A once-in-a-lifetime opportunity for collectors to own a precious piece of New Zealand art.

Bill Hammond's Melting Moments I goes under the hammer tonight for the first time- and it's expected to get about $2.5 million. 

It was painted during Hammond's three-year green and gold period.

Webb's Director of Art Charles Ninow says a lot of interest is expected tonight.

"These works are really sought after- there are hardly any of them, even though they are so iconic. Most people haven't even seen one in the flesh before, I've only seen a handful. It's a very, very exciting painting."

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