2010 Presentations

One of the most difficult aspects of working with mokumé gane is the fragile nature of the initial diffusion bond. It is well known among the practitioners in this field that if a laminated billet survives reduction to 50–60% of initial laminated thickness, it can be treated in most respects like any other wrought product. The vast majority of billet failures occur during this reduction process. Much effort has been put into developing procedures to allow for successful reduction of laminated billets, but failures still occur.

The purpose of this paper is to begin to examine the role of grain size and growth on the mokumé gane diffusion bond and to try to assess what impact variations in grain size have on the success of billet reduction. We will examine grain growth at various lamination temperatures in the bulk alloys used in these tests and then compare that with grain growth in laminated couples in and around the diffusion zone with metallographic analysis. We will report on the results of testing these laminates in the shop.

A thorough knowledge of the microstructural properties of alloys for jewelry applications is always needed both to set up the proper working processes, such as work-hardening or thermal treatments, and to understand the causes of defects that sometimes occur. By means of optical metallography, a basic knowledge of the microstructure is achieved.

The present work describes the methods for the metallographic examination of platinum alloys, which need specific procedures of chemical and electrochemical etching. It will focus on different kinds of platinum alloys for jewelry after both investment casting and work hardening. Some platinum alloys used in different industrial fields will be considered as well. By comparing different microstructures, it is possible to achieve a deeper knowledge of the metallurgy of these alloys and to identify the correct working procedures, particularly the thermal treatment.

Since optical metallography is just the first step toward the study of microstructures, the analytical potential of other techniques, such as the traditional scanning electron microscopy (SEM) or the transmission electron microscopy (TEM)—the latter used with specimens prepared by focused ion beam (FIB)—will be briefly described. These techniques can be used to complete the interpretation of the data given by metallographic analysis..

The search for new 925 silver alloys for investment casting has intensified in recent years, driven by often competing demands of jewelry manufacturers hoping to improve surface quality, minimize defect rates and reduce costs. Unfortunately, there is no magic bullet, so jewelry manufacturers need to understand the various alloying additives in order to be able to make an informed decision about what alloy is best for their production.

This paper will explain the need for a portfolio of different alloy compositions so that the particular sets of requirements for the product designs of different manufacturers can be satisfied. The pros and cons of different alloy categories, especially silicon-free versus silicon-containing alloys, will be explained. Topics covered include shrinkage and gas porosity, reactivity with investment, form filling, hardness, as-cast trees, brightness, firestain resistance, tarnish resistance, hot cracking resistance, crucible residue formation, user friendliness, reliability, and productivity. Selected case studies carried out on customer items will illustrate suitable casting equipment settings and casting process parameters for obtaining high-quality outcome.

The presentation will build on our research into the production of Japanese irogane alloys (shakudo, shibuichi etc) and their patination using the niiro patination solution, examining solution ingredients and their effect on colour, the application of electrochemical methods to enhance the process, the durability of surface patinations, and the use and effectiveness of protective coatings.

The presentation will address problems of reliability with regard to the composition of the solution and the achievement of even surface patination, as well as the protection of the patinated surface with coatings. The research enhances the understanding of Japanese metalsmithing techniques at both a scientific and a workshop level. It provides solutions to the problems faced by contemporary jewelers and metalsmiths working with these materials, while also widening the area of possible applications.

Platinum is a challenging material for casters because of its physical properties that result in possible crucible and flask reactions during melting and casting, high shrinkage porosity, and difficulties in filling of filigree items. This paper describes a collaborative research effort of several industrial partners and FEM on the influence of casting process parameters, initiated and financed by PGI.

Based on an analysis of casting defects from industrial practice, experiments at FEM were performed in order to identify optimum casting parameters. Two common Pt alloys (95Pt5Co and 95Pt5Ru) and four different investment materials were used for casting experiments with variation of atmosphere, casting and flask temperature, tree design and centrifugal machine parameters. Detailed sample investigation found shrinkage porosity and surface defects as main problems. Optimized process parameters for heavy and filigree items were identified. Future research on platinum casting should focus on casting simulation in order to reduce experimental efforts and costs.

This presentation is tailored toward a general and technical audience in the field of jewelry design and manufacturing to introduce the basic concept of hardness, from the atomistic to the macroscopic point of view, to show how materials behave during hardness testing. Compared to other mechanical testing techniques such as tensile-loading and beam-bending, hardness testing is simple and repeatable as well as time-saving. Because most tested samples can be used afterward, this economical technique has been adopted by jewelry manufacturers and researchers as a way to benchmark and to ensure a material’s quality.

