Mr Stewart was recently awarded the 2012 Prime Minister's science teacher prize. Reasons included hiking chemistry class numbers at the school by 44 per cent at NCEA level two and more than 100 per cent at level three, from 30 students to more than 70.
He came to teaching via an unusual pathway, working as a stockbroker in London, training as a chiropractor and a few other jobs along the way.
The youthful 48-year-old liked science at school but had no burning desire to teach.
That changed when he had his own children, now aged 8 and 9.
Having children changes how you look at teaching, he says. "You care more about things."
The changing colours of the flame have a purpose beyond fun, he says, helping children to understand the different properties in chemistry.
Teaching is never a grind and sometimes the rewards are great, such as when former students get in touch years later, like one now studying for a PhD in organic chemistry at Yale University in America.
"You remember [them] saying 'I think I'm going to struggle in that subject'."
