Cutlery
Ever wonder what makes cutlery so shiny?
Utensils are a tool that most of us use everyday, and while they are seemingly ordinary, the chemical processes that go into manufacturing them are quite interesting. Before the discovery of stainless steel, cutlery used to be made from gold or silver. These were the metals of choice because both Gold (Au) and Silver (Ag) are malleable making them easy to mold and more importantly, they are inert. Gold and Silver have high electrode potentials – the ability of an element to retain its electrons - and thus prevent any metallic taste from entering the food since they are less prone to oxidation. Silver became the more common choice for cutlery manufacturing (hence the name “silverware”) because it was cheaper than Gold.
While Silver was the cheaper option, cutlery was still very expensive and became a symbol of the upper class. It was not until the discovery of stainless steel that made cutlery affordable and widely available. Stainless steel is an Iron (Fe) alloy consisting of elements like Chromium (Cr), Nickel (Ni) and Molybdenum (Mb). When imbedded in steel, these elements provide corrosion resistance and prevent any stains that arise because of rusting (hence the name stainless steel). When the alloyed elements are exposed to the oxygen in the atmosphere, a metal oxide film forms and protects the steel from corrosion. Since stainless steel is more corrosion resistant, that prevents any metallic taste from entering food which makes it an excellent material for cutlery.
Modern-day cutlery is made by stamping stainless steel sheets into the desired shapes. Once the desired shape is obtained, the cutlery must be polished to give it that distinctive shine. One of the most common methods to achieve this is using a process called electro-polishing. In this process, the manufactured cutlery is lowered into vats of phosphoric acid and is hooked up to an external circuit. The stainless steel parts become the cathode (negatively charged terminal) and another piece of metal is designated the anode (positively charged terminal). Voltage is applied to the circuit and current runs to the part. The harsh conditions of the phosphoric acid, specifically the low pH, promote metallic atoms from the cutlery to dissolve in solution, becoming ions. Proprietary additives ensure that the metal atoms dissolve in an orderly fashion leaving a highly ordered, leveled surface. The flatness of the surface allows more light to bounce off the cutlery which gives the cutlery its shimmery appearance.
Nowadays, cutlery can be made from any materials such as plastics, ceramics and all kinds of metals. The different chemical processes used in each will be discussed in different contexts in future blog posts! Although numerous materials can be used, stainless steel prevails as the most prominent. While today’s silverware is still silver in colour, its composition is much different and improved thanks to chemistry.
