Lost Wax Casting; Reducing Casting Defects

July 2, 2017

How to eliminate casting defects when casting jewelry.

Almost all jewelry productions worldwide are made via the lost wax casting process. Lost wax casting, while versatile in that it allows you to create small batches and relatively low set up costs per each part, can lead to all sorts of defects. Almost every company casting silver jewelry has experienced bad casts due to shrinkage porosity or incomplete casting fills. While many people have tips and tricks that they find work for them, few are willing to share these with the rest of the industry.

Our good friend Tyler Teague of JETT ResearchProtoproducts, who has acted as a consultant to industry professionals for over ten years wrote such a great articles on this that we felt obligated to share some of his wisdom.

In his article “Fill ‘Em Up” which he originally published on MJSA, Tyler discusses the two extremely important yet little known concepts among casting houses the user of “Risers” and use of “Funneling”. The below excerpts of his original article are re-published with his permission. The original article may be found in it’s entirety at the following link Fill Em Up.


In the below general casting tips, Tyler addresses some of the most common mistakes that lead to casting defects:

Tips for improving fill and casting quality

As a general rule, when casting it’s best to use the coolest flask and metal temperatures possible that will allow for complete fill and good structural integrity. Cool system temperatures will create less sulfur dioxide gas at the metal-mold interface during casting, which can damage your castings in many ways, causing rough surfaces, enhanced shrinkage porosity, and copper sulfides and oxides—none of which is desirable.

To reduce the chances of creating too much sulfur dioxide gas, you must feed the metal in quickly and keep turbulence to a minimum. Here are some guidelines to follow for feeding castings:

1. Feed into the thickest part of the casting. This promotes differential cooling (also known as directional solidification).

2. Avoid or reduce turbulence to a minimum by shaping or aiming the metal stream as it enters the mold cavity.

3. Avoid sharp corners. These cause turbulence and can break off pieces of the investment mold and wash them into the mold.

4. Use the fewest number of feeders possible to fill the casting.

5. Be sure the feeder has a greater cross section than the cross section of the area where the gate contacts the casting (at least 1.25 times greater is safe).

6. Thick areas of the casting that cannot be fed from the main feeder should have another method, such as a riser, to feed them.

The next major concept that Tyler covers that we’ve included into our standard operating procedures is the use of what he calls Risers.

Using risers to improve fill in complicated jewelry castings

I don’t envy the job of a contract caster. With the growth of CAD/CAM for jewelry manufacturing, the industry is seeing an increase in jewelry designs that, while aesthetically pleasing, are difficult to cast successfully. Often uniquely shaped (for example, with lots of thick-to-thin sections) and sometimes quite large (such as big cuff bracelets), designer pieces can be especially difficult to work with when contract casters cannot modify models.

When feeding a casting of any shape or size, you must be mindful of the “thermal center”—the area that cools last and is most likely to incur shrinkage. To eliminate shrinkage porosity, you must move the thermal center out of the casting any way you can. It is a given that since the thermal center is in the heaviest part of a casting, you should attach the feeder to that section to better your chances of getting a successful casting. But this method is not foolproof: When they cut off the feeder, many casters are dismayed to find the thermal center manifest itself as a hole in the part beneath where the feeder was attached. There is a little-known trick adapted from the foundry industry that jewelry casters can use to pull the thermal centers out of challenging castings. It’s called a riser.

A riser’s purpose is to act as a reservoir of heat and feed metal. It is designed to prevent cavities that can occur as a result of shrinkage when the metal cools. They are especially useful when you have multiple heavy sections in a part with thin areas in between them. I use risers because they simply work better than an ungainly network of extra feeders running all around a casting and back to the main sprue. More often than not, extra feeders cause more problems than they solve. They use more metal, make mold cutting more difficult, and simply don’t feed a casting as well as they should. In many cases, multiple feeders actually act as heat sinks; rather than aiding fill, they require more heat to fill or simply prevent complete fill altogether.

