Metal Casting Zone Info Blog

Posts Tagged ‘Precious’

I am making a piece of Jewelery and I don’t have the resources to cast silver. However I do have plenty of materials at hand to use. I was wondering if it was possible to cut a larger stone (probably not a gem) into a pendant, and have jewels encrusted in it, and for it to look good? If its possible, what stones would work the best and look the best together?

Precious metal clay (brand names are PMC and Art Clay) is modern-day alchemy. PMC is a clay base with tiny pieces of silver suspended within it that, when heated, burns off the clay leaving a solid silver residue. The clay base acts as a binder for the metal particles. Once this has been removed, the remaining silver particles bind together, giving you the finished product.

The real beauty of precious metal clay is that it can be manipulated like any ordinary modelling clay, making it perfect for jewellery making. The modern precious metal clay can be using a jeweller’s torch, as the firing temperature is much lower than the early versions of this clay. However, a small kiln will produce a much more constant temperature range and can be controlled exactly, meaning that the results will be more consistent.

Precious Metal Clay once had a very bad reputation for shrinkage, making it unsuitable for fine work or detail. Modern precious metal clays have a much lower shrinkage rate (around 10-15%), but you still need to factor this into the final piece to ensure that really fine detail is not lost in the firing process.

Once fired, the silver piece will seem very lacklustre and dull, so it will need finishing. The dull matt surface hides the real beauty underneath, so finishing and polishing will reveal the shining silver below. When soldering finished precious metal clay pieces it is essential to remember that the surface will be more porous than standard sterling silver, so it is best to burnish the piece prior to soldering. But because it is almost pure silver there is little risk of fire stain on the surface and the final results are almost indistinguishable from sterling silver.

Because precious metal clay is a clay, it takes impressions very well. A design can be pressed onto the surface of the clay and be revealed in the final silver piece. Patterned rollers, lace or even leaves can be used to create unique effects that are difficult to reproduce in ordinary silver unless it has been cast. Precious metal clay is a popular way of making silver beads. The clay can be formed into beads, decorated with a surface pattern and then fired in a kiln quickly and easily, producing high quality silver beads.

Safety considerations have to be taken into account when working with precious metal clay because of the high temperatures required to fire the clay. A small enamelling kiln allows you to safely achieve the temperatures required for optimum results, but ensure that you have all the correct equipment such as tongs with heat resistant handles to extract work from the kiln safely and a heat-proof surface upon which to work.

Precious metal clay is an ideal medium to work in if you want to create pieces of silver jewellery that are unique to you. The only thing that limits you is your imagination. Precious metal silver clay is widely available from good jewellery equipment suppliers. There are two main brands – Precious Metal Clay and Art Clay Silver. The clay is also available in other metals including gold, but the cost is significantly higher than the silver clay.

There are many articles on precious metals on the web and some of them are quiet professional with a lot of details and data. I will try not to give you just another one. Here I will offer you a simple version and avoiding extensive technicality add my professional opinion on the best use of these metals in order to utilize their unique properties.

In this article we will focus on the most popular precious metals used for jewelry: gold, platinum and the fast growing in popularity palladium. Pure gold and platinum are soft metals which are extremely dense. pure gold is about two and half times heavier than iron and pure platinum is just under three times. While really bright in color pure metals are not suitable for fine jewelry because of their softness. Soft metals are easy to damage, difficult to polish, and unsuitable for detailed work. This is why they are mixed (alloyed) with other metals, in order to give them the desired properties. This is also where all this “carats” and confusing numbers come into play. In fact it is pretty simple. All pure metals in nature are white or gray in color except two, gold – bright yellow and copper- reddish pink. Now we go back to precious metals. All different colors of precious metals are achieved by mixing these colored metals with white ones.

Carat is a confusing name for purity or fineness of precious metals. It is confusing because the same word is used as a weight measurement for precious stones. That carat is equal to 0.2gr. and have nothing to do with metal fineness. To differentiate the one carat from the other, in some standards, weight carat is marked with ct and purity karat with kt or k. We can accept this rule to avoid confusion in further articles, therefore when we address metal purity we will use “karat”. Karat is used mainly to define purity of gold alloys. Different countries have different standards for gold purity and the most used globally alloys are: 9kt or 375, 10kt or 416, 14kt or 585, 18kt or 750, 21kt or 875 and 22 or 916. The alternative number which alone can be used as hallmark indicates the number of fine gold parts in the alloy out of 1000. The easy way to translate this into a manageable information is to perceive it as the percentage of fine gold used x10. For example 750 means 75% pure gold content or 18kt.

