I have walked around the same streets so many times, and then seen a place that had been hidden to me. I now know the sites in a way that makes me think I could have made better use of the connections between place and snowball.

I have worked with this red all over the world - in Japan, California, France, Britain, Australia - a vein running round the earth. It has taught me about the flow, energy and life that connects one place with another.

I soon realised that what had happened on a small scale cannot necessarily be repeated on a larger scale. The stones were so big that the amount of heat required was prohibitively expensive and wasteful.

It takes between three and six hours to make each snowball, depending on snow quality. Wet snow is quick to work with but also quick to thaw, which can lead to a tense journey to the cold store.

Occasionally I have come across a last patch of snow on top of a mountain in late May or June. There's something very powerful about finding snow in summer.

People do not realise that many of my works are done in urban places. I was brought up on the edge of Leeds, five miles from the city centre-on one side were fields and on the other, the city.

Stones are checked every so often to see if any have split or at worst exploded. An explosion can leave debris in the elements so the firing has to be abandoned.

The first stone was just tried in the spirit of experimentation. The opening of the stone was far more interesting than the drawing that I had done on it.

The hardened mass of liquid stones had much stronger qualities than those which had simply torn. The skin remained a recognisable part of the molten stone.

The relationship between the public and the artist is complex and difficult to explain. There is a fine line between using this critical energy creatively and pandering to it.

The stones tear like flesh, rather than breaking. Although what happens is violent, it is a violence that is in stone. A tear is more unnerving than a break.

Three or four stones in one firing will all react differently. I try to achieve a balance between those that haven't progressed enough and those about to go too far.

Snow provokes responses that reach right back to childhood.

A snowball is simple, direct and familiar to most of us. I use this simplicity as a container for feelings and ideas that function on many levels.

Even in winter an isolated patch of snow has a special quality.

A stone is ingrained with geological and historical memories.

I enjoy working in a quiet and subversive way.

People also leave presence in a place even when they are no longer there.

Winter makes a bridge between one year and another and, in this case, one century and the next.

My art is an attempt to reach beyond the surface appearance. I want to see growth in wood, time in stone, nature in a city, and I do not mean its parks but a deeper understanding that a city is nature too-the ground upon which it is built, the stone with which it is made.