HOW DO I GILD IT?
Let me count the ways...
by Grace Baggot
There are many different ways to create a gold finish. To clarify what they are and how they work let us look at gilding from an historical and developmental perspective. There has always been a desire for displaying gold, what has changed is the method. Man_s aesthetic for how he displays his wealth also changes, for fashion or practical reasons.
When the Egyptians began gilding they were not the first to cover an object in gold. Gold foil had been around. What the Egyptians did differently was to disguise the fact that an object was made of lesser quality materials than gold. This made an object look as if it were actually cast in gold, not just wrapped in it. They accomplished this by using a gesso, which is a binder stuffed with a filler like clay or chalk; spreading it on the surface of wood; smoothing it a little; and covering it with gold hammered much, much thinner than foil. The surface looked more like cast metal than like wood and only a smidgen of gold was used. When the wooden chair was carried to the burial chamber, paraded in front of the public, everyone would have sworn that the chair was made of solid gold. This was the birth of the water gilding technique.
Time marches on and Medieval Manuscripts bring gilding to the forefront of fashion. This time it is in prayer books, known as illuminated manuscripts. Illumination is a great way to describe gilding because it is luminous. It is the unique way light has of sliding over a metal surface and uninterruptedly bouncing back that causes it to seem like a source of light. The illuminators created a raised surface on parchment, employing a gesso. Like the Egyptians, they wet the gesso and laid thin leaves of metal on the surface, from whence the name water gilding. The special difficulty for the illuminators was that they did not wet the gesso surface with a brush and water but would activate the binder in the gesso by breathing on it. Not a way to do a chair unless your up to pulmonary gymnastics.
Water gilding in all of its forms is time consuming to produce. The first act is to create a surface on top of the object and then refine this new surface. Once a perfect surface is obtained, the leaf is applied. Well, the industrial revolution really challenged that. The demand for production caused everyone to begin to think of ways to use machinery to assist in creating products to meet a new demand. We became able to produce objects with more refined surfaces and did not need to disguise or correct them so much in finishing. The gesso stage of gilding becomes obsolete in a way, reserved only for works of great quality. The mainstream had begun to employ all sorts of other materials to adhere leaf to surfaces. It is good to refer to these materials as mordants since their natures are so diverse. The most common mordant technique is to use an oil varnish as a size, this is _oil gilding_. The technique is as follows: render the raw surface non porous; apply the oil size thinly and evenly; allow it to dry to the right point if tack (stickiness) and then apply the leaf directly.
Gold leaf isn't very heavy. It takes 1000 leaves of gold to equal 18 grams or attain the thickness of a dime. A mordant need not be very sticky or strong to hold such a material to a surface. Egg white and boiled down beer were often employed. The difficulties were and are a predicable drying time, uniform reflective quality, covering large areas and compatibility to finishing and substrate materials. A linseed oil manipulated with a dryer to dry at a specific time was developed and continues as a quality finish today. All external architectural gilding is done employing a linseed oil size and 23 karat gold leaf of 18 gram weight or heavier.
In this new age of technology we have developed other materials we can use as mordants. There are many different acrylic adhesives on the market that are employed in exactly the same technique as oil gilding. An acrylic binder (usually water soluble before curing and not to be confused with water gilding which is a technique, not a material.) is applied to a surface; allowed to dry to a specific tack and leaf is then directly applied to the surface. These acrylics have been created for use on paper, in architecture, in art and just about anything else you can think of. The assortment of acrylic mordants is large and varied but the technique for employing them all is about the same, though each has its own nuance. Since they are new to the market your supplier should have directions for their use. Acrylic gilding does not offer the harder finishes that other gilding techniques and materials provide. Very often this fact is of little concern.
Just prior to acrylics the spray gun was a wonderful shot in the arm for both water and mordant gilding. Gessos and mordants can be sprayed. Today's framing industries are mixing and matching all kinds of techniques and materials. Fish glue, rabbit skin glue and gelatine, all being water soluble binders, are sprayable. Acrylic adhesives are sprayable too and some of them must be sprayed since they set up so quickly. Spraying does not leave brush strokes, greatly reducing the time consuming task of sanding . Even laborious water gilding is revived since spraying allows for a wet on wet application offering better bonding of layers and speed.
The cutting edge of gilding today is the addition of the computer. Through the plotter, also known to some of us as a printer, a mordant can be fed like ink and printed on plastic (Mylar to be exact) in any predesignated pattern scanned into the computer. This mordant is transferred to almost any surface like a rub and stick applique. No waiting for drying times. The leaf is immediately applied; the excess gold is brushed away, adhering to the mordant and not to the surrounding areas. This is a big breakthrough since detail can be attained quickly and with edges more sharp than stenciling could produce.
When the Egyptians gilded it was to create objects that augmented the appearance of opulence. Up through Victorian times gilding helped dinner parties stay at the table longer. Light bounced around their galleries and dining rooms from frames to furniture to cornices, catching the candle light hundreds of ways and bouncing it back. Today we have lots of ways to produce light. We no longer need to send frames out each year to be releafed for maximum wattage. The taste and demand for gilding is constantly changing but the way a well gilt object plays with light will always be the same, breath taking!