Day 3: As it happened
Adam Voges concedes Australia are treading a fine line in their handling of the ball as they strive to use the dark arts of reverse swing in their push for the No.1 Test ranking.
The Australians, who are on the verge of breaking New Zealand in the second Test, were again warned by umpires for throwing the ball in on the bounce from the field in an attempt to scuff up the ball and make it more conducive to "go Irish". 
While the outfield at Hagley Oval is lush, there are several abrasive patches on the neighbouring wickets that a fielder can aim.
Reverse swing was used with great effect in the first Test and was a major weapon for Australia as a fired-up James Pattinson landed several telling blows in the final session on Monday.
Pattinson was given a "rocket" from the coaches for his no-ball that reprieved Brendon McCullum on day one and responded by taking three top-order wickets.
Such was the movement Australia's bowlers generated, a bemused McCullum took the unusual step of picking up the ball to inspect its condition. He could have been given out handling the ball had the Australians appealed. The Black Caps captain had earlier seen his attack struggle to move the ball off the straight for five sessions.
"He was probably having a look to see what it looked like, basically," Voges said.
"We've probably got it going more than what they have. It can be to do with the conditions as well, the wicket is probably drying out a bit more abrasive so the ball is scuffing up a bit more but I'm sure he was just having a look to see what was happening."
The Australians take great pride in the way they look after the ball. Once they identify it will not swing conventionally they work to get it reversing by polishing one side so it is considerably smoother than the other. The difference can be accentuated if one side is significantly worn.
Ball tampering is considered one of cricket's ugliest offences.
"There's a line. I'm sure most fielding teams will get as close to the line as they can without overstepping it," Voges said.
"That's the umpires' job - to tell us when we're getting close. That's what happened today and we kept it up pretty well after that."
Voges put the extra movement Australia's bowlers were able to extract down to their higher speed.
"That maybe exaggerates reverse swing a bit more and our guys seem to be able to go a little bit both ways, which maybe exaggerates it a bit more," Voges said.
Pattinson was arguably Australia's best reverse swing merchant. The firebrand quick played the role of pantomime villain as he repaid the debt he owed his team from his no-ball on day one, which gifted McCullum a life.
He was jeered by the partisan crowd after an emphatic appeal for a return catch. Replays showed the ball had hit the ground and deflected off McCullum's leg before ballooning to the bowler. Pattinson even had the nerve to fire choice words at the retiring star, who made 25 in his final innings.
Pattinson was given a fierce spray by the Australian coaching on Saturday night for overstepping to McCullum, who then made the fastest century in Test history.
"Yeah the coach didn't miss him after play on day one, and that's probably putting it nicely," Voges said.
"Look, he got a rocket and he's come out and responded the way he did. So he probably didn't disagree with anything the coach said after play that night but full credit to Patto the way he's bounced back and he was excellent today."
New Zealand finished day three on 4-121, a deficit of 14, needing a herculean innings from Kane Williamson if they are to give Australia any meaningful final-innings chase.
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