The great joy of drawing is that you become better at it the more you practice. As one gets older, one’s performance at most things deteriorates. But with drawing, I find that it actually improves.

I still have the sketch I made of the old library at St. John’s, when I was an undergraduate between 1952 and 1955, but it is rather quick and slapdash compared with the drawing I made in September 2009. The recent drawing is informed by practice over these last 10 years at the Prince of Wales drawing School; by drawing Old Masters in the National Gallery; by life drawing at the Royal Academy; even by sitting in the street drawing scenes of London. These are not quick sketches but detailed drawings, which can take 12 hours over several days to complete. For me, drawing is totally absorbing and satisfying.

It is pleasing to share one’s work with other people, but I do not like to sell my drawings, because it involves cutting them from the sketchbook — and I feel the loss of something which I cannot replace. But there’s another way: printing a drawing from a metal sheet, which allows one to make several impressions to share with others.

A scratch in the metal will hold ink, and gives rise to a process called drypoint — the method much favoured by Rembrandt. Alternatively, artists can use a hand-held chisel, called a burin, to gouge a line in copper or zinc. This is much deeper than a scratch and is called engraving. Finally there’s a third method, where the metal plate is covered with a protective coating into which the mirror image of the original drawing is copied. The drawing removes the coating so that when the plate is immersed in acid the drawn lines are eaten away. This process is called etching — and it’s a technique I’ve come to love.

To make an etching I first degrease a copper plate, paint the reverse side and file the edges. The plate is then heated and a ‘ground’ produced from a mixture of bitumen and rosin, which is applied evenly to the surface. I place my original drawing — on this occasion, of St John’s library — at right angles to a mirror and then redraw on a piece of paper, touching the copper, the mirror image of the original, so that when it is printed the image comes out the right way round.

This is more difficult than it sounds. For example, I have to remind myself where the sun is coming from and then reverse it so as to get the shadows the right way round in the final etching. It takes a whole day to produce the mirror image. When the plate is ready, I place it in a strong solution of ferric chloride, which etches the exposed metal. By controlling the bite of the acid, I am able to vary the strength of the image to create distance or nearness.

Further work is often needed to achieve the right tone. Aquatint — a rosin dust — is applied in a cupboard, and then melted onto the plate. Whites are protected with a varnish and then the plate goes back in the acid for 10 seconds. The next area of tone is then protected and the plate exposed to the acid for 20 seconds, in a process which is repeated until all the tones are accounted for. Deep blacks will take several minutes of exposure — and the whole process can take a whole day.

Once the copper is cleaned and ready for printing, it is warmed on a hot plate and coated with an oil-based printing ink. After cooling, the excess ink is removed with cotton scrim, and highlights can be created using chalk or a cotton bud. The inked plate is then placed on a flat bed press and dampened paper placed over it, which I protect with tissue and then cover with two or three felt blankets. The press is like an old-fashioned mangle: a roller passes over the blankets to apply sufficient pressure to transfer the image. Working flat out, I can produce a single impression in just under an hour — which more than justifies the limited number of prints which artists produce.

We have a fine tradition of etching and engraving in the UK, from the days of Hollar’s early maps of 17th Century London to Hogarth in the 18th Century with Gin Lane and the famous series of The Idle and the Industrious Apprentice. William Blake mastered the art of etching, and both Gilray and Cruickshank used it to make venomous cartoons of political figures at the time of the Napoleonic Wars.

The advent of photography reduced the demand for etchings to illustrate books, but at the end of the 19th century there was a renaissance with the work of DY Cameron, James McBey, and Sir Muirhead Bone, who produced a marvellous etching of the Canterbury Quadrangle in which all the figures of the dons are easily recognisable.

Most recently, artists like David Hockney, Lucian Freud and Norman Ackroyd have produced excellent work, which is contributing to a revival in the interest in etching as an original art form. In my own way, I hope I’m adding to the tradition.

An exhibition of John Owen’s work, called Oxford Etched on Copper, is on display at Blackwell’s in Oxford from June 1st to June 30th. All etchings © John Owen and photographs by permission of Rio Tinto plc.