Paceman Pedro Collins took the key wicket of South African captain Graeme Smith before the close as the West Indies scented victory on the fourth day of the first Test in Georgetown on Sunday.
South Africa, who followed on 355 runs behind, reached 85 for two in their second innings when bad light ended play three overs early.
Jacques Rudolph was 19 not out with Jacques Kallis on one.
South Africa were dismissed for 188 in their first innings after the West Indies declared their first innings closed on 543 for five declared.
Smith was bowled off his inside edge for 34 by a swinging delivery from Collins 16 overs before the enforced close, ending his careful innings after 142 balls.
The three-man West Indies' pace attack shared nine wickets between them in South Africa's first innings.
Collins took three for 39, Daren Powell claimed three for 61, and Reon King picked up three for 48.
But Collins felt the slow and low Bourda Oval pitch did fast bowlers few favours.
"I wouldn't want to bowl here too often, it's very slow and you don't get much sideways movement," he said.
South Africa resumed their first innings on 130 for six, and they slipped to 158 for seven in the 14th over of the day's play when Nicky Boje was bowled off his pads by a straightening delivery from King.
Boje batted solidly for his 34 and his dismissal ended a steadying stand of 63 scored with Mark Boucher.
South Africa's last genuine hope of reaching the follow on target disappeared when Boucher drove at a wide delivery from Collins and was caught at first slip by Shivnarine Chanderpaul.
Boucher scored a defiant 41 off 158 balls with five fours.
The only low point of South Africa's first innings for the West Indies was the 31 no-balls their attack bowled.
AB de Villiers and Smith opened South Africa's second innings three overs before lunch.
They batted cautiously until De Villiers dragged the sixth delivery after tea, bowled by King, on to his stumps to be bowled for 20.
South Africa might have been 62 for two, but Devon Smith at slip failed to hold a sharp chance after Rudolph, on two, edged a ball from Deonarine.
Smith's dismissal followed, and Rudolph was dropped again on 14 when left-arm spinner Ryan Hinds spilled a return catch.
Scorecard:
West Indies 1st innings 543 for 5 decl (W. Hinds 213, S. Chanderpaul 203 not out)
South Africa 1st innings (overnight: 130-6)
G Smith c Browne b Collins 2
A Villiers c Browne b King 41
J Rudolph c R Hinds b Powell 0
J Kallis b Powell 0
H Gibbs lbw b Collins 5
M Boucher c Chanderpaul b Collins 41
A Hall c Collins b King 2
N Boje b King 34
M Ntini lbw b Powell 8
C Langeveldt c R Hinds b Deonarine 10
A Nel not out 6
Extras (lb-6 nb-31 w-2) 39
Total (all out, 66.5 overs) 188
Fall of wickets: 1-15, 2-16, 3-16, 4-30, 5-71, 6-95, 7-158, 8-169, 9-172, 10-188.
Bowling: Collins 18-5-39- 3 (nb-13), Powell 18-2-61- 3 (nb-5 w-2), King 16-2-48-3 (nb-11), R Hinds 13-5-29-0, Deonarine 1.5-0-5-1
South Africa 2nd innings:
A Villiers b King 20
G Smith b Collins 34
J Rudolph not out 19
J Kallis not out 1
Extras (b-5 lb-1 nb-5) 11
Total (for 2 wickets, 63 overs) 85
Fall of wickets: 1-46, 2-68.
Did not bat: H Gibbs, M Boucher, A Hall, N Boje, M Ntini, C Langeveldt, A Nel
Bowling: Collins 9-6-12-1 (nb-1), Powell 12-7-15-0, King 8-0-18-1 (nb-4), W Hinds 8-4-4-0, R Hinds 13-6-13-0, Deonarine 12-5-17-0, Chanderpaul 1-1-0-0
