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An Introduction to the Material, Tools, and Techniques of Working with Accent Gold for Silver™ What is AGS? Accent Gold for Silver™ provides a means for adding 24K gold layers to silver. AGS consists of microscopic particles of 24K gold mixed with an organic binder. The mixture is dry when packaged, and the artist adds liquid to prepare a creamy paste that is applied and fused to articles made from sterling silver, Argentium™, and fine silver. When heated to a high temperature, the binder burns away and the gold particles combine by sintering to form a solid layer that can be burnished, brushed, or polished to the desired finish. Adhesion to the silver is ensured by a metallurgical (diffusion) bond that forms during firing. AGS provides a gold layer that is many times thicker than electroplated layers and is thus much more durable. The information provided below shows how AGS is used. History AGS was developed by Jewelry Material Innovations, Inc. (JMI) in 2003 to provide jewelry artists with an economical means for adding gold to silver articles without the need for soldering and electroplating. JMI labs produced a 24K gold powder consisting of extremely fine microscopic particles. The very small size of the particles is essential to proper sintering and bonding of AGS to silver. The other ingredient is a resin-based binder intimately mixed with the gold powder. To use AGS, several drops of distilled water and glycerin are inserted into the plastic container and gently swirled for a minute, until the mixture becomes a creamy paste. After firing, the water, glycerin, and binder have completely burned away to leave a pure gold layer. How Does it Work? At the proper firing temperature, the particles of gold combine into a solid mass by a process called sintering. The particles coalesce and the internal voids disappear. Simultaneously, the gold adjacent to the silver diffuses into the silver, and vice versa, which results in a strong metallurgical bond that ensures excellent adhesion of gold to the silver. To avoid formation of fire scale on sterling silver and Argentium™ during firing, these alloys must first be depletion gilded. Standard methods can be used, and information on depletion gilding is provided at the end of this article. Surface Preparation (Reference: Accent Gold for Silver2™ Application and Firing Instructions, ©2009 Mardel Rein) Prepare the surface to receive AGS according to the metal used: • Fine silver: Apply a satin finish or pickle to bright white • Fired silver clay (PMC, Art Clay Silver): Apply to a white, freshly fired surface or pickle to a bright white. • Silver clay green ware: Do all pre-fire finishing. Clay can be dry or partially dry. • Sterling silver: Depletion gild to a bright white. • Argentium™ sterling: Depletion gild. AGS Preparation Remove the shrink wrap from the container and tap the container on a hard surface to gather the gold powder at the bottom. Add 12 drops of distilled water and 4 drops of glycerin (available at drugstores and cosmetic stores) to the powder using the provided dropper. Mix the contents by swirling the container and agitating back and forth. When completely mixed, the material is a brown blob. Light patches indicate non-wetted gold, and if present agitate until they are incorporated. Use a wetted #3 Sable paint brush to stir the mixture and test the consistency. Aim for a creamy, smooth consistency, not runny. If the mixture is too thick, add one drop of water at a time and stir with the paint brush. If it is too thin, allow it to sit open for several minutes to evaporate some of the water. You will learn the ideal thickness of a coat by experience. Application Accent Gold for Silver™ can be applied with a paint brush, clay shaper, or any other tool that you deem suitable. Paint, draw, daub, or drizzle it on. For broad flat areas, daub or paint using a #3 Sable paint brush. For drizzle designs or to draw, use a clay shaper; a chisel edge works well. Apply in one even coat, then dry in warm air for at least 30 minutes. A vegetable dehydrator or ordinary hair dryer works well. Do not place the piece on a hot surface because drying must be done slowly, otherwise the gold layer may not bond properly to the silver during firing. After the first coat has dried, apply a second even coat and dry as just described. The gold should be applied sufficiently thick that the silver cannot be seen through the dried gold layers. However, if the gold is applied too thickly, it may fail to bond properly. The combined two layers should be about as thick as two sheets of paper. Make sure the edges of the gold design are sharp and crisp. Where the material is not thick enough, it will partially alloy into the silver and appear very pale. If the material puddles in crevices, spread it out for an even coat. Firing
Torch Firing: Fine
