Questions submitted by our members and others from around the Artworld...
This month offers a selection of some of the most often asked questions regarding gilding.
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Q. What is 'gamboge' and is it used in gilding? A. Garcinia Morella, a tree from Sri Lanka and South Central Asia, produces a resin we call gamboge. Historically, gamboge has been used together with another resin from South Central Asia called Dragon's Blood to create a glaze over silver or aluminum to give the appearance of 'old gold'. It can actually be quite deceiving to the untrained eye.
Q. How thin is gold leaf? A. There are some variances in the thickness of gold leaf depending upon karat of gold, manufacturer, and whether it is single or double thickness. On average gold leaf measures approximately 1 micron (1/250,000 of an inch), thinner than a human hair. Gold leaf is most often referred to by its weight per 1,000 leafs, the amount equal to a pack of gold leaf, ranging from 16 grams for 9k white gold to 24 grams for 24k, depending upon the brand. Double thick leaf is actually not double but it is approximately 10-20% thicker (we're still talking pretty thin here!) Q. Where does gold leaf come from and how is it made? A. The manufacturing of gold leaf is a process known as gold beating. Most gold leaf comes from such countries as Italy, France, Germany, Australia, England, Japan, and China. Gold beating is an elaborate process involving beating thin strips of gold between layers of plastic sheets, originally made of sheepskin parchment, calves skin vellum, and very fine skin of ox-gut. Any gold leaf less than 24k fine gold is alloyed with silver and/or copper to achieve different shades. 22k Moon Gold for instance is a combination of gold, silver, and palladium. Q. When applying oil size for oil gilding, when do I know the appropriate time to lay the gold leaf? A. Once you have applied a thin layer of oil size to a sealed surface, wait until it dries but is still 'open', meaning the period when it is slightly tacky but able to receive the leaf. There are different drying times for both quick size and slow dry size and they are affected by temperature and humidity and the age of the oil size itself and also whether you have left the lid off the can for extended periods of time. The best way to judge its readiness is to gently drag your knuckle across the drying size and if it 'squeaks', it's ready. At this point, if you are working with quick size, the drying time goes pretty quickly so move efficiently. Q. When oil gilding I use a 3 hour size but I find that even though the can is still half full the size is ready for gilding in about twenty minutes! Am I doing something wrong? A. No, you're probably not doing anything wrong unless you're painting your size on excessively thin. Once a can of quick size is opened its drying time is shortened quite a bit. Slow dry size is often chosen for higher quality work as it can produce a better luster has somewhat better adhesive characteristics, and stays 'open' longer which will certainly address your problem of twenty minute size! However, that said, I have gilded many objects with quick size with good results and the short set-up time can come in pretty handy. In the end it's best to consider both quick and slow sizes as available tools for you to use depending upon the circumstances. Usually, I mix both the slow and the fast dry size together to lengthen the quick drying time but where the gilding can still be done in the same day. Q. What was the method used for bronzing those pie crust frames from the 40's? A. The sometimes used term 'pie crust' frame got its name from the use of compo - a mould making material comprised of hide glue, rabbit skin glue, whiting, rosin - and which was attached around the perimeter of a wood frame and compressed with the fingers as if making, well, a pie crust. A burnishing bronze powder was used to get that deep, solid old bronze look. Most bronze powders today are not sufficiently fine to burnish but I have found a resource from England where this material can be purchased. Other bronze powders can still be used and are widely available from gilding supply houses but the application is a little different. Q. When should compo be applied, before or after the gold leaf and when should it be finished? Also, is there anything special about working with compo? A. Compo, a composition of a variety of materials including rosin, hide glue, and whiting, has been used
since the latter part of the 18th Century as a mold casting material that can be applied to furniture, frames, and architecture for embellishment. It can be either gilded or painted. There are two firms that I am aware of that sell literally thousands of composition ornaments. One is the Decorators Supply in Chicago, Illinois; the other is Bomar.
Compo can either be attached to another surface by steaming the back of the ornament which re-activates the glue. It is then quickly applied to the desired surface. It will stick to either a gilded or non-gilded area. It is best to apply it before gilding or painting it for overall uniformity. However, it can be effectively gilded and toned first and applied to a frame or table and made to appear uniform with the surrounding area with the aid of a wash or at least a good rottenstone buff all around.
If a compo ornament will be directly attached to another surface rather than steam-activated, a small amount of Tite-Bond woodworking glue can be applied to the back. It will hold well, is quicker and less messy. In this case, the compo may be finished first or last; either will work. If the ornament is going to need to be steamed to wrap around the contour of another surface, then the gilding or painting of the compo will need to be done after the ornament has been applied and left to dry until hard again, otherwise you'll damage the gilding during the steaming operation.
Q. What is Verre Églomisé? A. Dating to approximately 250 BC, although named after the 18th c French Picture Dealer Jean-Baptiste Glomy, Verre Églomisé is the gilding of glass, often with engraved images scratched into the gold leaf and combined with polychrome painting, all in reverse on the back of the glass. One example of a project of mine was a glass table top of which I silk screened the floral image onto the glass and gilded over it with 23k gold leaf. Gelatin dissolved in water is the binder used to adhere the gold to the glass. Q. Do you have any idea where the usage of 'Kt' comes from? A. Sometimes spelled or abbreviated as K, Kt, Karat or Carat, the term is derived from the Arabic 'Quirat' which means the 'fruit of the carob tree'. The pods of the tree contain seeds which were used in the bazaars to balance the gold scales.
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April 13
