Oh jesus what fooking kind of s**t is this stuff.Used this stuff onto heat resistant plasterboard from victas. These boards were fixed onto MF studwork where a gas fire was incorporated.Boards were pva'd as insttructed,joints caulked with victas plaster and scrimmed with 'heat resistant scrim'.I then applied this 'toffee like plaster' while boards were tacky,trowled off as smooth as possible(which was pretty smooth).I then left it alone for 3-4 hours,came back to it and noticed a load of hairline cracks appearing.I trowled the surface again and cracks seemed to disperse so i thought all was ok.All looked ok upon my departure home that evening.When i arrived in yesterday morning there were hairline cracks all over it and what looks like expansion cracks where the joints are in the board.It looks like scrim was never used at all. Has anyone ever come across this sort of problem and have any ideas as to how to rectify.I know there is a victas filler which can be purchased so is this my only option.Area size is about 6sqm2