Silver, Silver Clay Greenware, Sterling and Argentium™ Silver Kiln Firing: Silver Clay Greenware Place items on a kiln shelf and insert into and remove from the kiln while it is at its target temperature. Use a firing glove and long tongs for fast insert and removal. Fire the item for 20 minutes in a pre-heated kiln at any temperature between 1110F and 1650F. Finishing It is important to compact the fired surface very well, and a curved burnisher works well for this purpose. 24K gold is very soft and easily abraded, so burnish gently. After compacting or burnishing the surface, provide the desired final finish by polishing, buffing, tumbling, etc. Do not use abrasives or files, use only polishing grits. Tips for Success • Accent Gold for Silver™ is best used on smooth, flat, or low relief surfaces. It is difficult to burnish tight regions after firing, so textures with fine lines are not a good choice for using AGS. • Stick-on templates can be used as a mask to apply AGS in intricate patterns and designs. For best results use the template on a flat surface and burnish to seal the edges. Apply AGS in two even coats. After the second coat has dried, peel off the template over a piece of clean white paper to catch the bits that flake off the template and return these to the AGS container for reuse. The pattern will detach cleanly and leave dried gold ready for firing. • For metal clay greenware, follow the manufacturer's firing schedule for the clay being used. If it can be properly sintered in 20 minutes at any temperature between 1110F and 1650F, it is a good candidate for co-firing with AGS. The longest, hottest firing recommended for co-firing AGS on silver clay greenware is 20 minutes at 1650F, which provides good strength without excessive interdiffusion of gold and silver. If a longer firing time is desired, fire the silver first and then add Accent Gold for Silver™ to the freshly fired surface and torch fire for 2 minutes or kiln fire for 20 minutes at 1110F. Firing beyond 20 minutes will result in excessive alloying of gold into the silver, but if the firing time is too short the bond will not be complete. Storage • Keep the jar tightly closed when not using to keep the product hydrated. If the AGS is not used regularly, check the moisture content periodically and add a drop or two of water to keep it hydrated. • If the material dries out completely, just add a couple drops of water and allow it to sit for awhile to rehydrate. A clay shaper works well for scraping the sides of the container because the material does not adhere to it. Allow the gold to dry on the clay shaper and then scratch the bits back into the jar. • Add any bits of dried gold from a brush or any other tool back into the AGS container for reuse. Pickling and Depletion Gilding Instructions (Reference: Accent Gold for Silver™ Pickling and Depletion Gilding Instructions, ©2009 Mardel Rein) Before applying Accent Gold for Silver™ to silver and silver alloys, the surface must be cleaned thoroughly and pickled. For sterling silver and Argentium™, the metal must also be depletion gilded. A traditional pickle is sodium bisulfate solution. Sodium bisulfate is corrosive, and it requires special handling and disposal because it is toxic. This solution should be used hot but not boiling. A safe alternative to sodium bisulfate is a natural product such as a citric acid or vinegar and salt pickle. A vinegar/salt pickle can be prepared by adding a teaspoon of table salt per cup of strong white vinegar. Natural pickles work best at boiling temperature and must be watched to keep them from boiling dry. Citric acid-based pickles tend to work quickly on silver and silver alloys. Depletion Gilding Sterling Silver Traditional sterling silver contains copper that forms oxides when heated. In addition to causing undesirable firescale, it creates a layer to which AGS cannot bond. The copper must be removed from the surface by depletion gilding to create an enriched layer of fine silver. The steps described below produce a heavy layer of fine silver for bonding to AGS. Depletion gild as follows: 1) Heat the metal with a torch until the surface is gray or dark gray. 2) Soak in the pickle solution until the oxidation disappears1. 3) Rinse in clear water. 4) Repeat the cycle of heating and pickling until the metal no longer darkens when heated. 5) Pickle one last time, then rinse in clear water and allow the piece to dry without disturbing the white surface. If the item still has traces of oxidation after five minutes in the pickle, clean it with a brass brush and soapy water and then continue the heating/pickling process. A sodium bisulfate pickle will take five or more heat/pickle cycles to gild the surface sufficiently. A vinegar/salt pickle will also require five or more cycles. A citric acid pickle will require three to four cycles to gild the surface sufficiently. Cleaning and Pickling Argentium™ Silver Prepare a batch of pickle according to the manufacturer's directions. Clean the metal with a brass brush in warm, soapy ammonia water (hot water with some dish soap and ammonia added to it). Heat the item to a dull salmon color, then air cool (do not quench in the pickle) and soak in the pickle until the surface is opaque white. Rinse in clear water. Air dry, and do not disturb the pickled surface. Cleaning and Pickling Fine Silver If the article is finished and polished silver clay or fine silver, heat in a kiln to 1650F for 10 minutes to remove the finish and create a clean surface without pickling, provided that there is nothing to preclude this process such solder or a heat-sensitive embedded stone. Freshly Fired Silver Clay If the article is freshly fired silver clay, do not disturb the clean white surface. Apply Accent Gold for Silver™ directly to the fresh surface with no additional preparation. Note that AGS can be applied to unfired silver clay and then co-fired. Pickled Metal Handling Do not touch metal in the areas to be embellished with AGS because finger oils prohibit complete bonding.
Ronald Diegle, PhD |
