Discover how Stuller’s Assay Lab ensures alloy accuracy, learn the fundamentals of precious metal testing, and explore metal testers designed for today’s bench jewelers.
What happens before a metal alloy reaches the bench? Behind every casting grain, solder, and precious metal product is a rigorous testing process designed to ensure accuracy, consistency, and performance.
To get a closer look, we spoke with Stuller’s senior metals technology manager, Sara Boudreaux, who has more than 21 years of experience in metals technology and analysis. She takes us inside Stuller’s Assay Lab to explain how precious metals are tested, why alloy accuracy matters, and how today’s metal testers help jewelers make informed decisions with confidence.
Sara Boudreaux
Senior Metals Technology Manager
Sara Boudreaux is Stuller’s senior metals technology manager and has been helping advance the company’s metals expertise since 2005. Throughout her tenure, Sara has worked closely with teams across the organization to improve alloy performance, optimize processes, and maintain the highest standards of quality. Today, she continues to lead Stuller’s metals technology efforts, helping ensure jewelers receive materials they can trust.
Each batch of metal produced in Stuller’s melt room is sampled and analyzed to confirm its composition. Whether it’s gold, silver, copper, zinc, or nickel, every element must fall within strict tolerances before production can begin. If a batch falls outside specification, it is adjusted, retested, and verified before moving forward.
This testing happens before fabrication starts, helping prevent issues later in casting, forming, setting, and finishing. Even small variations in alloy composition can affect workability, durability, and appearance. For jewelers, that means fewer surprises at the bench and more consistent results.
The Assay Lab also supports Stuller’s precious metal clean scrap program by analyzing incoming materials and determining their precious metal content. This ensures accurate valuations and reinforces trust throughout the refining process.
Why Alloy Accuracy Matters to Bench Jewelers
For bench jewelers, alloy consistency directly impacts daily work. Metal composition influences how an alloy casts, solders, sets, polishes, and wears over time. Small variations can create challenges during manufacturing and repair, leading to inefficiencies or rework.
By verifying alloy composition before production begins, Stuller helps eliminate variables that can affect performance. Consistent materials allow jewelers to focus on craftsmanship with greater confidence.
The Science Behind Precious Metal Testing
To maintain this level of accuracy, Stuller’s Assay Lab uses several testing methods, each serving a different purpose.
X-Ray Fluorescence (XRF): Fast and Nondestructive Analysis
X-ray fluorescence, or XRF, is one of the most widely used metal testing technologies. This nondestructive method identifies the elements within a sample and measures their concentration without damaging the jewelry.
For jewelers, XRF provides immediate results and is ideal for buying, appraising, intake verification, and quality control. It offers a fast and reliable way to confirm precious metal content while preserving the integrity of the piece.
Fire Assay and ICP Analysis: The Gold Standard for Accuracy
When deeper analysis is required, the Assay Lab relies on fire assay and inductively coupled plasma (ICP) analysis. These methods provide highly precise measurements of precious metal content and trace elements.
ICP technology can detect elemental concentrations at extremely small levels, allowing the lab to identify subtle variations that may impact alloy performance. Together, these testing methods help ensure every alloy meets exact specifications before it reaches production.
Why Trace Elements Matter
Think of an alloy like a recipe. While precious metals make up the majority of the formula, small additions can influence color, hardness, casting behavior, and finishing characteristics.
By carefully measuring and controlling these trace elements, the Assay Lab helps ensure alloys perform consistently from batch to batch. The result is greater predictability at the bench and better performance throughout the life of the finished piece.
Choosing the Right Metal Tester for Your Bench
Watch our metal testing overview reel on Instagram.
Providing everything from quick counter checks to lab-level verification, today’s metal testers give bench jewelers more confidence than ever. Traditional acid testing remains a trusted, low-cost method for basic karat identification, while digital gold testers deliver faster, cleaner results with improved precision. At the top tier, XRF analyzers provide nondestructive, highly detailed elemental analysis — ideal for buying, appraising, and documenting valuable pieces.
Choosing the right tool depends on your workflow, volume, and accuracy requirements. Whether you need a portable solution for everyday intake or a sophisticated system for in-depth analysis, Stuller offers a range of options designed to support your bench with reliable and efficient testing technology.
GemOro® Superior Instruments Assay Lab Desktop XRF Gold & Precious Metal Analyzer
Designed for maximum precision, this enclosed desktop XRF system delivers fire-assay-level results without damaging jewelry. Its advanced detector measures elemental composition with exceptional depth and accuracy, while a fully enclosed chamber ensures zero exposure. It is ideal for high-volume operations requiring detailed, professional reporting, consistency, and peace of mind.
- Lab-quality precision
- Fully enclosed testing chamber
- Detailed reporting capabilities
GemOro® Superior Instruments XRF Gold & Precious Metal Analyzer
This powerful handheld XRF analyzer offers fast, nondestructive testing of gold, platinum, silver, and more — even stainless steel. Advanced silicon drift detector (SDD) technology ensures accuracy, while wireless connectivity and exportable results streamline documentation. Note: Desktop conversion kit is available for added flexibility and safe, efficient bench use.
- Handheld flexibility
- Nondestructive testing
- Wireless reporting features
GemOro® AuRACLE® PRO Digital Gold & Platinum Tester
Fast, precise, and easy to use, this handheld digital tester verifies gold from 8K to 24K and platinum in seconds. With improved accuracy and a durable, replaceable probe, it’s perfect for busy benches needing clean, reliable results without chemicals.
- Fast digital testing
- No acids required
- Verifies gold and platinum in seconds
8-Piece Deluxe Test Acid Kit
A reliable, economical solution for everyday testing, this complete kit includes acids for 10K to 22K gold and silver, plus a testing stone and star plate. This is a staple for purchasing and appraising, with proper handling required for safe use.
- Cost-effective testing solution
- Proven method for gold and silver identification
Comparing Today’s Most Popular Metal Testers
How Metal Testers Help Build Customer Confidence
Whether evaluating estate jewelry, accepting trade-ins, creating custom pieces, performing appraisals, or processing scrap, accurate metal verification supports nearly every transaction a jeweler makes. Reliable testing helps confirm precious metal content before commitments are made, reducing uncertainty and providing a stronger foundation for pricing, purchasing, and production decisions.
Documentation and transparency are equally valuable. Modern metal testers allow jewelers to provide customers with objective information about the materials they are buying, selling, or repurposing. This added level of verification helps support accurate valuations, strengthens trust, and gives customers greater confidence in both the transaction and the jeweler behind it.
From the advanced technology used inside Stuller’s Assay Lab to the tools available for your bench, accurate metal testing plays a critical role in ensuring quality and consistency. Whether you're verifying scrap, evaluating estate jewelry, performing appraisals, or confirming precious metal content before production, having the right testing equipment can help support more confident decisions and consistent results.