Glamorgan 242 and 46 for 0 lead Sussex 203 (Hudson-Prentice 59, Harris 3-38, Swepson 3-52) by 85 runs
Glamorgan's bowlers fought their way back into this game, dismissing Sussex for 203 as the home side finished with a lead of 85 and 10 second-innings wickets standing
A first-innings lead of 39 could be crucial in a low-scoring contest. Australian leg spinner Mitch Swepson took the last two wickets in two balls to wrap things up, finishing with 3 for 52, while seamer James Harris returned figures of 3 for 38.
When he went for 59, the rest of the Sussex innings folded. Glamorgan openers Zain-ul-Hassan and Andrew Salter went about patiently increasing that lead, as the home side finished the day on 46 without loss.
The Australian Kookaburra ball is being used for this match, with Glamorgan's bowlers using it to good effect to stem the runs for long periods as well as taking regular wickets. Sussex scored at just over two runs an over as they struggled to evade the fielders with their few attacking shots, as the home bowlers maintained a stranglehold.
It was the 30th ball of the morning before Sussex added to their overnight score, by which time Timm van der Gugten had added his second wicket of the innings by bowling Tom Alsop for 27, while Jamie McIlroy dismissed Tom Clark lbw for 32.
Then it was the turn of Harris to get in on the act, getting the wicket of James Coles with his first ball and then adding that of Danial Ibrahim to leave Sussex struggling on 95 for 5.
Hudson-Prentice and Oli Carter were patient in their efforts to rebuild the innings before the wicketkeeper fell caught behind off the bowling of McIlroy. Nathan McAndrew was caught and bowled by fellow Australian Swepson.
Offspinner Jack Carson then provided valuable support in a partnership of 61 with Hudson-Prentice which edged their team ever closer to Glamorgan's first-innings total of 242. Carson was given a life when dropped by Billy Root off Zain, however, the end came suddenly as Glamorgan wrapped the innings up with three wickets in four balls.
First Hudson-Prentice's watchful innings was undone when he skied a short ball from Harris, then Carson fell lbw and Aristides Karvelas caught behind by Chris Cooke, both to Swepson who will be on a hat-trick ball when he next bowls.
Zain and Salter found getting runs equally difficult in the early stages of Glamorgan's second innings, before scoring a little more freely in the last few overs of the day. They will look to build a match-winning lead, while Sussex will take confidence from the way Glamorgan were able to keep taking wickets as the Kookaburra ball got older.