Currently there are many scales and protocols available for a wide variety of materials covering different hardness ranges from soft polymers to super-hard materials. Some of the hardness numbers and values from different scales may be compared directly, but most comparisons must be done with great caution. The focus here will be on accepted hardness techniques for metals and the jewelry manufacturing industry.

The latter part of the presentation will emphasize recent research results showing how to engineer the alloys to increase or decrease hardness. Key mechanical properties such as yield strength, stress-strain relationship, and fracture toughness will also be discussed along with approximation techniques which can (or cannot) be linked directly to the hardness values.

This presentation will provide a brief description of powder metallurgy, the science behind PMC®, and the anecdotal history of its influence on the jewelry industry. It will draw on photo-micrographs, test data, and results of market survey information to provide attendees with a rich and balanced summary of the subspecialty of metal clay. Short videos will provide understanding of the process of working with metal clay, and examples of the exceptional work being made by artists around the world will convey the breadth of influence this revolutionary material might have on the future of the field. Attendees will leave this presentation with:

• a clearer understanding of powder metallurgy in its non-industrial role
• a practical and visual understanding of how clay is used and how it compares to traditional methods
• an overview of the development of metal clay, from early experiments in Japan to marketing and community development in the United States and the subsequent creation of base-metal clays, entrepreneurial endeavors, and professional educational organizations.

Liquid phase diffusion (‘torch fired’) is a method of producing mokumé gane using simple equipment available in nearly every shop, regardless of size. This method allows for quick production of small billets but has been thought by some to produce an inferior material because of wide, ‘muddy-looking’ diffusion zones.

This paper will detail the process of manufacturing liquid phase diffusion-bonded billets and will compare the material with solid state diffusion-bonded material. This will be accomplished by manufacturing rings using identical procedures after the billets are bonded. and examining them using methods ranging from visual inspection to micrographic photography to ascertain if differences in appearance do exist. Portions of the bonded billets will also be tested for bond strength against solid state diffusion-bonded material.

Metallographic etching has been an analytical tool used by metallurgists for well over 100 years. Polished surfaces are etched, which involves using a strong acid or reagent to remove material from different surface features at different rates. This reveals the grains, phases, and defects of the sample when viewed under a microscope. If these features, such as grains, are allowed to grow large enough through an annealing treatment, etching can make them starkly visible to the naked eye. This ‘aesthetic etching’ process is used on aluminum medallions to create a surface that looks like a layer of shiny silver over a dry, cracked desert. The University of Wisconsin–Madison has developed this technique to make jewelry items such as its “EnginEarrings.”

Jewelry that showcases these aluminum medallions combines precision science with stunning beauty and is marketable to engineers and socialites alike. This paper will review the science of metallographic etching and present processes to apply this aesthetic property to jewelry manufacturing applications.

One of the most important aspects of the casting process is related to solidification behavior and the ability to continuously feed the component during its solidification. Proper component design, tree dimension, feed sprue dimensions, additional feeders, component and investment materials, wax burnout, overall processing, etc. are all of critical importance to casting quality and defect prevention. In the jewelry field, mainly due to complex shape of the components, it is, however, not always possible to follow all the casting recommendations.

This study is concerned with creating an additional thermal profile on the mold material in order to provide an externally induced solidification orientation. This effect is possible due to the thermal behavior of the mold material. This work provides a statistical study carried out at an industrial level with hundreds of components, where it is demonstrated that the thermal profile may substantially reduce solidification defects (shrinkage porosity). It also demonstrates the ease of implementing this casting process.

How important is comfort at the jeweler’s bench? Can something as basic as climate control or lighting affect the performance of a jeweler? These are only a few of the questions that will be answered in this paper on ergonomics and efficiency at the jeweler’s bench.

We start by analyzing the bench jeweler’s work environment and offer suggestions and solutions to improve its design. The structure of the bench and seating design is compared to jeweler anatomy and posture. Aids in organizing tools are covered as is a selection of specific tools that will lessen stress on the jeweler’s body. Checklists and suggested improvements bring us to the conclusion and answer the question, “How can we improve workmanship, speed and efficiency by revamping the jeweler’s bench?”

A durable and invisible coating that can be applied to silver to prevent tarnish has long been sought by jewelers and silversmiths. This paper will introduce Atomic Layer Deposition (ALD) as a means of applying just such a thin-film layer on silver. Traditionally, ALD has mainly been used in the semiconductor and display industry, but its capability to produce pin-hole free and highly conformal thin film coatings even on complex-shaped objects is highly applicable to silver jewelry. This paper will explain the process and compare it to other coating technologies such as physical vapor deposition (PVE). Pre-process preparation steps will be discussed as well as coating cost and durability.