Air bubbles when mud over paint.

 
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Old 02-04-2008, 10:12 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, 01:05 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, 07:22 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, 10:58 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, 09:07 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, 09:15 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 02-05-2008, 11:35 PM   #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, 12:02 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, 07:28 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, 08:50 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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Old 02-07-2008, 12:32 AM   #11
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Re: Air bubbles when mud over paint.


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Old 02-08-2008, 05:22 AM   #12
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Re: Air bubbles when mud over paint.


On painted surfaces what has worked for me is 2 things. Plaster weld on smooth (semi gloss over plaster) surface. On reg drywall mix ez sand a little watery throw a hand full of plaster on the hawk and mix together. Then prime the area with this mix larger then the work area. The trick is to get the mix to dry in minutes. This way the paint don't bubble and peel. When paint is wet it peels and bubbles. Don't give it the chance.
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Old 04-06-2008, 01:53 AM   #13
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Re: Air bubbles when mud over paint.


How bad are these air bubbles that you are coating them 4 or 5 times... ? Easy fixes are mixing the mud longer and more thorough, using a little more water to thin down the mud, and switching materials. I don't know what mud you have access to, but Beadex lite all-purpose is the least porous of the all-purpose muds that I have used. USG and Hamilton have more issues with air bubbles than Beadex.

Taping is interesting like that though because the muds I use may be terrible in your climate--tough to say. I have never heard of anyone having to touch up something 4 or 5 times to get rid of air bubbles. If you can't coat it twice, maybe touch up a couple spots and be done then something is not right.
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Old 04-25-2008, 08:53 PM   #14
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Re: Air bubbles when mud over paint.


WOW just sand the paint with an 80grit paper you won't get em if mud if mixed well enough
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Old 05-09-2008, 05:37 PM   #15
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Re: Air bubbles when mud over paint.


Quote:
Originally Posted by brdn_drywall View Post
WOW just sand the paint with an 80grit paper you won't get em if mud if mixed well enough
This was going to be my reply to. Sanding the paint has worked halfway decent for me. Still get some bubbles, but not nearly as bad. Gives the compound something to grab onto as well.
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Old 05-21-2008, 09:25 AM   #16
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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."--------((EXACTLY))--I used to run into this situation alot because my business is mainly repairs, and we are always going over painted surfaces. We have a rule here, whenever we go over a painted surface we NEVER use anything less than 5 or 20 minute quickset easy sand. Actally it's pretty simple. Air bubbles are gonna be an issue when going over a painted surface. Coat with the 5 minute. Do a light sand with a hand sponge OR my favorite is work the mud while it's setting up with a stainless steel knife...1 coat looks like glass. Pull a 2nd tight coat with 5((wipe on-wipe off)). After 2 coats of 5 minute easy sand it should look like glass.
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Old 06-20-2008, 08:20 PM   #17
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Re: Air bubbles when mud over paint.


Glass Finishers! I use regular mud, and pull tight on it for the 2th & 3rd coat. If you put a thick coat, your going to get bubbles. Scrap them off, and then pull tight.
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Old 07-11-2008, 01:01 PM   #18
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Re: Air bubbles when mud over paint.


Haven't seen any pinholes since i started using Bondcrete, it's universal bonding & sealing agent that works great for all my insurance work that i do.
By mixing the Bondcrete with water to the manufactures specifications on the can, then brushing it on with a paint brush directly on the painted surface allowing time for the bondcrete to dry, then apply hot mud over the brushed on bondcrete followed by a topcoat with no pinholes.
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Old 11-03-2008, 08:28 PM   #19
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Re: Air bubbles when mud over paint.


hey i have a little way of fixing your problem with bubbles over paint apply ur mud as usual and depending on how thick or thin u prefer ur mud let it dry for 5 to 10 min then wipe again with knife or my fav. trowel hope this helps
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Old 11-06-2008, 06:31 AM   #20
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Re: Air bubbles when mud over paint.


Ok maybe you might want to try this, remove the paint first by way of wallpaper stripper the 4" razor T handle one, I just did a kitchen ceiling that some body used Plaster Weld over paint failures, then they ran their mud, plain old joint compound with mesh tape. I scraped the whole kitchen ceiling took every square inch of paint off, then I primed the ceiling with Benjamin Moore's Block Filler, this stuff soaks into the plaster it doesn't lay on top. then I went and used M&H Ready Patch spackling, pole sand the ceiling then two finish coats paint.


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