Platinum is used in almost pure form and 95% hallmarked 950 is a standard alloy. All alloys with pure platinum content of 95.0% or higher can be also marked with the full word “platinum” or “”plat.” Other used alloys are 900 (90%), 800 (80%) and 585(58.5) also called karat platinum. The amazing qualities of this amazing metal are better described in another article where I am comparing it with the white gold alternative.

Palladium 950 alloys are as white as the platinum, blending well with white diamonds and eliminating the need of rhodium plating. Palladium is a light metal with weight close to the one of sterling silver and much lighter than platinum and high carat gold alloys, thus making it the metal of choice for items like large earrings. At the time of writing, the price of 950 palladium alloys is about a third of the price of the 18k white gold offering great possibilities for large solid pieces at significantly reduced price. One disadvantage though is that quality casting of palladium requires materials and equipment, currently not viable for small workshops

The hallmarks you will usually find on your precious metal jewelry are:

1). Karat or fineness stamp (e.g. 18kt/ct or 750)

2) Manufacturer’s stamp

The karat stamp does not have much value without the manufacturers stamp because the declaration of purity is not signed. Beware; in most countries you can buy a karat stamp for few dollars.

Variety in gold colors and mechanical properties is achieved by alloying fine gold with one or more other metals. White gold for example is a gold alloy with whitening metals, usually palladium, nickel or silver or combination of them. Since the fine gold is always yellow, it is the alloy (base) metals that give the karat gold its color and properties. For example to be able to stamp an item as 18k it must content at least 75% of fine gold. The remaining 25 percent of alloy metals will determine its color and physical properties. If 8.4% of copper and 16.6% silver is used in the alloy, we will end up with the traditional rich 18k yellow gold color. If we mix the same amount of fine gold with 15 % of palladium and 10% of silver we will have good quality white gold. The constant content in 18k gold alloy is always 75% pure gold. Higher than 18k white gold alloys are not possible because the alloying metals are not in sufficient quantity to absorb the yellowness of the pure gold. 21k or 22k gold is always yellow, very yellow. The same principle applies for platinum and palladium, although these metals are used in much purer form (95% is a standard) and there is not detectible changes in color. The only changes there are in physical properties.

Now, with our newly acquired knowledge of precious metals we will probably arrive at the questions: What are the best alloys? What metal jewelry should I buy?

Different metals are good for different purposes. As a general rule (and if you can afford it) buy alloys with higher precious metal content. That applies mainly for gold, since platinum and palladium are used in almost pure form. 18kt gold or higher have distinctive gold color and real precious metal properties. My opinion is that alloys with less than 50% gold content (under 14k) should not be called gold, but gold brass or something else defining the inferior gold content. If you are looking for big bold and heavy pieces the best is to go for silver with gold accents or the very new precium (25%palladium and silver alloy developed by Handy & Hartman)which may be already on the market at the time you read this article. For your fine jewelry pieces choose 18k gold and platinum. 18k white gold can be used for heavier, thicker pieces while platinum is the best for delicate settings with a lot of detail. It does not make sense to set $10 000 diamond in white gold just to save $ 300-400 difference on platinum setting. Besides the aesthetical superiority, the security of platinum setting is immensely greater. When we come to earrings, especially large ones, choosing lighter alloys is essential. Palladium is the first choice followed by 14k white. For yellow, stick to 18k. You can never get the right color in lower karats. Then, your goldsmith’s ability to work light will come handy. Try to find the right craftsman. It is really making all the difference. The weight of the stud settings is rather small even in the case of large diamonds, thus making the platinum the obvious choice for white metal. The difference in price will be insignificant but the difference in strength and safety and quality – vast. Another advantage of the platinum studs – they could be made very delicate and retain their strength.

Palladium, not to be confused with platinum, is one of a group of white precious metals that can be used for a variety of commercial applications (i.e. computers, mobile phones, dentistry, medical equipment, fuel cells) as well as in the manufacturing of beautiful pieces of fine jewelry. Most palladium today, however, is used in the manufacture of automobile catalytic converters.

Palladium, named after the asteroid Pallas, was first discovered in 1803 by William Hyde Wollaston. Palladium is a rare metal with the largest deposits found in South Africa, Montana, Canada, and Russia.

