Hairline crack

All I can say is it worked here. Whereas pollyfilla etc didn't.

Quite. And I'd guess most ceilings are going to be painted.

I have - when younger, papered ceilings. It hides the cracks.

Worst piece of advice ever.

You cannot paint on silicone

If you want a flexible crack filler use decorators caulk

With many cracks I've found their reappearance or not is unpredictable. I've not noticed the filler type make any difference, but I don't fill cracks day in day out.

Rarely I've used silicone, it works but can shrink on setting, and can't be filled a 2nd time or painted. Since it leaves a film either side of the crack that can also peel it's hardly ideal.

NT

I obviously dug out the old pollyfilla.

I doubt you could squeeze caulk into a hairline crack anyway.

Which is why professionals widen the crack and fill with flexible caulk; to reduce the percentage of movement.

In the next few days I shall be papering the hall ceiling. The stairs and the landing are fine and the paper can be matched. It is just that we had a leak which damaged the hall ceiling; followed by my eldest son ignoring my intructions to use the toilet in the small bathroom and clambering over the blockade I'd put in the big bathroom, then putting his foot through the ceiling where I had the boards up :(

I've just finished replacing half the hall ceiling and am waiting for the joint filler to dry. I'd actually taken extra down to take the opportunity to route ethernet and satellite cables through there and to improve the run of the shower waste.

SteveW

they do that to get paid.

I've not met any filler that doesn't go into a hairline crack, other than coarse sand based stuff.

NT

Captain Tollys Creeping Crack Cure is really for sealing "cracks" that are no more than break in non absorbant materials that still have capillary action.

Personally I follow the line of the crack with the point of a trowel, making the crack wider and a few mm deep. Mix up some ordinary powder filler, fairly stiff, spray the raked out crack with water to reduce the suction, apply filler to crack with a flexible spatula filling knife/blade, making sure the crack is fully filled. Leave very slightly proud, layer of filler on surrounding plaster translucent thin but not critical if there are some thicker lines from the edge of the knife. Wait 10 mins, until the filler is partially set, wet the flexible filling knife and smooth the the lot leaving just a residue around. Leave to dry fully wipe of residue with damp cloth.

If the crack was caused by known movement that can't be sorted out rather than just a random crack I'd be tempted to use decorators caulk. Normally reserve that for timber/wall gaps, though more recently have used powder filler as above and again fairly stiff for that and it's not cracked, yet...