By using 18% nickel silver eye wire all Randolph Engineering sunglasses frames will not rust nor deteriorate, and the solder joints are extremely strong. In addition, Randolph uses their own solder flux for the joints as well.
[caption id="attachment_1882" align="alignright" width="300"] An Example Of Rosin core electrical solder[/caption] Solder flux is used for joining two metal parts together by heating the two parts, placing them next to each other and applying the solder flux to the parts. This joins the two parts together in order to complete the structure of the frame itself. In the image above you see a jig at Randolph Engineering that holds the parts of a pair of aviator sunglasses in place making sure they are properly positioned so that they can then be soldered together. Randolph Engineering not only uses solder flux they make themselves, but in addition use filler material made of 56% silver to give added strength to the joint and the frame itself. The definition for solder flux is as follows:
Solder flux is a type of metallurgy component used when soldering two metals together. The flux is an inert substance that prevents the formation of metal oxides at extreme temperatures.
Why Is Flux Needed?
Solder doesn't just freeze a joint together, it forms a metallurgical bond by dissolving and chemically reacting with the base material. The problem is that almost every metal will oxidize in air and forms an oxidized layer that prevents solder from becoming wet and bonding the parts together. Oxidation occurs quickly at high temperatures so no matter how clean the metal parts are to begin with you still need flux to prevent new oxidation to occur while soldering. The real choice when deciding on a flux is how aggressive it should be. Today flux is classified by how active it is, the material and halide presence.
Types Of Flux
Flux materials are Rosin, Resin, Organic and Inorganic. Most R and RMA fluxes fall under the low activity classification, while RA are considered moderate activity and water soluble as high activity. The two families of flux are resin based and acid based. Steel, Stainless Steel, Bright Steel, Iron usually solder better with Acid based flux, while Brass, Copper and Gold usually solder with either and it is dependent on the sensitivity of the components. Acid delivers the best results for soldering metals.
So How Important Is All This?
In material supplied by Randolph Engineering they state "We even make our own solder flux. As a result, our frames provide unequaled strength and solder joint integrity." In addition they use a 56% silver filler for the joints to provide extra strength. In fact, Randolph Engineering is so confident in their solder joints that they twist test every 50th pair in order to make sure the joints will not separate under any conditions. This is known as "The Randolph Engineering Twist Test".