Play didn’t get under way until 2.30pm because of a wet outfield then drizzle and bad light returned after tea. Only 30 overs had been bowled when umpires Ian Gould and Mark Newell called off play at 6pm.
Salt had been put down at gully by Dan Lawrence in the 18th over on 32 and looked like making south group leaders Essex pay as he reached his third half-century of the season.
But Porter, who had already removed Tom Haines for 14, picked up a second wicket after switching ends when Salt was well taken low down at second slip by Simon Harmer in the 24th over after facing 82 balls and hitting 11 fours.
It could have been an even more productive session for Porter but umpire Newell turned down appeals for a catch at the wicket when neither Harry Finch nor Tom Clark had got off the mark.
In overcast, muggy conditions there was no surprise when Essex chose to bowl first but there was surprisingly little movement through the air for the Essex pace bowlers as Salt and Haines added 38 in 13.3 overs with few problems.
Haines had looked solid in making 14, including two boundaries in an over when Matt Quinn went round the wicket to the left-hander, but he wasted an hour of careful reconnaissance by driving expansively at a ball he could easily have ignored and Harmer held a sharp chance at waist height.
Porter had just switched to bowling down the slope after four unproductive overs from the sea end during which Salt twice drove him down the ground for four.
Salt was quick to punish any bowler who pitched short, pulling Matt Quinn to the boundary in the 21st over after Quinn had replaced Aaron Beard at the sea end.
Salt showcased impeccable timing when he clipped Quinn through mid-wicket to bring up his half-century with his tenth four and drilled the next ball back past the bowler for another handsome boundary before Porter struck back.
Harmer bowled three overs of probing off spin before tea with Finch driving him through the offside for a boundary as he reached 20 not out. Left-hander Clark, who made his maiden first-class fifty in last week’s defeat by Kent, is yet to get off the mark.