Riser Tree Diagram

For instance, in the photo above, your inclination to place the feeder at the heaviest part of the casting—the top of the ring—is complicated by the intricate pattern on the ring top. Placing the feeder at the bottom of the shank makes it easier to cut the mold, but it’s inadequate to pull the thermal center out of the casting. As the casting cools, the shrinkage porosity will occur in the top of the ring, the heaviest part. By placing a riser on this part of the casting, and attaching it to the side so as not to mar the detailed top, you create a pool of molten metal that cools last, constantly feeding the heaviest section of the casting and pulling the thermal center out. Any shrinkage porosity occurs in the riser, which solidifies last.

Finally Tyler discussing Tapering and casting pressure. This is something very rarely considered by jewelry casters , but that can make a world of difference when casting intricate 3D printed parts.

Taper Away

Figure 1

Figure 1 is an example of a typical 3 mm round feeder with a cross-sectional surface area of 7.069 square millimeter  that I see in many casting operations.

Figure 2

Figure 2 is basically the same 3 mm feeder, but its end has been hammered into a flared shape.

Figure 3

Figure 3 is ideal: a larger tapered feeder with a cross-sectional area of 19.635 square millimeter on the large end and 7.069 square millimeter on the tapered end.

When casting at low system temperatures, flaring the feeder is beneficial because it increases velocity (speed and direction) of the feed metal as it enters the mold cavity. As the molten metal is entering the feeder and moving toward the gate and casting, the speed into the cavity (velocity) increases proportionally as the cross section of the feeder decreases. It’s the same thing that happens when a fireman puts the nozzle on the end of his fire hose. The water that would pass through a 4-inch hose at a given pressure in a fixed time interval is now passing through a tapered nozzle and out of a 1.5 inch to 2 inch opening. Since the same volume has to move in the same time, the speed has got to go up a lot. The difference between the figures shown is that the velocity of the metal entering in figure 3 will be about 2.78 times that in Figures 1 or 2. If you can fill the parts about 2.78 times faster, then it stands to reason that you can still fill the parts using lower system temperatures that improve the castings because less sulfur dioxide gas will be liberated.

Going back to our example of the firehose, the velocity change allows the fireman to deliver water to the top of the burning building, not just to the windows of the first floor.

How to save money and improve casting fills

It doesn’t matter whether you are casting large production trees or small ones, using vacuum-assist or simply gravity casting: The use of large buttons is a waste of money. It’s pure superstition that a large button exerts enough pressure on a casting to improve fill. Fact is, the pressure in the flask is relative to depth and not to volume, and only the metal that is directly over the main sprue exerts any pressure at all. Some French guy named Blaise Pascal in the 1600s and a Swiss guy from the 1700s named Daniel Bernoulli described these laws of liquid pressure way back. Read up on it.

Figure 1

Basically, depth rules. In Figure 1, the pressure at all points marked “P” are the same regardless of the shape or size of the container. This means that all that the metal you throw into the button makes you feel secure but serves as little more than a heat source and money drain.

Figure 2a Figure 2b

If you really want a good fill, use a tall main sprue with a funnel-shaped pour basin, as shown in Figure 2; the drop of the metal from the crucible to the bottom of the flask takes advantage of both the kinetic energy gained during the pour and the inertia of the molten mass, leading to a better fill. I prefer to use full-size sprues and flasks when doing this technique to ensure I get those added advantages. The couple of dollars for the extra investment is cheap compared to the cost of the metal for a button or a non-fill casting.


I Need A Jewelry Manufacturer

January 24, 2017






Who are we?

If you need a jewelry manufacturer, then you’ve come to the right place.

American Gemstone is one of the world’s leading contract manufacturers of branded jewelry. We begin

What do we do?

We manufacture your jewelry for you from your sketches, 2D designs, or CAD designs. We produce single pieces, small batches, and large production runs with no minimum order quantities and cater to brands that need a jewelry manufacturer.

Why should you choose us?

We have built our business exclusively around manufacturing jewelry for brands. We do not make or market our own collections. This has allowed us to develop a business model that is quite unique in the industry. Through years of growth and development we have become a market leader in turn around time, both in terms of ‘time to market’ of new products and ‘production runs’ of current jewelry lines.

Our quality guaranty: As a manufacturer for top 10 brands, products that we make appear in department stores and jewelry retailers all over the world. You can find products that we manufacture in Saks, Barneys, Harvey Nichols, Colette, Browns, and Net-A-Porter, to name but a few of the distributors that carry some of our clients products. We exist exclusively to help you grow your brand.

