Compared to bonding automotive or aircraft components, you would think a jewelry bonding application would be a walk in the park. Surprisingly, this isn’t always the case. Think about the wear and tear a ring would have. In and out of hot soapy washing-up water or a set of earrings getting a regular shampooing. Bond areas are tiny. And the wearer exposes it to water, soap, hand cream, cleaning fluid, detergent etc. It is really important the jewelry maker uses the right adhesive for the job. Otherwise, they will have dissatisfied customers, returns, and repairs to deal with.
You will find precious gemstones such as rubies, diamonds, sapphires, etc. are held in place firmly by claw settings formed in gold. These last hundreds of years with minimal upkeep. This manufacturing method is highly skilled and carried out by expert jewelers. Manufacturers of high-volume costume jewelry want a quick, low-cost solution. Often using basic adhesives such as solvent-based craft glue or hotmelt adhesive.
Cyanoacrylate adhesives also give a fast and accurate method of attaching crystals or rhinestones. These types of adhesives will not stand the test of time like the claw setting on a gold ring. Possibly the lifespan is long enough for the wearer to lose interest in the jewelry item and move on to the next fashionable piece. However, some of these semi-precious crystal jewelry items can be several hundred dollars. The loss of several stones or the discolouration of the adhesive attaching them is very disappointing. Larger stones or decorations may fair a bit better as they would have a larger bonding area and a smaller ratio of exposed glue line.
Yes, epoxy adhesives have much better environmental resistance and can withstand hot soapy water without degradation. Permabond offers clear/colourless two-part ET500 and single-part heat cure epoxy ES560, which for jewelry applications. These are ideal for use in thin glue lines for bonding glass, stone, most plastics, and metals. It should be noted that they are probably not the best choice of product aesthetically if you need to produce a thick dome coating.
UV adhesives offer the best aesthetic appearance, excellent environmental resistance, and a very quick manufacturing process. For clear crystal bonding, a regular UV-curable clear adhesive such as Permabond UV670 is ideal. However, often rhinestone crystals have a foil backing, in which case the UV light may not penetrate for adequate curing. Dual cure Permabond UV7141 offers a sophisticated bonding solution for bonding gems to metal where shadow areas could be a problem. The product can be cured immediately by flashing with UV light (which will cure around the edges, hold the crystal in place). Then the adhesive underneath the gem will cure anaerobically (the surface of the metal and the absence of oxygen will cause the adhesive to cure).
Equipment for curing UV adhesive can be very expensive – particularly for production line conveyors and high-intensity lamps, shielding, etc. But there are some really easy and low-cost “home” alternatives. We have seen customers using sunbeds for curing adhesive for window bevels. Of course, jewelry is tiny by comparison. But a nail polish curing lamp is the ideal size for small jewelry items. These are on eBay for less than $50.
For more help and advice about adhesive selection, please contact Permabond.