Sunday, August 28, 2011

Restoring Boulle

One of the most rewarding and frustrating projects I have done over the years is restoring Boulle furniture. By common usage, the term "Boulle" refers to the furniture which is made with brass and tortoise shell marquetry, generally from the last quarter of the 19th century, in Paris.

This period, referred to as Napoleon III, represented a revival of the technique of marquetry popular during the period of Louis XIV, when Andre-Charles Boulle was the most important ebeniste in France. Of course, the early work by Boulle and his contemporaries was made with a much higher degree of quality and workmanship. In fact, the type of tortoise shell used during that time was from a different sea turtle, which was a meat eater, and produced a much thicker shell. The thicker shell was perfect to match with the thicker sawn veneers available at that time.

The shell used during the Napoleon III period was from a sea turtle which was a vegetarian, and the shell was much thinner, also a good match for veneers used later in the 19th century, produced by slicing machines.

The term "tortoise" shell is confusing, since a tortoise lives on land and a turtle lives in the ocean, but that is the term which has always been used for this method. C'est la vie.

After determining which species of shell is used, it is necessary to select the appropriate shell for restoration from a turtle of the same age. Turtles live a long life, and the young turtles have very dark pigment in the shell which forms large areas of color, contrasting with the naturally clear background. As the turtle ages, these blobs of color spread out and become rays of dark, turning into spots of color in very old turtles.

Of course, sea turtles have been on the endangered species list since 1986 and are a controlled substance, so only the restorers who have old stock (and can prove it) have access to this material. I personally have about a kilo of shell, of both species, which I purchased legally prior to the ban, and I use it for appropriate restoration projects.

Another source of shell is damaged furniture, but in that case only very small pieces can be salvaged. There is a plastic shell substitute, used in the guitar industry that works, and there is a substitute shell made using protein glues and coloring, a recipe that first appeared in the 18th century and, more recently, was perfected by Don Williams, working at the Smithsonian.

The other material, brass, is common, but must be annealed so that it is soft. It is hard to do that in a small shop, since it is best done in a large oven, where the sheet is evenly heated and allowed to cool naturally.

Almost all Boulle furniture is damaged by workers who do not understand what to do, and usually resort to nails or epoxy or plastic filler to repair the surface. These efforts make the proper restoration difficult. It is essential to understand that the traditional adhesive, fish glue, is the only adhesive that should be used to restore Boulle. Attaching brass to wood is difficult, since under environmental changes, the wood and brass move in opposite directions. This constant tension between the marquetry and the substrate is controlled by the properties of fish glue, which allows a small amount of sheer movement during these fluctuations, while keeping the surface stuck in place. Fish glue is used for tortoise shell, brass, pewter, mother-of-pearl, ivory, bone, horn and other exotic materials which do not move in the same manner as wood veneer.

The other problem with brass is corrosion, which attacks the brass when the finish fails. I have restored Boulle furniture which lived in Hawaii, and I can attest to the problems of salt air on brass. Not a pretty sight.

The third part of the surface is the mastic, which is composed of protein glue and wood dust. This mastic is around all the elements, filling the gap where the saw blade cut away the materials. This mastic is easily softened in cold water, and can be carefully removed using dental tools. It is often necessary to remove the mastic to repair the surface, and replace the mastic after the repair is completed. Unlike wood surfaces, it is fine to apply the mastic from the front surface, since neither brass or shell is porous.

In most cases, I look at the surface and decide if it is easier to remove the brass or remove the shell to restore the damage. The brass is often lifted, bent and distorted, and it is easier to remove the entire element to repair it before gluing it back in place. Missing brass elements will need to be engraved after the repair is completed to match the surface design.

The shell is prepared by boiling in hot sea water for some time to soften it. Then it can be scraped flat on both sides and shaped to the contour of the surface. It is glued with fish glue, colored with red or brown pigment, as necessary, and placed over red or brown Japanese paper to produce the proper color. In some cases, gold leaf is placed under the shell to produce a very exotic look.

