Glamorgan 241 for 8 (Hemphrey 60) trail Gloucestershire 463 (Higgins 103) by 222 runs
A quick-fire Ryan Higgins century steered Gloucestershire into a commanding position against Glamorgan at the end of the second day's play in Newport.
Higgins reached 103 as the visitors posted a first-innings total of 463 and Glamorgan, 241 for 8 and needing a further 73 runs to avoid the follow-on, suffered more trouble when their captain, Chris Cooke, injured his ankle while turning to take a second run. Cooke is unlikely to take any further part in this game.
Gloucestershire added 103 runs to their overnight score before they were all out, gaining maximum batting points. Higgins and Graeme van Burren shared a partnership of 96 for the seventh wicket, before van Burren was leg before to van der Gugten for 25.
George Drissell and David Payne went cheaply, but Higgins, taking advantage of dropped catches, went on to score a rapid century from only 89 balls, his second hundred for Gloucestershire in successive seasons.
Glamorgan's openers had an awkward 15 minutes to negotiate before lunch, but lost Nick Selman in the penultimate over before the interval, when he was lbw to Payne.
Marnus Labuschagne was then out to the second ball after lunch - Payne taking two wickets in three balls - but Charlie Hemphrey and David Lloyd avoided a complete collapse by adding 95 for the third wicket. During their partnership, a sight screen panel collapsed, but fortunately no one was injured.
Hemphrey completed his first fifty in Championship cricket but, after reaching 60, he was out lbw to Drissell's off-spin, the 20 year old having earlier deceived Lloyd to have him stumped for 37. Drissell bowled a testing line and was helped by the rough created by the Gloucestershire left arm seamers and also Graham Wagg, who bowled 21 overs in the visitors' first innings.
Jeremy Lawlor and Billy Root settled in, but both were undone by Matt Taylor, who had Lawlor leg before with one that kept low, while Root played on.
Wagg and Cooke had put on 36 before Cooke was hurt and helped from the field in clear discomfort.
Marchant de Lange came and went, and much depended on Wagg if Glamorgan were going to get any where near the score of 314 needed to avoid following on. Wagg lost Kieran Bull, who became Drissell's third victim, but was undefeated on 45 at the close.
Glamorgan coach Matthew Maynard said it was too early to fully assess Cooke's injury.
"We have to wait until the swelling goes down and hopefully we will be able to know more at the weekend after he's had the scan," Maynard said. "Meanwhile Tom Cullen, the second-team keeper will come into the team for the two remaining days, and David Lloyd will assume captaincy duties"