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Jewelry QC: Casting, soldering and glue assembly

by John Niggl

Have you ever spent a significant amount of money on an item of jewelry only to be ripped off by poor quality materials or workmanship?

Jewelry QC requires precision and a trained eye.Whether you buy jewelry for resale,  investing, for giving to someone else or for when you just feel like treating yourself, you know how expensive it can get. Jewelry is a luxury good, and nothing takes away more from its value than a quality defect like a crack in the metal casting or soldering. All of us at Quality Wars want to make sure you’re getting what you pay for, especially when it comes to a product that demands such a high cost and precision to manufacture – not to mention jewelry often gathers sentimental value over time. How would your great-great grandmother’s engagement ring be passed down as a family air loom for as long as it has if it had loose joints or poorly-set stones? In this series covering quality assurance for jewelry products, we’ll tell you what determines a quality piece and how to spot the imitators.

 

Inspection Methods

Jewelry items are special and require specific inspection methods due to their smaller size and detailed workmanship. Items of jewelry and jewelry stones should be inspected with the naked eye within a recommended range of 30 cm. Jewelry items should be lit under balanced daylight, with the aid of precision lighting and inspected from inner and outer sides during visual inspection.

Casting

Casting is an important point to verify during jewelry QC and is first on our list. There should be no noticeable defects or discoloration visible on metal components of the jewelry pieces. Examples of common defects related to casting are:

A stress crack in ring casting.

-          Fire scale/burn marks

-          Porous areas, recesses, dimples or impressions

-          Parting lines

-          Filled air bubbles

-          Stains, haze or dull film

-          Distortion of shape

-          Stress cracks

In addition, all lines and edges should be smooth and run along the same plane without any wavy or serrated irregularity. Quality casting for jewelry items shouldn’t have rough edges.

Soldering

All soldered parts must be securely joined and aligned to ensure durability. Soldering materials should be consistent in color with the metal joined. Soldering should be indistinguishable from the surrounding metal and areas around the soldered points should be even and smooth. Keep your eyes out for the following quality defects when conducting jewelry QC:

-          Excess soldering material on the joint

-          Pits or holes in the joint

-          Cracks in soldering

-          Distortion of the shank

-          Uneven fitting of parts and swing joints

-          Scratches , cracks and chips on inserts

A piece with an insecure joint on the left in contract with a piece on the right that has been properly at the joint. 

Glue Assembly

All glued parts should be securely joined and aligned. A securely glued joint is ensured by using the right type and amount of glue for the right kind of material. All glue should be completely dry before the jewelry item is packed and shipped. There shouldn’t be any visible or excess glue on either the front or backside of the item. Lastly, when natural, opaque gemstones and cultured pearls are set in precious metals, glue should always be used in conjunction with another setting method such as with pegs or prongs. It’s recommended that glue, epoxy resin or similar binding agents NOT be used for setting natural transparent gemstones such as topaz or amethyst due to easier visibility.

 

 

The jewelry piece on the left shows excess glue, while the item on the right is clean and free of any glue residue.


John Niggl is a Client Manager at InTouch Manufacturing Services, a QC firm that performs product inspections and factory audits in China for US and EU clients. John also writes for the QC-related blog, Quality Wars.

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