Techniques
This page aims to describe some of the terms and techniques which are employed to achieve the end results described on previous pages.
Cleaning
Cleaning surfaces can be very simple or very complicated and involves more variations and substances of a simple technique than most other operations in a conservation workshop. Anything from saliva through White Spirit, Acetone and Ammonia to a variety of strippers and chemical substances might be used. The substance used will depend on the substance to be removed, the surface to be cleaned and whether or not it is to be preserved or added to. Cleaning processes can also be quite aggressive involving scraping, scrubbing and a variety of abrasive materials. The cleaning of paintings is a complete and specialised art in itself.
Boulle Work
André Charles Boulle was cabinet maker (or ébanist) to King Louis XIV. He devised a technique of inlaying Tortoise Shell (actually from the Turtle) with Brass and Pewter in wonderful 'grotesque' shapes and covering pieces of furniture with them. The shapes were cut with a fret saw, sometimes in pairs so that a pair of tables would have a positive and negative effect, meaning that the areas which are brass on one are Tortoise Shell on the other (see project - Pair of Boulle Card Tables).
Oil Gilding
This is a waterproof surface much employed for its quick and effective end result. The object or area is covered with a slow drying varnish, (or mordant) and when the varnish has achieved the right level of tack the thin gold leaf is rubbed onto the surface . That's it! The most important thing to remember with oil gilding is that it can not be manipulated, distressed or burnished. It has a multiplicity of applications from the railings at Buckingham Palace to inscriptions on gravestones.
Water Gilding
This is a very old process known to the ancient Egyptians and involves covering objects in a thin layer of gold to deceive the eye into thinking that it is in fact solid - the oldest con trick in the world! The process involves a thick plaster layer (gesso) which is designed to be a cushion for the gold. All these layers are made from finely ground earth substances bound together with a refined animal glue (Rabbit Skin glue). The gold is then laid onto the surface with water which has a small quantity of rabbit skin glue in it and left for a minimum of four to five hours. The most important part of water gilding is that the gold can now be manipulated, distressed to match an existing old surface or burnished with a polished agate for new work. This process can be used with Platinum, Palladium or Silver.
Mercury Gilding or Flame Gilding
This process is highly toxic and extremely dangerous and has effectively been outlawed except under highly specialised conditions; it is used to gild metalwork. The process involves kneading gold leaf into mercury until the mercury will take up no more gold. The paste is then painted onto the metalwork. The mercury is then burnt off with a flame, this process produces a poisonous gas inhalation of which can be fatal, but the end result is spectacular.
Marquetry
This process involves the making of pictures out of different types of wood which different colours and grains.
Parquetry
This process is the same as Marquetry but restricted to geometric designs. (See project Steinway Grand Piano 1899).
Cold Casting
This process involves a silicone mould being made of an original work of art; there are specialised resins which are then loaded with bronze powder (that is real metal ground very finely) and introduced into the mould and allowed to cure. The cast is then subject to a variety of patination materials; the metal content of the resin will react and behave like the metal in a hot casting process.
Adhesives
Many different adhesives can be used according to the project in hand - traditional animal glue must be used on all jointed, veneering and anywhere where it has been used before. On 20th century furniture where resin glues (eg Cascamite and Aerolite) have been used, there is a good case for using a glue that is easier to take apart in the future if necessary. Resin glues are best used for large exterior projects and boatbuilding. They are completely waterproof and set like concrete. Ceramics can only be repaired with modern resins. Modern technology has produced some very sophisticated products; the advantages of modern science should be used where possible. Epoxy resins (Araldite) and Cyanoacrylate adhesives have extensive uses.
Rare and Precious materials
With international legislation concerning rare and endangered species, materials such as Ivory or Tortoise Shell are only from old objects already made pre 1947 (in the trade known as ‘break ups’) for replacement purposes. All timber used is either from ‘break ups’ or from sustainable sources.
Ars est celare artem – Ovid – (True art conceals the means by which it was achieved)