Flower blossoms on return
Andy Flower's fourth Liverpool Victoria County Championship century of the season led Essex to 265 for four in reply to Gloucestershire's 394 in the Division Two match at Bristol.
The Zimbabwean, who survived a difficult chance to wicket-keeper Steve Adshead when on 62, closed the second day's play on an unbeaten 114, having hit 12 fours and a six in his 182-ball innings.
Opening batsman Mark Pettini also contributed 59 and his third-wicket partnership of 111 with Flower - back in the side after a back injury - revived the innings after Varun Chopra and Ravinder Bopara had departed cheaply.
Left-arm spinner Ian Fisher was the pick of the seven bowlers used by Gloucestershire, finishing with 2-86 from 22 overs.
Gloucestershire started the day on 355 for eight and Fisher and Jon Lewis extended their partnership to 65 runs and by a further 11 overs before Essex made the breakthrough.
It came when James Middlebrook had Lewis stumped by James Foster for 38, after the Gloucestershire captain had stepped down the pitch and attempted to drive the off-spinner over the infield.
Gloucestershire's hopes of reaching maximum batting points ended five overs later when Fisher, on 45, edged Andy Bichel to Bopara at second slip.
Chopra marked his first-class debut for Essex by scoring a century and a half-century against Gloucestershire at Chelmsford in May.
But the England Under-19 captain had only made seven this time when he attempted to cut a delivery from Lewis and edged a catch to Adshead.
Gloucestershire had more to celebrate from the fourth ball after lunch when Steve Kirby drew Bopara forward and induced another edge for Adshead to take.
However, that was the home side's last success for 31 overs as Pettini and Flower revived the innings.
Pettini progressed to a sedate 133-ball half-century, with eight boundaries, while Flower batted with greater freedom to bring up his 50 from 76 deliveries.
Gloucestershire were convinced Flower had been caught behind off Gidman on 49, but umpire Ian Gould rejected the appeal and Flower responded by cutting the next delivery to the cover boundary.
Pettini's 152-ball innings ended in the 46th over when he mistimed a pull at Fisher and Matt Windows took a straightforward catch at midwicket.
Flower then enjoyed a reprieve on 62 when Adshead spilled a low chance off Gidman in the last over before tea and with the total on 159.
Essex captain Ronnie Irani gave Flower gritty support in a fourth-wicket stand of 44 in 22 overs, which ended when Irani was caught at silly mid-off by Kadeer Ali off Fisher for 12.
Grant Flower joined his brother in the middle and the pair batted out the final 17 overs of the day to raise Essex's hopes of establishing a first-innings lead.
Flower reached his 168-ball century with a square-driven boundary off Ian Harvey off the final ball of the 79th over.
His brother ended the day on 28, having hit a straight six off Fisher and another one over midwicket off Chris Taylor.
