remember this is only the first layer of several that will be added.

Allow this  layer of “scales” to set up for about an hour then begin the next layer.


Third Glaze: The next layer is created using the lighter brown (raw umber) acrylic.  The recipe is the same.

This layer of scales will go between as well as overlapping existing scales.  When applying this glaze it will be more difficult to see the pattern you are creating.  By applying the glaze thick in some areas and thin in others the pattern is somewhat easier to see.

Caution #2: At this point the column and paint will begin to look pretty lumpy. Don't worry. This is all part of building up layers of different colors. Things will change a lot in later steps.


Fourth Glaze: The final layer of scales will be black.  Black is used sparingly as a highlight. 

A smaller brush should be used and the highlights placed randomly, but in a flow that matches the general flow of the existing scales.  These should be softened slightly by allowing the paint to thicken for a few minutes then brush out the edges with the soft brush. At this point the column will be quite unattractive.

Set it aside to dry for at lease 24 hours so the acrylic paints fully cure and harden (important).


Smoothing: To bring out the true tortoise shell pattern it is necessary to carefully remove portions of the previously applied glazes to create thin translucent areas that transition smoothly from one shade to another. This is accomplished by carefully sanding the columns with #400 and #600 wet/dry sandpaper. 

Begin by wetting a one-inch square of the #400 sandpaper then gently sand the along the length of the column (bottom to top).  This will remove the major “lumps” and begin to lighten the overall finish. 

Work slowly and step back often to get a feel for how the effect looks. It will take very little sanding and pressure to produce noticeable results.  Over aggressive sanding will quickly cut through to the base yellow so sand gently.


Once the major lumps are removed, carefully work from the top of the column to the bottom making small circular motions.  This will remove varying amounts of glaze at different points and you will begin to see the tortoise shell emerge.  Pay particular attention to the areas where you placed black highlights as these usually require additional softening.

When sanding, consult your reference photo often. Many tortoise shell clock columns appear to transition to a very dark shade near the upper and lower ends.  This may be a result of age and wax build up or may have just been part of the production process. If you wish to duplicate this effect, simple reduce the amount of sanding as you approach the last inch or so of the column.


As the pattern begins to appear switch to number 600 sandpaper to reduce the speed of cut. This will give you more control on the overall look. This is the example columns after completing the sanding.  The pattern flows from dark to light very evenly and the overlapping layers can be seen. The bright yellow base coat is the key to creating the deep translucent look. As the browns are thinned light is reflected from the bright yellow through the browns to create the soft, warm look to the shell.

Note: As you progress with sanding it is possible that you may sand all the way through to the bright-yellow base as shown in the small spot above. Don’t worry, there is still more finishing to do.


 


Top Glaze: A final top glaze is usually added once the sanding is completed to your satisfaction. This final glaze is very important. It adds another layer of depth and softens the patterns created by the sanding.

The glaze is made with either yellow ocher or burnt umber.  If you want to bring out the lighter “yellow” tones then yellow ocher is usually better.  For a darker overall look and to “tone down” some of the lighter areas the burnt umber works well.

The recipe for the top glaze is slightly different from other glazes.  Mix:

 
- One teaspoon of acrylic medium
  - Three teaspoons of water
  - ½ to 1 teaspoon of color

The top glaze is brushed on using long strokes along the full length of the column.

Allow the top glaze to dry for an hour or more then examine it. If the overall shade is too light, another coat of glaze can be added. Once the shade is dark enough, set the column aside for dry thoroughly (24 hours) or more.

Examine the cured column for runs or roughness. #600 sand paper can be used to very gently remove any flaws or to lighten the overall finish slightly.



Final Finish: Once satisfied with the shade and pattern of the tortoise shell, it should be protected by applying several coats of shellac.

 

Shellac can be applied by brushing or using a shellac “rubber”. This will add even more depth to the finish and provide long term protection to the faux finish.

 

Once the shellac is thoroughly dry and cured, it can be polished to a high luster using a shellac rubber along with denatured alcohol and olive oil (as a lubricant). Alternatively, #0000 steel wool can be used to gently polish the shellac to a soft fine-furniture finish.


 


The top and bottom caps of tortoise shell columns are usually gilded.

The gilding must be sealed with clear to prevent oxidation and dulling.


Summary: Tortoise shell is one of the most attractive finishes ever applied to antique clocks. The great variation in shades and patterns provided almost endless variety to the basic design. As has been demonstrated, creating authentic faux tortoise shell columns is not overly complex and is actually quite forgiving as long as a clear idea of the desired final finish is understood. Learning to create or repair this antique finish will help to improve the quality of your case refinishing and clock restorations. Find an old worn column or even a wooden dowel and give it a try. You will be surprised at how talented you are.

 Faux finishes were far more common on mass produced American clocks from the 1800’s than most people realize. In addition to tortoise shell, faux wood grain was frequently used on the sides of clock cases as a cost effective alternative to expensive imported veneers. Gilding or gold-leaf represents yet another decorative finish used extensively on clocks of this period. These as well as other finishing and restoration techniques are the central focus of the e-book Extreme Restoration.