Introduction to Metal Clays
Iron powder, Copper powder, graphite powder and many other materials introduced in this website are also used in making metal clays. That is why I feel necessary to describe what a metal clay is, how is it made and how is it used.
What is metal clay and how different it is from ceramic clay?
Ceramic clays are made of kaolin (a mineral consisting of aluminum silicates).
Metal clays are made of metal powders. Metal clays are used to make fine artistic jewelry and other artistic products. The most common metal clay for jewelry is silver clay. Other metal clays include steel clay, copper clay, brass clay, and bronze clay.
Patinated Bracelet made of copper clay
Contributing Artist: Bernadette Denoux
At this time we do not have any image of iron clay articles to publish here; however, because of lower cost, iron clays are an attractive choice for beginners and students of the metal clay art.
Most professional artists use silver metal clay (SMC) to make precious jewelry products. Some metal clay products are made of two or three different metal clays in order to produce multi-color items such as pendants, necklaces, earrings and bracelets.
When two or more different metal clays are being used in one piece, they must all be compatible with each other.
Ring made of Silver clay
Contributing Artist: Bernadette Denoux
How metal clays are used?
Metal clays are first used to make different products or shapes. They are then left to fully dry. Dry pieces are then inspected for defects. At this stage minor defects may be corrected by sanding or a wet brush. Fully dry pieces will then be fired in a kiln or by using a propane torch. The final product will be a metal object. The process of binding metal particles and forming a solid object is called sintering.
How to make metal clay?
Although metal clays are commercially available online or in art suppliers, some may want to experiment with their own metal clay. A simple metal clay is made by mixing metal powders with small amount of water until a consistent paste or lump is formed. In order to improve or modify the quality of the clay or the final product you may add other materials or use other fluids instead of plain water.
Ingredients, Additives, or Modifiers for metal clays
These are some of the ingredients that can be used to make metal clay and some of the additives that can be mixed with metal clay. The additives may affect the workability of the clay as well as the shrinkage rate and the quality of the final product. All non-metal or non-alloy additives must be able to burn out when the clay is fired.
Only use distilled water or deionized water in making metal clay. The minerals in tap water or well water contain minerals that reduce the quality of your metal clay. Start by spraying or adding small amounts of water and mixing the powder until a lump of metal clay is formed. If you add too much water you will need to spread the clay and give it some time to loose some of its water.
Oils and Essential Oils
Oils can be used as an additive to water based clays or in making oil based clays. Essential oils such as lavender oil are usually preferred because they are volatile, dry fast and smell nice. some oils can also prevent oxidation. Essential oils are often sold in tincture form (solution in alcohol). Many people add olive oil to metal clay. The oil slows drying and improves the workability of the clay. Other oils may work as well. Do not add too much oil to the clay; it makes the clay unworkable and unusable. Too much oil may also reduce the strength of the finished piece.
Glycerin absorbs and hold water or humidity. That is why it is used as an additive to prevent fast drying of the clay. Small amounts of glycerin can also enhance the workability of the clay while making it more creamy. Glycerin can also reduce oxidation.
Some of the additives of metal clays such as starch and glycerin can promote mold growth. Small amounts of vinegar may be added to metal clays to prevent mold. Vinegar is a safe mold prevention substance for metal clays because it can fully evaporate and does not leave any residue.
Some of the metal powders or alloying powders used in making metal clays include Copper Powder, Bronze powder, Tin Powder, Nickel Powder, Iron Powder, Silver Powder, and Graphite Powder.
Binders (starch, CMC, Polyvinyl Alcohol)
Binders are adhesive or glue substances that can keep the petal particles together in a lump or paste. Using a binder increases the green strength of metal clay products. Green strength is the strength of a metal clay product before it is fired. Using binders is required when making larger pieces or when you are using large grain metal powders.
Liquid starch is a water based solution of starch used as a binder in metal clays. You may make your own liquid starch to ensure that it is made with distilled or deionized water. To make liquid starch you must first dissolve the starch in cold water and then heat it up to make a clear solution.
