Sussex were on top in the opening overs of the match with Ollie Robinson and Harry Crocombe getting the ball to move late, but Glamorgan game back into it thanks to Carlson’s hundred and David Lloyd’s 84.
Robinson had Nick Selman trapped lbw with the fourth ball of the match and had Andy Balbirnie dismissed the same way in the seventh over of the Glamorgan innings.
When Crocombe got another lbw, this time Billy Root, Glamorgan were 23 for three and in serious danger of collapsing.
Lloyd’s attacking intent and Carlson’s more measured accumulation blunted the Sussex attack, with both particularly brutal to the bowling of George Garton who went for 30 runs from just four overs.
It was Crocombe who ended Lloyd’s fine knock of 84 with a ball that bounced and moved away to give Garton a sharp catch at second slip to end a stand of 110 with Carlson.
Carlson remained unflustered as partners fell around him with Glamorgan losing three wickets for 46 runs when Crocombe and Robinson were reintroduced into the attack.
Carlson was lucky to survive on 91 when Tom Clark’s first ball was edged to Garton at first slip who failed to take the chance diving to his right. Had the chance been taken it would have been a wicket with Clark’s first ball in first class cricket. He made the most of this good fortune, registering his fifth first class hundred from 152 balls.
An 87 run stand between Carlson and Dan Douthwaite took Glamorgan to 266 for six. Douthwaite was just starting to open his shoulders and look to score quickly when he mistimed a drive off Stuart Meaker for 36.
Three quick wickets from Jack Carson rounded off the Glamorgan innings with Carlson unbeaten on 127.
While Carlson and Lloyd had done well the Sussex opening pair put Glamorgan’s efforts into context. Thomason made 52 and Haines 43 with none of the Glamorgan’s bowlers getting the same movement with the new ball that Robinson and Crocombe had managed.
Robinson said at the end of play: “It was good to get three early wickets. We let it slip a little bit in the second hour but I thought the rest of the day we were on top. We pulled it back a little bit after lunch and Jack Carson finished off their innings with three quick wickets which was very handy."
On bowling first, Robinson added: “We just thought it had live grass on it and the best time to bowl would be the first day. Kiran Carlson played very well and stopped us from bowling them out for 200. Overall we have had a good day. The lads batted well tonight and we finished well.”
Praising Haines and Thomason, Robinson said: "They’ve worked really hard this winter in the tent at Hove in pre-season. They have both made big strides and looked really solid at the moment. So that is good to see, and good to see that we have that solidarity at the top of the order. It sets us up well for the rest of tomorrow and hopefully we can get a big lead."