How do we do it?

Technology, skill, determination. Through these drivers we have grown rapidly into one of the world’s leading manufacturers of fine jewelry. Our clients love us, and you will too.


February 9, 2014

When looking for a custom jewelry manufacturer to produce your jewelry line there are a few key points to research.

In today’s world of globalization, finding a manufacturer isn’t the hard part. The hard part is finding the right manufacturer. Your manufacturer will be a key partner and a critical part of your business. Choosing poorly can lead to catastrophe and can kill you company before you even begin to see revenues.

Important considerations:

Manufacturer’s Intellectual Property Agreements:

One of the first things you should examine when evaluating if a manufacturer is the right one for your jewelry line is the manufacturers policies relating to your design rights. The vast majority of jewelry factories primary business is selling their own collections directly to retail outlets. Most of these factories are happy to take up new business, some of them will agree to produce custom designs at very close to cost just to be able to add the new models to their own collections. Many manufacturers in China are notorious for this. For further reading on some pitfalls to avoid if working with a Chinese Manufacturer I strongly recommend checking out the book titled Poorly Made In China, by Paul Midler.

IP Points to consider:

  1. Does the company have a standardized IP agreement that they issue to custom clients?
    1. A good sign that the company in question does a lot of custom branded work is that the company will have a standardized agreement on hand for the protection of client intellectual property. Most reputable manufacturers will not accept client provided agreements as the administrative load of operating under many different manufacturing agreements would not be feasible for any mid-sized operator, so I would not bother hiring a lawyer to prepare one.
    2. Be wary of companies that are willing to accept your own custom agreements (unless of course you represent a very large and well known organization), as chances are high that the company you will be dealing with is a small organization or a startup and plans on subcontracting most of the processes in manufacturing your line. If this is the case you can be sure that whatever agreements you may have on paper won’t be respected as the company you are doing business with will have no way to enforce IP confidentiality with their sub-contractors.
  2. What sort of enforcement options are in place for ensuring compliance to the agreements?
    1. When dealing in the world of international manufacturing, enforcement is a bit of a tricky issue. In many countries, non-resident aliens do not have the right to sue. In some countries the legal process is either prohibitively expensive to engage in, or subject to corruption. It’s important to do due diligence on the juristic framework in place and ensure that agreements are in fact enforceable.
    2. In most cases a contract that includes an arbitration clause is desirable to one that does not. Arbitration awards in most countries are easily enforceable elsewhere in the world and arbitration is standardized pretty much wherever you go.

Manufacturer or Subcontractor:

A very important question you will want to be sure of right off the bat is whether the company you are dealing with is a manufacturer or a subcontractor. There are many small operators who act as brokers to factories in their respective areas. While subcontractors may be able to add some benefit in certain circumstances such as providing an external QC, or by acting as a sourcing agent to inventory and supply a jewelry factory with raw materials that you intend to provide, for the most part subcontractors tend to get in the way of things. If you are dealing with a subcontractor it’s important to make sure you know all of the facts. Make sure to find out who is the factory that will ultimately be producing your goods, what is their relationship with them, what added value will the subcontractor be providing, and what assurances you will have that your intellectual property will be safeguarded by the factory that will ultimately be producing your goods. Never do business with a company that is not up front about its position in the production chain.

Usually it is recommended to due proper due diligence on the company you will be doing business with and ensure they are who they say they are. There are a number of ways to accomplish this:

  1. Request a factory visit: If you are dealing with a large established factory, they usually won’t have a problem receiving clients directly at their factory.
  2. Request a third party audit: There are a number of well known international audit companies that are more then willing to audit your prospective manufacturer for you. The audit fees they charge tend to range between $500 and $2000 depending on how detailed of an audit you require. If the manufacturer refuses a third party audit, then you know something is fishy. A few well known companies that provide audit services in many manufacturing countries are:
    1. Verisio: Verisio audits (inspects) factories and farms for ethical and legal working conditions on behalf of retailers and other organisations. They have been auditing sites for social compliance since 1997.
    2. Beureu Veritas: Beureu Veritas provide solutions in quality, health & safety, environmental protection and social responsibility.

