Oil based Primer won't dry when painted over PU sealer

[rcx132]

I've used PU sealer in a small under stairs toilet as the original caulk just shrank after a few years, cracked and looked terrible. I removed the caulk, sanded everything, applied the PU sealer. The sealer claims to be over paintable but any oil based primer I apply to it just never cures, not even after a week. I thought maybe the PU sealer needs more time to cure so I wiped off the primer, and gave it more time. But problem persists. I've re-read the PU sealer instructions, they say nothing about what sort of paint can be applied over it, just that it can.

I've previously used the sealer on car projects and overpainted it with epoxy primer, which had no problem curing then.

 

[JOEPRO]

There are decorators mate type products for this purpose which are truly over paintable.

That stuff above looks more like it is a rubber type sealant product.

 

[rcx132]

There are decorators mate type products for this purpose which are truly over paintable.

That stuff above looks more like it is a rubber type sealant product.

But decorators mate is the c**p that was used before, looked good for a few years, then failed and cost weeks of work to remove from the entire house :/

 

[steveo3002]

had this bite me before , you want a solvent based paint like your thinners smelling rattle can primer or paint , give it a dusting over with that then paint it

 

[JOEPRO]

But decorators mate is the c**p that was used before, looked good for a few years, then failed and cost weeks of work to remove from the entire house :/

Never heard of ot failing before. Can only presume it is being applied too thickly or something there do you have any photos of the typical failures you has seen before? If there is something better I could keep it in mind for the next time

 

[rcx132]

Never heard of ot failing before. Can only presume it is being applied too thickly or something there do you have any photos of the typical failures you has seen before? If there is something better I could keep it in mind for the next time

It probably was too thick. The "professional" decorators applied it.

 

[Welderpaul]

PU sealer is the wrong stuff to use?
Proper decorators caulk is fine. Put it on too thick and it sucks back/shrinks and cracks.
Had a problem with rubbish B&Q own brand caulk, overpaint with a grey and it bleeds like hell.

I stick with Everbuild caulk, never had any problems with that

 

[rcx132]

PU sealer is the wrong stuff to use?

I don't know. I've Googled and the only reason I found not to use it is that it's a bit dearer and harder to apply. After finding that silicone never lasts around my sink I used PU sealer and it's outlasted the silicone three times over. It's tough stuff, and I haven't found any reason not to use it. I'll try @steveo3002 idea to use a different primer.

 

[Smallfry]

Even thick, PU will cure after a week or so. Try a water based acrylic primer, then top coat with oil based.

The oil based paint ....... was it from Wickes ?

 

[Shedendman]

I've used PU sealer in a small under stairs toilet as the original caulk just shrank after a few years, cracked and looked terrible. I removed the caulk, sanded everything, applied the PU sealer. The sealer claims to be over paintable but any oil based primer I apply to it just never cures, not even after a week. I thought maybe the PU sealer needs more time to cure so I wiped off the primer, and gave it more time. But problem persists. I've re-read the PU sealer instructions, they say nothing about what sort of paint can be applied over it, just that it can.

I've previously used the sealer on car projects and overpainted it with epoxy primer, which had no problem curing then.

TBH you couldn't have picked the worse PU sealer out there,use to use that PU40 a lot(cheap),but like you nothing would dry on top,tigerseal(expensive) not a problem,they do a puraflex 25 which is a tadge better,but again it needs to fully cure before you paint over it

 

[brightspark]

does it dry testing it on a bit of scrap without the sealer ???

 

[angellonewolf]

why are you using oil based primer ? water base stuff around now is very good cover for skirting boards etc

paint an hour later 2nd coat then top coat you can paint door frames and skirting in a day

i dont know about any one else but i find oil based stuff goes yellow quite quick

 

[brightspark]

why are you using oil based primer ? water base stuff around now is very good cover for skirting boards etc

paint an hour later 2nd coat then top coat you can paint door frames and skirting in a day

oil based is best on skirtings that back on to solid downstairs walls .all my walls are damp proofed and the skirtings are pine upstairs and architrives all mfd and coated with acrylic water based primer undercoat

 

[striker]

I use bedec msp satin white on all our interior woodwork. Sticks like s**t to everything. Water based so easy clean up. Touch prime with it where I've rubbed through sanding, then two full coats. It sticks to plastics etc so should stick to pu adhesives. Doesn't yellow. Can't recommend it highly enough. Not cheap though.

 

[Keith 66]

Polyurethane sealants often dont like being over painted for some reason, I have had similar effects when anti fouling over PU sealant, there the paint softened & melted the cured PU.
A similar effect can be seen on some epoxies (West 105 & SP equivalents) where oil based paints can simply refuse to cure. If a two pack epoxy primer is used over the initial coating the oil base paint will cure.

 

[angellonewolf]

oil based is best on skirtings that back on to solid downstairs walls .all my walls are damp proofed and the skirtings are pine upstairs and architrives all mfd and coated with acrylic water based primer undercoat

im sure in certain places there used for a good reason i use oil under coat for cheap stain cover as bin stuff is expensive but worth it as it can be painted in 45 mins where if using oil over night

 

[rcx132]

Grime sticks to water based paint and it soon looks dirty. Oil paint wipes nicely and looks better for longer even if it does go a bit yellow. I assumed that oil primer is best under oil paint.

 

[8ob]

I did the same in the mancave store room, ply lined and pu sealer between the sheets followed by a coat of oil based eggshell and it took a month to properly dry over the bits that had sealer, stayed kind of tacky for weeks.

Bob

 

[Smallfry]

No question that oil based paint is more durable, especially for external use, as water based does become grubby very quickly, as the surface seems to break down.

White oil based paint does need exposure to sunlight to stay white. If used in a cellar or cupboard, or places that are artificially lit, it does yellow. Don't know why, you need a scientist for that one !