Perth - South Africa continued to bat Australia out of the first cricket test by extending the lead to 506 runs at lunch on the fourth day at the WACA on Sunday.
South Africa was 508-7 at the break with Vernon Philander and debutant Keshav Maharaj unbeaten on 63 and 19 respectively.
Overnight pair of Quinton de Kock (64) and Philander batted untroubled in a 116-run seventh wicket stand as the game gradually got away from the home side.
With the wicket suiting batsmen despite widening cracks, South Africa ground out the Australian attack after starting the day on 390-6.
De Kock, who was the mainstay in South Africa's first innings 242 with a brilliant 84, made a plucky 64 to again thwart Australia's hopes for early inroads to the tourists' lower order.
Australia came close to dismissing him twice in the first hour when he was adjudged out by the onfield umpire. But the lefthander successfully challenged the caught behind and the lbw on 28 and 47 respectively, much to the dismay of the hosts.
De Kock finally drove uppishly and was well caught by Adam Voges at cover off Mitchell Marsh (2-77). He hit two sixes and five fours off 100 balls in 2 1/2 hours.
Philander had batted for just under three hours, with a six and 10 fours off 132 balls.
This was after Dean Elgar (127) and Jean-Paul Duminy (141) on Saturday shared a 250-run third wicket stand to bat the Proteas to a match-controlling position.