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Our Victorian house was recently professionally painted - the job finished a few days ago. Last night it started raining, and this morning there are many places where the paint is now bubbling and blistering.

What could have caused this?

Note that:

  • Power washing did occur - but plenty of time went by (multiple days), in a warm and dry climate, for that to dry before painting started.
  • Some surfaces that are now bubbling were primed, others weren't.
  • There hasn't been rain in a long time, so the wood of the house was thoroughly dry.
  • The painters seemed to have been fairly careful about cleaning surfaces after preparing (scraping, filling, sanding) and before priming and painting.
  • Conditions were pretty ideal during painting - dry, mild temps (60s to 70s), little to no wind.

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Cooper
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    Wow. There must be something going on that isn't in your description. Everything you mentioned sounds ideal. The fact that even primed areas blistered is a real head-scratcher. What type and brand of paint? – isherwood Nov 21 '18 at 20:11
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    There's a fairly distinct line in the last photo where blistering ceases. Any idea what that's about? – isherwood Nov 21 '18 at 20:13
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    It also appears to be all the colors of paint and different underlying materials are affected. How odd. I'm no expert in the mechanics of paint bubbles, but it appears as though the material is off-gassing, maybe? It almost looks like paint stripper was applied. Be sure to keep us updated as things progress. What does your painter say? – Tim Nevins Nov 21 '18 at 20:50
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    Did they use a detergent with the pressure washer? – isherwood Nov 21 '18 at 21:02
  • If bleach was used in the cleaning process but not thoroughly rinsed it can cause trouble. – Kris Nov 22 '18 at 17:09
  • https://www.dulux.com.au/applicator/technical-advice/performance/blistering-of-exterior-decorative-paints. This has a lot of helpful info. – Kris Nov 22 '18 at 17:33
  • if you look at the picture of the round base, you will see that the blisters are in rows ,,,, the blistering appears to be caused by something that was applied with a paint brush – jsotola Nov 22 '18 at 19:15
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    Thanks all! Some details you requested: Brand of paint is Benjamin Moore Regal Select exterior, freshly purchased from local dealer. As the rain has continued, blisters have spread - there is no indication they line up with brush marks or other boundaries (like underlying primed vs. non-primed areas) - plus some blistering areas were sprayed, some brushed, and some roller brushed. No paint stripper was used, no bleach or detergent was used in the power washing. The previous paint, which was applied at least 8 years ago, had minor hairline cracks in some areas, but no blisters. – Cooper Nov 23 '18 at 17:41
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    My input is conjecture as well but I almost want to post it as THE ANSWER since based on all inputs, it is the ONLY thing that makes sense (to me). Nonetheless, it is conjecture.... The photos posted and all commments/answers seems to imply there is a chemical reaction taking place with the previous coat of paint OR biological (like algae feeding). This could be supported regardless of where primer was applied. Curious it seems worse where the rounded & tighter areas to reach (or harder to work areas) are. Seeming to imply lack of prep work (cleaning) applied in those areas vs. elsewhere. – noybman Dec 16 '18 at 16:06
  • The previous paint, which was applied at least 8 years ago- we'd need to know what that was, because obviously Benjamin Moore Regal Select exterior doesn't like it. – Mazura Dec 24 '18 at 21:43
  • Updates from the painter: After consulting with two different paint manufacturer representatives, my painter said the cause of the blistering remains a mystery. There was no manufacturing problem with the batch of paint, and all the prep and paint work was done correctly. The best guess anyone had was that the smoke (from distant forest fires) in the air during painting and drying, combined with the relatively brief period between the first and second coats, caused the second coat to not cure and adhere properly. Subsequent rain has not caused a reoccurrence of the blistering. – Cooper Dec 26 '18 at 22:05

1 Answers1

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I'm not an expert in the chemistry of paint so I did a little research and found this.

As the paint dries at different rates, it begins to pull and contract on one side, and stretch on the other, causing a bubble to form. The other way this can happen is if it rains on paint before it has dried completely.

Bubbles that occur on paint after it rains almost always happen very soon after the paint has been applied, and before it has had a chance to dry properly – often within the first 24 hours, although it could happen up to a week or more after the application.

Ref: https://www.homelogic.co.uk/exterior-paint-bubbling-after-rain-heres-what-to-do

Not sure if this helps but it seems to fit your description.

Christopher Lond
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