Manufacturer quality and capacity:

  1. A very important question you will want to determine early on in your relationship with a new manufacturer is the size of the manufacturer’s organization. A thorough checkup should provide you with details of exactly what capacity the factory has. You should find out which processes the factory outsources (if any), and how many production staff the factory has.
  2. Jewelry factories with fewer than 10 workers are very small operators. Usually factories in this size range will not have specialization of labor, and as a result quality may vary widely dependent on the skill of each individual worker. If dealing with a small operator a further concern to ensure addressed is assurances of financial stability. Some things to look into are do they own their own premises or do they rent. What kind of work brings them their most revenue? Do they specialize in retail pieces but need some additional work just to cover the down time? A company experiencing financial difficulty is not a company that you want to entrust your productions to. Most of the bigger retailers will request bank references before engaging large scale productions with a factory. (I certainly would not go this far unless the factory in question is likely to know your brand already and there is question of the factory’s solvency.)
  3. If you are planning a scale-able production, an ideal factory size will have more than twenty, but less than one hundred production workers. This is because larger factories tend to give higher priority to their current business then to new opportunities, so unless you hit the ground running with initial orders in the five to ten thousand piece range, you are likely to be deprioritized by a larger company as a small vendor. So long as the factory that you end up dealing with is in the mid-size range, it should be able to scale its operations to meet your volumes as your business grows, as companies don’t become mid-sized operators without an effective infrastructure.
  4. Can your factory provide samples to examine the craftsmanship? While this is usually one of the first questions people will ask manufacturers, it is in fact one of the least important. If you are in the jewelry business you have at least one nice piece of jewelry, whether it was made by you or not. Pieces that the factory has made in the past really have nothing to do with the execution of your design. What’s far more important is to judge the workmanship on an initial sample of your design. If you feel confident the factory that you are dealing with is on the up and up and will be able to meet your anticipated capacity, it is a relatively small investment to let them make a sample.

Manufacturer Pricing:

Prices in custom jewelry manufacturing: What should you expect?

Pricing in the jewelry manufacturing circuit generally falls into two groups, companies that break things down into components and companies that don’t. Companies that break things down into component pricing tend to be pretty transparent. In this case pricing is usually formula based, calculated by taking raw material costs and applying percentage and labor to those components. Usually manufacturers that present their prices this way take fairly low margins and depend on volume business to remain profitable. Many times volume factories will give pricing with slim to no margins to promising new customers in an attempt to win their long term business. Attempting to negotiate prices before developing a substantial business relationship with the factory risks demonstrating to the manufacturer that you are unfamiliar with industry pricing which can deprioritize your business.

As a general rule, when considering a jewelry production, you should try to stay away from manufacturers that do not break down their invoices into component pricing. These tend to be smaller operations that make significant portions of their income on retail sales.

  1. Manufacturer MOQ’s and development fees:
    1. Jewelry manufacturers generally operate on one of two basis, either they offer free development with minimum quantity orders (MOQ) or they charge a development fee for your masters and molds.
      1. Minimum Order Quantities (MOQ’s): Whether or not the factory charges a development fee, most factories will have MOQ’s which is the minimum number of a product that they are willing to allow you to order. It is very important to get this in writing and to know whether or not a factory’s MOQ is in contradiction to your plan of business.
      2. Development fees. Development fees can be classified into two categories, design fees and prototyping fees.
        1. Design fees are typically charged for either hand or CAD design to produce a factory useable design schematic or a CAD file that can be fed to a 3D printer for rapid prototyping.
        2. Prototyping fees generally deal with the construction of production devices. Typically this is either a set of a master and molds, or a stamping or traveling die. Prototyping fees can vary widely across the industry along with design complexity. Typical development fees can range anywhere from thirty to five hundred dollars for masters and molds, to many thousands for stamping or traveling dies.
      3. Be wary of any factory offering free development with no MOQ. Factories aren’t charities, and a great deal of time and money goes into developing a product. I would make sure you have crystal clear confirmation that you have exclusive rights to any designs you develop along with ownership of any production devices used to produce those designs and any works derived from them before proceeding with any factory offering “free development”.

A few last questions you may want to consider in your search for the right factory to produce your jewelry lines are:

  1. What are the manufacturer’s policies for defective goods and repairs?
  2. Is the manufacturer willing to stock your stones or components for use in your jewelry?
  3. What kind of taxes apply to imports from the manufacturer’s base of operations?