To repair and remove the surface requires care and attention. Paper towels are placed on the surface and covered with cold, distilled water. On top of this a plastic film is placed and the worker waits patiently. After a short time the mastic will begin to soften and the water and towels are removed. Now the repair can begin. More detail on this process is found in my 1997 AIC paper, "Current Trends in Conservation of Marquetry Surfaces", which can be found on my Consulting page of my website.

In most cases, the cost of restoration of Boulle furniture which has been badly treated greatly exceeds the value of the piece. It is only for sentimental reasons or pride of accomplishment that these projects are usually attempted. It is a challenge, to be sure, and one of the guaranteed parts of the project is that, once the initial repair is completed, new areas of lifting will appear somewhere else.

Only after all the elements are properly glued in place can the polishing begin.


Anonymous said...

Sounds like...very persnickety work.
Speaking of controlled substances...I suppose you heard of the raid on the Gibson factory. Have you ever been approached to prove your old woods are certified?

Stephen Shepherd said...

That is a lot of work ahead of you. I once restored a Boulle table, much smaller with little damage. I was fortunate to have a small quantity of hawskbill to do the repairs of the missing work. I was young and not much experience, but did use hide glue and yellow brass for the repairs.
Now after nearly 40 years experience, I would turn down another challange like that. Good Luck.


Tico Vogt said...

Merci, but no thanks!

W. Patrick Edwards said...

The C.I.T.I.E.S. act of 1986 which places endangered species on a list of banned materials created a problem. The problem is not that materials were banned for international trade. The problem is that, for generations before the ban, these materials were traded legally and freely. However, since there was no law against buying these materials, there was no reason to keep accurate records. When the act was passed, responsible people began to keep proper records. That does not serve to prove that something purchased in the 1960's or 1970's was legally purchased, so that early inventory became suspect in the eyes of the law. How do you prove you owned a piece of rosewood or Cuban mahogany or ivory for 40 years, when it was traded or purchased for cash and you have no records?

In fact, almost all the furniture in my home is made of Cuban mahogany, since it is from the first quarter of the 19th century. Can I look forward to a future when the SWAT team will show up at my door and take all my antiques away?

I hope that reason prevails. After all, global warming is much more serious than whether Gibson guitars can provide full and accurate papers for a piece of rosewood. What about the farmers in Brazil who burn the forest to make room for cows? What about the fishermen in the Pacific who kill the sea turtles fore their delicious meat and throw the shell back into the sea since it is no longer valuable?

Anonymous said...

you are bloody right, Pat.

Traian Gherga said...

Mr. Edwards, I personaly am a young restorer willing to learn and work hard... I have a question for you: How can I glue the boulle work back into place? I have curved surfaces on a big cabinet and there are a lot of lifted areas...

I am thinking of placing a wet rag and use a heater so I can reactivate the hot glue, use scootch tape to keep everything in place where needed, and also apply a sheet of hot glue on the surface and press with plywood that can mold after the curved form of the cabinet.
I don't have the possibility to use the techniques you described in your article... there are a lot of materials I cannot find in Romania so I need to work "in situu".

Can I use an Iron to glue faster ? thank you

W. Patrick Edwards said...

Boulle marquetry is glued to the surface of furniture with fish glue. This is the only glue to be used. It is very sensitive to heat and moisture, so you need to proceed carefully and pay attention to how it reacts. The shell and metals are not damaged by water, and the shell actually softens and relaxes with the moisture, making it easier to conform to the surface.

The clue to this is the mastic. Look very closely at the mastic, which fills the gaps. It will expand when it absorbs water and that is the time to press it, using heat. DO NOT USE HIGH HEAT! Only use heat which will not burn your skin.

I suggest using plexiglass instead of plywood. Thin plexiglass conforms to the surface and is easy to see through so you can see the work. It also does not stick to the glue.

Fish glue takes much longer to cure, so allow a few days for it to set before you clean up with water. Do not use too much water or the glue will come undone again.

Restoring Boulle furniture is a challenge. Good luck.

Anonymous said...

where can I buy fish glue? Thanks Sam
Jan. 8 2115

W. Patrick Edwards said...

Fish glue is manufactured in Canada and sold by Norland Products, Inc. 2450 Route 130, Suite 100, Cranbury, New Jersey, 08512. It is also sold by Lee Valley Tools.