The first recorded use of palladium in jewelry was in 1939 as an alternative to platinum or white gold. This precious metal provides the contemporary look of a white metal. Unlike white gold, palladium is naturally bright white and its color will never fade. Palladium has a low melting point but becomes very strong when cooled, making it a good alternative to softer white metals. It can be hammered into very thin leaves just like gold, and can, in fact, be used in the production of white gold.

Palladium offers many of the desirable traits of platinum at a terrific price, considered a fashionable, affordable choice for custom jewelry. The metal is 40% lighter, harder and less expensive than platinum and provides a hypoallergenic metal suitable for those with nickel sensitivities.

Until recently, the use of palladium in jewelry has been limited due to the difficulty of casting this metal. Recent advances, however, have produced a new alloy of palladium that is perfectly suited for jewelry manufacturing, offering consumers an ideal substitution for platinum at a reasonable cost. The most common combination of the metal is 95% palladium and 5% ruthenium, known as 950 Palladium.

Palladium settings are preferred over gold for extra large diamonds and gemstones, since the metal is more durable than gold and less likely to incur damage during every-day wear. Many customers who opt to wear their fine jewelry selections daily prefer the lighter feel of palladium. Larger earrings and necklaces made of palladium can be worn comfortably all day.

If you have found that you are allergic to other types of metals, you may find that palladium is just what you have been looking for. It is a hypoallergenic metal, meaning it won’t leave you itching or with a rash where it touches your skin. Since many pierced earring wearers are especially sensitive to some metals, finding studs, hoops and posts that are made of palladium can truly make wearing earrings fun again.

The Chinese have historically been the biggest buyers and producers of palladium jewelry. However, the advances in palladium casting techniques and recent escalation in gold and platinum prices are driving an increasing demand for palladium fine jewelry around the world. The demand is expected to continue to increase as many consumers discover the beauty, durability, and lightness of this lustrous white precious metal. As a result, there is an increasing availability of palladium jewelry in jewelry stores around the world, especially wedding bands and engagement sets, in jewelry stores around the world.

Metal clay is a suspension of tiny particles of metal in a clay binder, which can be used to make jewellery, beads and small findings. The beauty of metal clay is that it can be manipulated in the same way as any modelling clay, but once fired the binding agents are burnt off leaving the metal form intact. Although there is a certain amount of shrinkage (between 10-15% for the more modern versions), very fine detail can be achieved, including impressions that would require casting in any other method of metalwork.

Silver metal clay results in objects containing almost pure silver (also known as fine silver) which is ideal for enamelling. There are two popular brands available – Precious Metal Clay (also known as PMC) and Art Clay Silver (ACS). Precious Metal Clay was developed in the early 1990′s in Japan and consists of microscopic particles of pure silver (or fine gold powder) and a water-soluble binder which burns off during firing. The original formula of PMC (now called ‘Standard’) has to be fired in a kiln at a temperature of 1650F and has a high shrinkage rate of around 30%. Two additional versions were later developed called PMC+, which can be fired at 1490F and PMC3, which can be fired at temperatures as low as 1100F. Both of these later versions of PMC have much lower shrinkage rates, allowing much finer detail to be worked into designs.

Art Clay Silver (ACS) was also developed in Japan and is similar in consistency to PMC+. The main difference with ACS is that it can be fired using a hand-held torch or gas oven. Because of subtle differences in the binder components and the longer firing times, ACS benefited from having a considerably lower shrinkage percentage – only 8-10%. This means that ACS can be worked in more detail without any loss of definition in fine work. Art Clay Slow Dry was introduced soon after, which has a much longer working time before requiring firing, allowing intricate work to be moulded into the clay with no loss of malleability.

Art Clay 650 and Art Clay 650 Slow Dry are now becoming increasingly popular, as not only do they have a longer working time but can be fired at temperatures as low as 650C/1200F. This allows jewellers to incorporate glass and Sterling Silver into the designs without fear of damaging the components. AIDA, the manufacturers of ACS have also introduced Oil Paste, a product only used on fired metal clay or milled fine silver, and Overlay Paste which is designed for drawing designs onto glass and porcelain. These two products have allowed the use of metal clay products to be incorporated into a whole new range of designs and mediums, expanding the potential of this product.

Metal clays allow jewellers to work with a material that is as malleable as ordinary modelling clay but produces fine (almost pure) silver jewellery of exquisite intricacy and beauty. Once polished it has a lustre and shine that is easily comparable to cast silver and because of the development of the products over the last few years shrinkage is now no longer an issue. The type used depends on personal preference as both types have their advantages, but incorporating metal clays into your jewellery design gives you a new medium to explore with beautiful results.