Finally, try to remember that you are trying to convince the factory that they need your business as much as the other way around.

Where to look?

Start with American Gemstone Group. We host this forum, but we really are the best by miles.

For other reference points, many of the companies that you would want to entrust your designs with will have an internet presence. As with most searches in today’s era, the first place to look is google.

Many jewelry factories will also maintain a presence at some of the larger trade fairs like JCK New York and Las Vegas, HKTDC Hong Kong Jewelry shows, and the Bangkok Gem and Jewelry Fair in Thailand. If you are in the jewelry business and haven’t been to any of the above mentioned jewelry fairs, I strongly recommend visiting at least one of them at the very least to examine the market. Be wary of companies displaying large collections of jewelry at the shows. These companies rely primarily on wholesale direct to stores and are essentially in the same business as you.


January 12, 2014

The first step in developing a commercial line, like many things, is clarity of vision. It’s very important for jewelry designers to know exactly what they want to produce and to be able to communicate this vision efficiently. To accomplish this, jewelry designers will need one of four things: A master, a sample, a picture, or a sketch.

A master: A jewelry master is a device used to make a production mold of a jewelry design. A master is usually made out of silver, copper, or brass and acts as a blank template for production. Jewelry designers that have already been producing their designs and are shifting their production to a new factory should make sure they get masters back from the production company in addition to molds. The master is the heart of a design and is what enables a scale-able production to occur. The molds have a limited production lifespan and as they wear out a factory will never be able to replicate products exactly without the original masters.

A sample: A sample or prototype of a design is a piece of jewelry that is an exact replica of what the jewelry designer is striving to produce. Sometimes replicas will use cz’s instead of gemstones or be done in different materials, finishing, or plantings then the desired final piece.

A pictudesign-from-picturere: When providing pictures to work from, a good practice is to overlay any desired dimensions directly onto the image. Usually multiple views are desired to ensure the gold or silversmith will understand the desired side and back views as well. It can be expected that the jeweler working on the piece will take liberty with anything that not specified.

A sketch: When providing a picture, it’s almost always a good idea for jewelry designers to take the extra time to draw out multiple views and overlay dimensions directly onto the design. The most important thing to consider when drawing a sketch is that a jeweler can only be as accurate as the information presented them. The less details provided, the more artistic freedom the designer is giving the jeweler.

When providing a picture or a sketch, it’s important to consider the following:

Main Material: What Material is the design intended to be produced in? (Examples are 18K Gold, 14K Gold, Silver 925 etc…).

Finishing: What kind of finishing is intended on the surface of the design:

o   High Polish – Polished to a near mirror shine.

o   Satin-Brushed (Textured surface; composed of very delicate lines resembling cats hair)

o   Sandblast (Textured surface; Surface will resemble very fine sandpaper.)

Stamps and Logos

  • Where should the purity stamp and logo be located? It’s usually a good idea for designers to specify this, otherwise the jeweler will decide and the result can be unpredictable.
  • If a logo includes text designers should be sure to specify the font.


o   To prepare an approximate estimate of a jewelry design using gemstones, the manufacturer will need to know the color, quality, size, shape, and number of pcs of each variety of stone used in the design.

o   Types of gemstone settings. (Prong, bezel, flush).

o   Should the backs of gemstone settings be open or closed. If they will be open, will they be simple circles or should the jeweler use square patterns. It’s usually a good idea to open the backs of settings, otherwise the stones can appear dull, especially after the pieces have been worn, soap and crud can get trapped underneath the stones.

o   When requesting a factory to make proposals regarding gemstone requirements, Jewelry designers should supply specifics so that the factory can propose something within certain parameters such as a gemstone of a certain color or a certain budget, make sure you indicate all of requirements at the get go. Manufacturers do not like to go back and forth with proposals! Designers should never be afraid to talk about budgets. 


  • Ring Sizes: It’s important for designers provide the desired size of the sample ring, but also indicate what sizes the ring will be offered for sale in. It may be necessary to make multiple masters if it is a design that is difficult to resize due to gemstone placements or pattern details.


