Acrylic Paints - cracking and colouring

[WillC1423]

On a time critical job, so hoping for a very swift response here!

Due to us needing to prime, undercoat and top coat 7 doors in 2 days, and that not being possible with enamel paints, I decided it'd be a good idea to try acrylic paints, as they're gradually gaining popularity.

So, knotting compound applied and dry, we bought some Leyland Acrylic Primer Undercoat, assuming it was like the Dulux paint of a similar name. 1 application to prime and undercoat. First test it did a terrible job of covering the knots, so we dabbed all the knots, waited for it to dry, and then did 2 coats over the top. Doors look ok now, except on some of the doors have vertical lines of colour. Looks like resin coming through, but they're all perfectly vertical which is odd. Also, the paint has cracked over where knotting compound was applied.

Untitled

• WillC1423
• 14 Jun 2013
• 1

Ideas, causes, recommendations and solutions would be appreciated. I'm tempted to to just use knotting compound over the areas with colour, and then just re-coat and hope it doesn't crack again.

 

[misterhelpful]

The cracking over the knotting solution suggests that the primer may have been applied too thickly or not allowed to fully dry between coats. (You say you dabbed the knots to help cover them and the primer will not dry as quickly on top of the knotting.)
The perfectly vertical lines are likely to be resinous bleed from the the joints of the timbers made to use the panels - these areas can bleed even though there are no visible knots there - or could even be the glue, although that is unlikely.

You could sand the cracked areas and possibly fill, if required, with a fine surface filler before applying a coat of one of the Zinsser primers - Coverstain or B-I-N would work well in this situation, although the B-I-N will dry very quickly and may lead to 'flashing'. An oil undercoat would cover the patches too, but we all know about yellowing problems with oil based paints these days

I'm not a big fan of water based/acrylics yet because of this type of problem, but agree with the majority that they are gradually improving.

 

[Pigeon85]

Probably a bit late now but for future reference you would be better off using a seperate primer and undercoat.

Just a quick question, were these doors completely bare? Only ask as I recently done a job where the coverage was bad and then discovered they had been oiled.