A critical part of the glass caster's art is "annealing", slowly bringing down the temperature of the kiln so the glass cools from liquid at a steady and even rate without cracking.
Talking to glassmaker Ann Robinson in her Glendene studio in an industrial area on the banks of the Whau River, the opposite process seems to be going on - a slow warming up as she tries to talk about anything but her work.
"I find it really difficult being interviewed because I haven't got a hell of a lot to say," she says, after articulating clearly the thinking that drives her to make increasingly larger and more challenging objects.
"It's the exploration of a material, where it is at and it probably comes from my heart at some point but it's not hugely rationalised.
"It's more that you think about it as you are doing it and wonder what you are up to and what it means and why you might have chosen that.
"It's sort of an internal dialogue that's going on, but I don't think for a second that anyone else would be interested in that dialogue, can't imagine it, so I am just being true to my own sense of how I think this material could be expressed and the sorts of things I want to do with it."
She remembers a glassblower who attended a workshop she ran in the United States, and cast a concrete block in bright blue cobalt glass as his way to get to grips with the process.
"It was fantastic, a great thing to have done. All the elements were there that should be there: curiosity, an exploration, a complete lack of desire to manipulate people into seeing it as beautiful, just an interest in his own exploration and being perfectly happy to cast a cinder block."
Robinson says the castings get more difficult as she tackles larger sizes. "Every time you take a step up, you get into areas where things go wrong and losses can be quite expensive."
On a work table is an 80kg casting of a bromeliad flower that cracked in the kiln.
"I have tried to do that piece maybe four times now. It has got a problem but I am working it out and I will get it right," she says, describing the dogged process of exploration and learning that has put her technically as well as aesthetically at the front of her field.
The works for the new show at FHE Galleries are all large, a sign of Robinson pushing the limits of her new workspace.
"The show is informed by the fact I wanted to feel strong and express the thickness of glass and the massiveness of it. It's always a gut feeling that you want it to be like this and something comes from the solar plexus."
Forms are new and old. "The vessels just emerge as I have a need, but how many different sorts of bowls do you need to design?"
The wax mould for a wide, flat bowl, cut in half and stuck back together in a different way, becomes a new shape and new line of exploration. Plant and insect forms make their way into the pieces, as Robinson processes the past 20 years of living in the Waitakere Ranges.
The show's title, Divaricate, refers to the muelenbekia plant common to the ranges, the stalk making a 90-degree angle at every junction.
She has built the pattern into the surface of a bowl. It's one choice, then another, until there is no way back. Another recent bowl has a huge centipede crawling up the side.
"I've heard one got washed out of a bank at Te Henga after rain that was as big as a rake.
"It's a fascination and a terror. Centipedes are beautiful in the way they move and I can never capture that movement, so it's always an inferior replica of what the real thing is, but I am interested in what might be coming out of your subconscious mind.
"The centipede is what is under the surface, what is under the leaf mould of our minds. It's being involved in conservation in the Waitakeres and living in the forest; the things that are underneath and the things we fear in our personal lives and places we are scared to go to but looking at that fear is really important. I have a terrifying thought of putting my hand into leaf mould and having a centipede wind its way round my finger. I am scared of that, but here it is, it's part of the world, the not so pretty part, and I wonder would people accept that on this very pretty glass?
"Also I found it wonderful, the process, the fossil centipede. I made a clay centipede and cast it in white glass so it was the negative you saw, a fossil, so it reinforces back to things I love, history and evolution and the knowledge that creatures we know now have been massive in the past, and this could have been one."
She says her work is improving as her technical knowledge increases.
"I don't know what I would do if I stopped doing it. There is still a lot I want to do. I can remember standing on my doorstep in Parnell in a slightly depressed mood looking out over the road and thinking I have got to find something to do between now and death to entertain myself. And I thought glassblowing might be quite an exciting thing to do and decided to do that.
"Because I think that's what we are doing. We are filling in time between now and dying. So you've got to find something as interesting as you can find, and something you love doing."
* Born Auckland 1944. Diploma of Fine Arts, Elam, 1980.
* Honours include Lifetime Achievement Award, American Glass Art Society, 2006; Arts Laureate of NZ, 2004; Officer of the NZ Order of Merit, 2001.
* Robinson's work is held at Auckland Museum; Corning Museum of Glass, Corning, New York; Robert McDougall Gallery, Christchurch; National Gallery of Victoria; Te Papa; Victoria & Albert Museum, London.
What: Divaricate, glass works by by Ann Robinson
Where and when: FHE Galleries, 2 Kitchener St, to December 22