What is it with Chrome?
As you reflect in your bath (as you do), do you ever wonder about why tapsare chrome – or ‘chrome effect’? And wastes? And traditional shower heads? Well if the conundrum has been eating away at your brain, let me put you out of your misery.
As long as there have been bathroom fittings, there has been the mirror-finish of chrome. Or to give it its proper name, Chromium. Because back in 1797 Nicolas Vauquelin had succeeded in isolating the pure metal from a mineral compound (lead chromate or ‘crocoite’ if you must know). But the Chinese had easily beaten him to the discovery because some 2000 years back they were chrome-coating the weapons of their Terracotta Army figures.
Chromium’s usefulness stems partly from the facts that:
- It is the hardest of all metals
- It takes a very high polish
- It has a high melting point
- It resists oxidation and hence is anti-rust
Now mined (as iron chromium dioxide or ‘chromite’) in South Africa and several other countries, back in the early 19th century the USA was mining it and smelting it in Baltimore and it was well placed to supply the fast-growing metal processing industries. Chrome plating of other metals and the production of stainless steel (which uses 11% or more of chromium) are the main applications, although the preservative that stops any wood in your bathroom from rotting may well also contain the metal.
Think back to your father or grandfather’s car and it was probably dripping with chrome-plated metal, electroplated onto the surface of many components and glinting in the sunlight. Your own car now has plastic trim instead. In the bathroom too, heavy plated taps were always a status symbol. And in the modern bathroom, the typical tap body is still made from a brass moulding, maybe with zinc moulded tap handles, all plated with chrome. (See this pair of traditional Tavistock taps from Plumbworld, for example).
Nowadays you are increasingly likely to see the words ‘chrome finish’ and you may think that you are being fobbed off with an inferior product.
This is not necessarily so. The fact is that the chromium plating process has environmental problems because it generates some known carcinogens, and alternative treatment processes like plasma nitriding are often preferred as a result.
There is an increasing preference for a more subtle finish that does not scream ‘look at me’ and which also doesn’t show the dirt so easily – so you will be offered stainless steel and nickel fitments, although still more often in the kitchen than in the bathroom. Upmarket Bristan sink taps are a good stainless steel example.
And of course there has been the rise and rise of plastics and alloys, and for reasons of cost and lightness this is not surprising. The question is then begged, how do you create a convincing chrome effect on fittings like tap handles, shower heads and sink wastes? The usual method is known as Thermal Vacuum Metallisation (but of course you knew that). The process goes like this:
- Moulded components are sprayed with a base lacquer coat
- They go through a stoving process
- In a vacuum chamber, a charge is passed through tungsten filaments containing pure aluminium
- The aluminium vaporises and coats the rotating components, giving them a mirror-chrome finish
- A top lacquer goes on to protect the finish – this may be made especially resistant to perfumes, alcohols etc.
I should also say that the top coat can be made to create coloured metallic finishes such as gold – Footballers’ Wives anyone?