Paint not adhering?

I have a couple spots where an ultramarine burnt umber mix had some “bubbling” where the paint appeared to not adhere to the panel.  That paint is five weeks old on the panel.   I scraped off the pain wiped the panel with a paper towel.  
But now I see where the edge where I reapplied the paint looks dull.  And I seem to have some particles in the new painted surface.
I guess I need to scrape, clean and reapply again?


  • That's odd. Looks like something has contaminated the surface. I would suggest scraping off, cleaning the surface and starting again for that area.
  • a) What sort of timber and could it have been contaminated?
    b) Size - if timber was it sealed? (Or was it ACM?)
    c) Ground/ primer? The dull edge suggests underbound in oil so sounds like oil may have been absorbed into the ground or board if timber? Alternatively could there have been moisture beneath?
    d) Did you use a medium or solvent mixed that may have been uneven?
    My own recent problems with adherence were that the Gamblin oil ground was slightly thick and formed an alkyd oil film - so no tooth. I also used liquin which exacerbated the problem. So the ground needed sanding or the paint refused to adhere - although it formed ripples not a bubble. But I'll never again paint over a ground without checking that texture.
  • @Abstraction @Richard_P it’s ACM.
    the ground is Holbein oil ground.  The paint is Geneva.  The panel is 24” x 36” and these are the only two areas where it happened.  Could be the surface was too smooth.  Or maybe some contamination after the ground was applied.
  • GTO

    After a light sand for tooth a wipe over with isopropyl alcohol will remove any fingerprints from ACM.

  • GTOGTO -
    edited January 16
    Thanks @dencal that cleans up great.
    I think the dull edge on the old paint when I apply the new paint is because the film on the old paint is not dry enough.
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