CMC (Carboxy Methyl Cellulose)
CMC is another type of binder that is very similar to starch in terms of chemistry and physical properties. CMS is a stronger binder and a very small quantity of that is sufficient in making metal clays. Unlike starch, CMC can easily dissolve in water.
Polyvinyl alcohol is another water soluble binder that can be used for making metal clays. PVOH 50-42 is a special grade of polyvinyl alcohol that relatively dissolves easier. It usually dissolves in warm water.
Small amount of gum rosin or pine rosin dissolved in isopropyl alcohol may be added as a binder and as a flux to prevent oxidation and to create a stronger bound between metal components.
Ammonium chloride dissolved in alcohol or water may also be used as a flux.
Propylene glycol is another heavy alcohol similar to glycerin that may be used in the mix.
Rubbing alcohol (Isopropyl alcohol) will make the clay more workable. It is also a carrier for other binders or fluxes such as gum rosin and ammonium chloride.
Risks of Making Metal Clay
Making metal clay for the first time can be a challenging task. You may end up wasting a lot of time and materials before getting it right. You may even have problem finding and buying all different materials. Many ingredients of metal clays may be hazardous if not handled properly. It is usually the best choice for the beginners to buy ready-made clay. Commercial metal clays have been extensively researched and tested, and will likely produce more consistent results than a home made metal clay. In making metal clays you will be using metal powders that are harmful if inhaled or ingested. They are also harmful if entered in your eyes or nose. Some other materials are flammable (i.e. Alcohols) or irritant (i.e. vinegar).
Making a Good Metal Clay
The workability and drying rate of the clay depend on the ingredients and mixing process. Metal clay should be easily worked when wet, easily carved when dry, and strong when fired. To create a strong metal clay:
- Use small metal particles, and a mix of sizes.
- Use fully dissolved binders.
- Use as little binder and oil as possible, while still keeping the clay workable.
- All additives should burn cleanly, and ideally be organic/natural.
A bad batch of metal clay may not sinter properly. If it does sinter, it may not be very strong. You may have to experiment with different ingredients and firing schedules for your homemade metal clay. Firing hotter and longer will make stronger clay, but you must stay below the melting point of the metal.
Follow proper safety procedures. Though the ingredients used in metal clay may be non-toxic, the powders can be dangerous to inhale. When working with these powders, you must wear the correct dust mask. Items used for making the metal clay should not be used for food.
- Work in an area with good ventilation.
- When working with metal and non-metal powders, you must wear the correct dust mask. The particles are small and can be inhaled.
- Items used for making the metal clay, such as a blender, should not be used for food.
- Do not mix metal clay near food or food preparation areas.
- To avoid getting the powders in your eyes, wear goggles.
- Some of the ingredients may be irritating; wear gloves when handling the powders.
- Be aware that these powders can also get on your clothes.
- If you have a fume hood (lab equipment, not the fan above your stove), use it when mixing the metal clay.
Check the Material Safety Data Sheet (MSDS) of any unknown ingredients before purchase. Note that products from different suppliers may contain different ingredients and have different MSDSs.
If you use any ingredients that are not organic, be sure you know what chemicals are produced when they are burned. Never breathe the fumes produced when firing any metal clay, even if all ingredients are organic.
All metal clay parts will shrink during the firing or sintering process. The rate of shrinkage depends on the composition of metal powder and the ratio of the binding materials.
The order of mixing can make a difference in the success of your metal clay. This is the recommended order:
- Make a binding gel consisting of water and water soluble binding materials (i.e. CMC and starch) and water soluble fluxes (i.e. ammonium chloride.
- Prepare rubbing alcohol solution (Add pine rosin if needed).
- Mix the binding gel, rubbing alcohol solution and metal powder to make the clay.
- Add glycerin, lavender oil, Water to the mix if needed.
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