Special paint for skimmed Plasterboard cracks on ceiling

[MortarThePoint]

The vast majority of rooms have gone fine and are crack free, but the two largest rooms downstairs have quite a few hairline cracks at board edges. All edges were definitely scrim taped (Gyproc FibaTape Xtreme). The rooms are 6.4x4 and 10x4.6 and each plastered with Thistle MultiFinish in a single hit. The larger room was 15mm TE MR boards primed with Thistle BondIt. The other was 15mm SE WallBoard. It was a bit warm inside for this time of year 'on site', but something like 17C. Boards were attached to Gyplyner system (400c/c with brackets at 900c/c max.) and screwed at 200mm c/c or 150mm c/c at board edges.

 

I don't think the cracks appeared in the first couple of days, but can't be certain. The door is sometimes left open as work is done letting in cold air, but the room temperature has pretty much stayed above 15C.

 

I know about EasiFill/Paper Joint Tape/ EasiFill feathered in and sanded approach, but that would leave a slight hump and I made a huge effort to get the MF and plasterboard super flat. Has anyone tried the Crack Free paints? Two come to mind (linked below) but I'm worried that they are too good to be true. First hand experience would be very helpful. @nod have you encountered them or are they snake oil? The cracks are very fine.

 

PolyCell Crack Free Ceiling Paint

 

Zinsser Ceiling Pro 5-in-1

 

Some impressive pictures amongst the pictures of leaking tins.

Edited February 27 by MortarThePoint

[Kelvin]

Good timing. I have the same problem. I’ve tried the paper tape and redo and it cracked again. I’ve also tried caulk and it fixed one of them. 

[MortarThePoint]

1 hour ago, Kelvin said:

I’ve tried the paper tape and redo

Was that a complete reskim then? If so did you put MultiFinish between the original skim and the paper jointing tape?

[Kelvin]

New plaster over plasterboard. 
 

I scored the crack, smoothed filler over it

filling it in, then paper tape then another coat then sanded back. That crack came back albeit it’s barely visible. The other one I used a caulk type joint filler then finishing filler and sanded back. It’s been fine for a month or so. I have a long straight hairline crack in the ceiling that I think is because the plasterboard trapped something underneath it so it’s not flat. The paint stuff you posted might do a good job fixing that.