Air bubbles when mud over paint.

 
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Old 02-04-2008, 11:12 PM   #1
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Air bubbles when mud over paint.


OK guys, me being the punchlist guy now I need a difinitive answer... how do I keep them damn air bubbles from causing me to put on 4-5 coats. I know why they come..so we don't need to go there.

Tried soap...no dice. Used brown bag durabond this am on a remodel project. We will see tomorrow.

If patch only needs one light skim its OK but if more coats are needed its bubble city.


Used to just be me and one guy doing all the work, now I bid, patch and run around a lot. Man things were easier back in the day!

Nate

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Old 02-05-2008, 02:05 AM   #2
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Re: Air bubbles when mud over paint.


I think that you may just have to accept it as a fact of trade. I would certainly like to know a cure, but this topic has been the topic of discussion on three separate forums and I have yet to read one so far.
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Old 02-05-2008, 08:22 AM   #3
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Re: Air bubbles when mud over paint.


Sorry cant accept it.
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Old 02-05-2008, 11:58 AM   #4
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Re: Air bubbles when mud over paint.


Well, It's not a materials quality issue under paper tape, so changing your materals won't help. 3M adhesive under cornerbead is always suspect under cornerbead for me, so it's never alone anymore.

You have to determine whether it is caused by coverage, tape condition, or open time.

A tried and true patch method is to use a sharpened hypodermic needle from an ink-cartridge refilling kit to inject some mud or glue behind the paper, then ride the broken edges of the crater to flush the surface.
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Old 02-05-2008, 10:07 PM   #5
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Re: Air bubbles when mud over paint.


No man the bubbles are from the moisture not being able to soak into the paint surface and having to come out of the surface....thus air bubbles. You are talking about a whole different PITA.

Nate

BTW the brown bag DB worked well as a filler of the bubbles after they have shown up. We will soon see if using from the get go will erase bubbles......prob not!
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Old 02-05-2008, 10:15 PM   #6
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Re: Air bubbles when mud over paint.


If you prime the area with an oil base primer first, the bubbles won't sneak up on you. Primer like Zinser 123. Or SW Pro block. It's not as good. The Zinser leaves the surface kinda porous feeling. But.... I hate to prime first before I start working on the spot. Pittsburg Paint makes a good oil, also.
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Old 02-06-2008, 12:35 AM   #7
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Re: Air bubbles when mud over paint.


Quote from another drywaller on another forum
"A painted surface is not porous like drywall paper. The change in the mud temperature effected by the warmer ceiling will cause the disolved air in the compound to outgas. On unpainted drywall, the gas is able to dissapate through the face paper and not form "seeds" (like you'll see on the bottom of a pot of water as it nears boiling point), but not so on a painted surface.

Over-whipping the mix might add to the problem, but I think the notion of mixing air into the mud is too frequently offered as an explanation for this phenomenon, and leads people on a fruitless (and potentially expensive) search for better mixing methods.

To stop this from happening, you would have to:

1- place the mud in a vaccuum to release the disolved gasses, or
2- heat the mud until it's warmer than the drywall and keep it warmer while working, or
3- Trowel repeatedly until the bubbles disappear (if the fill is shallow enough), or
4- Accept it. Sand off the bubble tops and fill."

This is by far the best explanation that I have read.
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Old 02-06-2008, 01:02 PM   #8
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Re: Air bubbles when mud over paint.


The worst air bubbles i ever ran into were solved completely by an additional skim coat (2 skim coats in total)

They really aren't that big of a problem. Just price for it when you bid the job.
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Old 02-06-2008, 08:28 PM   #9
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Re: Air bubbles when mud over paint.


Quote:
Originally Posted by bob16 View Post
The worst air bubbles i ever ran into were solved completely by an additional skim coat (2 skim coats in total)

They really aren't that big of a problem. Just price for it when you bid the job.
Its a little hard to price for punchlist. The Brown bag Durabond seems to be working the best. If you know how to leave a patch its not bad sanding either.

I dont buy the temp thing. Ive used hot water before and it still bubbles up.

I will try the zinser primer though.

Thanks for the replies guys.

Nate
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Old 02-06-2008, 09:50 PM   #10
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Re: Air bubbles when mud over paint.


You are some what correct that a painted surface is not porous, but a primer surface is. So the finish will adhere properly. You can tell the difference between the primer and the finish by the feel. The finish is slicker. The primer is rougher.
Nothing works completely every time. Too many variables. Brown bag durabond and a light skim sounds like a good bet. Maybe we could try thinning the mud with Pepsi or Mountain Dew. Just might work... After the fizz is out of the drink and at room temp. Ummm... another plan for tomorrow.
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