Pendants do not generally come together with chains when they are ordered from a manufacturer. If a pendant design is intended to be sold as a necklace, it’s important for that the following is specified:

Chain Type: A catalog of some common chain styles can be found at www.gemwares.com/CHAINS.pdf. Chains are usually produced by specialized chain factories are always subject to availability. Chains are produced in large quantities and then stocked for productions, so it’s usually a good idea to maintain some flexibility when it comes to chain styles. It’s also a good idea to indicate to the manufacturer when a chain style does not need to be exact so that they may suggest more easily available alternatives should the desired chain style be unavailable.


Gold chains styles tend to be more limited in selection then silver as manufacturers usually have to purchase and stock many hundred grams at a time, so are usually reluctant to offer many varieties to clients unless they are will to pay to stock them.

Chain Length: jewelry designs should include the desired chain length in centimeters. (1 inch = 2.54cm). Jewelry designers often forget to include details of any extender chains or logo tags required. This is very important to indicate as it will significantly effect the price of the chain.

Clasp Type: Designs should also indicate the type of clasp that should be used, common styles of clasp are lobster claw and round spring clasp. A catalog of some common findings can be found at www.gemwares.com/FINDINGS.pdf.

Just like chains, findings are usually produced by specialized factories using automated equipment, so custom spring clasps are usually not available except if very large quantities (as they require the manufacture of a specialized machine to produce them). This said, many manufactures will produce custom non-spring clasps like T-Clasps and S Hooks. If a custom clasp is required, make sure to include detailed drawings or images of the desired clasp together with dimensions.

A few last points to consider:

What are the best target price points?

Jewelry Designers should always consider price points when generating designs. A lot of newcomers to the business are slow to discuss pricing, preferring instead to wait for offers so that they may evaluate competitiveness. With a good manufacturer, this is a mistake. It’s important to be up front about key price points to make sure that designs can be made for the target market. If it can’t, it gives the manufacturer the opportunity to provide alternative options so that it can be made in the target price. It will save a lot of wasted effort dealing with these issues up front rather then after development of a sample that isn’t within the budget of the target market. For more on pricing see our article on finding a manufacturer to produce your custom jewelry line.

Designing jewelry with semi-precious stones: What kinds of materials are available?

When developing jewelry designs that will use materials unlikely to be stocked by a jewelry factory in their normal course of business, it’s important to consider the regular availability and consistency of materials. This doesn’t apply only to semi-precious gemstones, but also to unique components like watch crystal, or leather. As a general rule of thumb, jewelry designers that are planning on using any non-standard components or irregular gemstones, should be prepared to pay a stocking fee (which could amount to the cost of several hundred pieces of the component). The time to market will probably also be much longer as the factory will have source hard to find to components. If the exact component isn’t critical to the design, designers should always tell the factory that so that if there is a much easier to find alternative they can offer it!

Designing for comfortability: Just because it can be made, doesn’t mean it can be worn!

Before submitting designs for manufacture, designers should consider how the piece will be worn. If it’s an earring make sure it’s not more than 15grams or so. If it’s a ring, make sure it’s not too wide to be comfortably worn. When you’ve finished your jewelry design taking into account all of the above, visit http://www.gemwares.com/website/jewelry-design/ to have your design produced.



Customer Success Manager

American Gemstone: The World’s Jeweler



December 10, 2013

A common question that we receive is how may I protect my jewelry designs from being copied and reproduced by others. American Gemstone Group guaranties that any products that we produce for our jewelry production clients will never be reproduced by us except at the direction of the client. Once your products are on market though, other brands will start to see your ideas, and if something catches on, chances are somebody somewhere will copy you.

When it comes to protecting designs there are really only two avenues; applying for a design patent through the US Patent and Trademark Office (www.uspto.com), and/or trademarking your name and logo.

A design patent has a few drawbacks:

Firstly, it must be unique by a very specific definition. Many simple and classic designs do not fit this definition.

Further designs registered in this way are only protected for 3 years, and the process will run into the thousands of dollars if a lawyer is involved. (Without a lawyer the registration costs are in the hundreds, however the paperwork and formatting is intimidating to say the least).

A trademark offers protection of your logo, and is very enforceable. This also can be renewed indefinitely.  The drawback is unless the design itself incorporates your logo, it is not protected. If your trademark is simply put onto the piece of jewelry somewhere, it is easy enough for another company to copy your concept and apply their own trademark.