Bowls of soup make you think. In my experience no other dish can stimulate the brain in quite the same way. The other day I was lost in a soup-induced reverie when two things occurred to me, firstly that I had forgotten to take the spoon out of my mouth, and secondly that it had no taste at all – there was no taste of spoon.
Taste buds located on the upper surface of the tongue can distinguish between five basic tastes: bitter, salty, sour, sweet, and umami, although ‘fat’ is now becoming a candidate too. These are not the only components of the sensations associated with taste. Other important factors include smell, detected by the nose; texture, detected by mechanoreceptors; and temperature, detected by thermoreceptors. In contrast, the taste of inedible materials like spoons is often discussed in terms of their chemical reduction potential, in other words their susceptibility to being oxidized in the mouth. These potentials have been measured for most materials and confirm broad trends of taste, where metals like copper, iron, and aluminum taste strong. Well, that's an understatement! No one can forget the brain-curdling sensation of accidentally crunching the foil wrapped around a piece of chocolate. On the other hand, if you suck a piece of gold jewellery, you’ll find it is almost tasteless. I specify jewellery because not many people own gold spoons. They are incredibly expensive and thought to be rather gauche, so they are only found in banquets held by lavish dictators where their presence does nevertheless ensure good taste for the guests.
Before modern times, most people used wooden, bone, or ceramic spoons. This is because the only metals that were economically affordable were iron, brass, bronze, and pewter, all of which give an unpleasant flavor to food. Plastic spoons came into use in the 20th century but despite their inertness, they didn’t make it to the dinner table. To be born ‘with a silver spoon in your mouth’ was a sign of great fortune and plastic spoons could not compete. Besides which, polish and glitter are an important part of the senso-esthetic experience of eating: we eat with our eyes as well as our mouths. A polished spoon also says something else to an eager diner, it speaks of cleanliness in a way that no matt plastic surface can – witness the obsession with shiny kitchens and bathrooms. No, the world needed a new metal as inert as plastic and not as expensive as silver that would allow everyone to eat like royalty.
Silver- and chrome-plated spoons did make some inroads into this hierarchical state of culinary affairs but it was one metallurgist working in Sheffield, UK, who made the breakthrough, and in doing so revolutionized every cutlery drawer in the world.
The story goes like this. One day in 1913, Harry Brearley was given the job of investigating alloys to create improved gun barrels. He was working in one of Sheffield's metallurgy labs, adding different alloying elements to steel, casting test specimens and then testing them. His genius was not that he preserved and organized his specimens because he didn’t. He tested them and if they didn’t look promising he chucked them in the corner. His genius was that when a month later he walked through the lab and saw a bright gleam in that pile of rusting specimens, he didn’t ignore it and go to the pub, but instead he fished out the one specimen that had not rusted. How could this be, a steel that doesn’t rust? If anyone had even suggested this was possible by just adding chromium, they would have been denounced as mad, and yet here he was holding in his hand a miracle – stainless steel.
Of course we take it for granted now, and even at the time, French and German scientists were onto it, so maybe the ubiquity of stainless steel was inevitable. It is everywhere now, from shopping malls to kitchen sinks, from gleaming corporate art to the spaghetti profusion of corrosion resistant pipes in chemical plants. In less than 100 years it has become the metal with which we are the most intimately acquainted; after all we put it in our mouth almost every day. Sometimes it is the absence of something that is most significant. Next time you drink soup, marvel at the absence of the taste of the spoon and salute Harry Brearley.