How to Recognize the various forms of Gilding on Picture Frames

Gilding has been employed in the art of frame making long before the frame was removed from the wall, separating it from surrounding architecture. Gold-leafing, a form of gilding, is the process of applying gold or metal leaf to a substrate. There are several application methods and several types of leaf used to create variations in the gilt finish. Presented here is a cursory overview of leaf types, application methods, substrates and surface treatments with pictorial guides to aid one in recognizing the differences. Though picture frames are used for this presentation, the content applies across most realms of gilding.

Difficulty: Moderately Easy

Instructions

Things You'll Need:

• An interest

1. 
    
   Imitation gold leaf, oil and water sizes, glazed

   Leaf types: Gold leaf ranges in purity from 24 Karats (100% pure gold) to 9kt (49% pure gold) and varies in colour. In karats less than 24, the gold has been alloyed with silver, cooper, platinum or palladium, altering shades and colour. Between 24kt and 21kt, the hues range from reds through yellows. A lemon colour best describes 18kt leaf and 16kt leaf is extremely pale yellow. Karats less than 16 fall into the white golds--appearing more like soft silvers.
   
   Metal or foil leaf has no gold content. The most popular form of metal leaf is imitation gold, aka composition leaf, an alloy of copper and zinc. Imitation gold is more brassy than gold and is available in several “brassy” colours. Copper leaf is fairly common, yet more so in architecture than framing. There are also several variegated leafs available tinted in greens, blues and reds. In the family of silver-tones, there are aluminum, silver and palladium leafs. Aluminum looks much like aluminum, thus is usually glazed or washed for a more aesthetic finish. Palladium leaf looks more like sterling silver and does not tarnish. Silver is as silver implies.

2. 
    
   Aluminum leaf, synthetic water size, stippled wash

   Application methods: Leaf is applied with sizing--sizing being an adhesive. There are synthetic water-based sizes, oil-based sizes and gel-based sizes. Gels are usually employed with the gilding of glass. Commercially available oil and water sizes can be used interchangeably with gold or metal leafs.
   
   Oil-based sizes result in a gilt finish ranging from extremely matte to a soft, low luster. These variations are accomplished by the timing of leaf application within the drying stage of the size.
   
   A synthetic water-based finish has a bit less luster than one accomplished with oil. The synthetic sizes are akin to acrylics in that they become rubbery. This finish can be easily marred and more difficult to patch.
   
   Traditional water gilding is the oldest form of gilding, the most difficult to execute, yet the most brilliant. When burnished, the finish is highly reflective and can have the appearance of solid gold, left unburnished the gold takes on more of a soft, rich matte finish. The substrate is prepared with rabbit skin glue, gesso and bole (or clay). A gilding liquor is brushed on the bole and then the gold leaf is applied. As this article deals with distinguishing between the different gilt finishes, I’ll save the traditional water gilding procedures for another date.

3. 
    
   12k gold leaf, water & oil gilt; aluminum leaf in under tones

   The Substrate: Gilding leafs are very thin--almost unimaginable. Metal leaf can be less than a micrometer, while gold leaf is about 100 nanometers (micrometer = one millionth of a metre; nanometre = one millionth of a millimeter) [1!]. When a leaf of gold is held up to the light one can see through it. Therefore, surface colours on the substrate will affect the hue of the leafed finish. One of the most common colours used is an earthy red, which produces a warm gold finish, while blacks and blues create a cooler gold tone.
   
   Substrate textures or the absence thereof also affect the look of the final leafed finish. Metals, especially gold, reflect light, leaf applied to an absolutely smooth substrate will result in a highly reflective finish. A textured area of the substrate will cause light to bounce and slightly subdue or interfere with the reflectiveness.

4. 
    
   22k gold leaf, water gilt, distressed; imitation gold leaf, oil size; with pearl finish

   Surface Treatments: Semi-reactive metals, all those employed in leafing other than gold and palladium, undergo oxidation and tarnish with exposure to air and moisture. The majority of leafed surfaces are sealed with a varnish or shellac to prevent this from happening.
   
   Gold leaf does not have to be sealed, though often times a gilder will apply dry pigments suspended in a clear sealer to accomplish a desired finish. The semi-reactive metals in the lower karat gold leafs will tarnish over time, yet are often not sealed as they produce a wonderful patina.
   
   Imitation gold must be sealed as it tarnishes quickly and quite ugly. This is another way in distinguishing between a gold leaf and imitation gold leaf finish. Imitation gold leaf is most often antiqued or finished over with glazes, stains or washes to diminish the brassy look or accomplish a time-worn finish. A real gold leaf finish would likely be distressed (rubbed down), revealing coloured bole below the gold in an attempt to accomplish a more time-worn finish.

Tips & Warnings

• Study the pictures included in the article.
• Go to your local museum and study the frames.
• Visit gilding supplier sites, most of them have great pictures of the different leaf types and some even have finish examples.
• Check back for future articles in this series.
• Gilding is addictive!

Resources

• [1!]

[drmargaretjamal]

on 12/31/2008 I am one of those who appreciates attractive picture frames. I have bought pictures because of the frame. This was very enlightening. Thanks. :-)

[01Grandy]

on 12/18/2008 I'm a little embarassed I didn't realize there was so much to it. I had never truly appreciated the frames before. Thank you for sharing!

[Partsman76]

on 12/18/2008 I learned a lot, thanks for the interesting article.