Planned strikes at the National Museum Wales were suspended last weekend following talks with bosses.
Workers in the PCS union are in dispute over the withdrawal of weekend working allowances.
The change would involve slashing the income of many staff by up to £3,000 a year.
Bosses have offered workers a new deal which PCS says is inferior.
But they have agreed to consult members on whether to ballot to accept the deal after bosses threatened to remove the offer and replace it with an inferior one.
Giving in to this is a mistake. Workers have shown they are up for a fight, walking out in a series of strikes since July. They are still taking part in action short of strike until 30 September.