The material, which he first worked with 27 years ago, is one he relies on for many of his sculptures.
A selection of his works is on display at Timaru’s Saffron Gallery of Art.
The exhibition includes works made using aluminium extrusions, a labour-intensive way to create sculptures without using ‘‘big technologies’’, he said.
‘‘It’s a simple, straightforward way of creating.’’
Mr Armstrong first exhibited 45 years ago and has used aluminium since 1989.
‘‘I’ve always painted on canvas, board or paper. I still do that all the time but I got into interesting movements in the 1970s.’’
‘‘Even when I was at art school in 1974 [I started exploring] ways of getting beyond the rectangle of conventional painting, so I cut holes in paintings,’’ he said.
He bought a sewing machine to use in his work.
‘‘Then in 1986 I started using plywood and still do a lot to make sculptures.’’
His works were ‘‘almost always painted’’ and many were designed to hang on a wall.
They were often big creations.
The Runner, for example, made from aluminium, stands about 2m high.
It started as an abstract concept, Mr Armstrong said.
‘‘Then [I] just kind of kept opening up other possibilities and it slowly transformed itself into the figure, which I thought was a very interesting concept.’’
The Runner, and other works are now on display at Saffron Gallery of Art, where Mr Armstrong has been named artist of the month.