I have done remodeling for 37 years & finished drywall and repaired plaster using drywall methods for 35 years. There is an unsolved problem that comes up unpredictably on painted drywall or plaster that remains unsolved and unexplained. I call them “hot spots”. When the mud (I use only All Purpose) is applied there is a chemical “bubbling” resulting in scattered “pores” in a shotgun pattern. This can be minimized by priming, but not always eliminated. I called USG once and the technician diagnosed it as either outside air infiltration or air in the mud. From the locations and the experience itself I can’t accept that answer. There appears to be a chemical reaction going on and I have suspected (though not tested) something like aluminum oxide from previous sanding (we sponge). We don’t have this problem on new drywall.
Does anyone have the answer to this? I would appreciate it.
Replies
Is this problem more common where there is likely to be moisture present, wet walls, baths and kitchens? What kind of climate do you have there? Warm or cold? Moist or dry? Are there heating vents or wiring close to these spots? I have several ideas but these would just be wild speculation without any background.
We have a full range of weather here in Illinois. I hadn't considered moisture, but I just thought of some recent "hot spots" that could have been related to moisture and some that don't. This is one of the problems. I haven't been able to establish any constant.
Where are you from in Illinois?
We have people here from Alton, Champaign, and Springfield. I'm from Carlinville.Colvard's Logical Premises: All probabilities are 50%. Either a thing will happen or it won't.
Now you guys got me going. I've done a fair share of painting and always use TSP first to wash everything,including flat paint. But I don't do that when doing small drywall repairs. I will in the future because of another idea. Every room in every home, and I suppose, even in offices, have air born contaminants. I suppose in homes, there are more "oil" type air born contaminants, and especially from cooking. "Fish-eye" in painting has oil based contaminants as one reason for them, so I suppose, since mud is water based, at least in come cases, that might be the culprit as well.
I just thought of it - hair spray also. Or a light (not noticeable) coating from cigarette smoke. What else do people use from spray cans?
Sonny,
What comes in spray cans is almost unlimited from air freshener to flea spray for anmals and everything in between. I've also heard of problems caused by the contents of some aeromatic candles. I know my wife burns them all the time.
Don
Way back in the thread there was a reference to using Tide containers as water vessels to clean knives, etcs
As a retired Dentist, gypsum products are and have been inportant in my life. When we want to retard the set of plaster and other similar dental products, we use detergent, in minute quantities in the water. It can cause the release of H2S if in appropriate amounts.
Eureka, Tide?
regards
Stef
Stef,
Joint compound does contain detergents--that's why when cleaning fivers it bubbles up. I've never heard of, or seen anyone using a wetting agent as a retarder, but it makes sense. If there are any deeper reaction issues, I'm sure not aware of them.
Don
I'm from Macomb. It's been called forgotonia since you have to "tack" to get here.
I know all to well where Macomb is. My Wife lived in Rushville when we first met, and for the 2 years we dated. We used to drive up to Macomb to go shopping. My Sister was a Medhodist Minister in Mt. Sterling, Hull, New Canton, and Kinderhook for a while. So I'm definitely familiar with the area.
We're having a "HogFest" next spring in Carlinville - A get-together for folks from this forum. Here's a link to the thread about it:
HogFestWithout rocks there wouldn't be sand.
I suspect someone has used a heavily stearated sand paper and that the stearate from the paper has been imbedded into the plaster. The water in the mud is being repelled by this forming bubbles and causing the eyes or holes you are seeing. The reason you see a widely scattered pattern of shotgun blasts is that the sandpapers looses the most stearate when it is first used. So these blasts are the location that the new paper was put on the sanding pole but not removed by sufficient sanding action.
If this is the case. I'm making a blind guess here. A quick check with a plant mister and clean, no detergents, water might be used to identify trouble areas. A quick mist would soak into the raw plaster but bead off of the stearate contaminated areas.
You might try adding just a touch of detergent to the plaster to lessen the surface tension. Another possible method would be to wash the area with mineral spirits or other solvent to dissolve the contaminate. I understand that stearates are soluble in hydrocarbons and are in fact used as a minor additive to oil based paints.
Its a shot in the dark but I hope this helps in some small way.
If these sterates are present in sandpaper and/or paint that would make for unpredictable lurking. I will try the two potential solutions you suggested. We may have a chance this week. Thanks.
I don't know if we are talking about the same thing. It happened to me more than once. After I skim coated a painted plaster wall with All Purpose then put a primer on, everything seemed O.K. until I put the top coat on. When I put the top coat on there was a little time delay and then little bubbles in a shot gun pattern started to appear on the top coat which didn't go down after it dried. That's a mystery to me.
Tom
That's exactly what I'm talking about.
Mud can be over mixed and this can be a problem, but at the same time---take a new addition abutting up to an old plaster wall, tape it and the new drywall is fine, but the old plaster will have little bubbles appear. Some will pop, some will not. You can spend 5 minutes going over and over it with a knife and it makes no difference. But guess what---every drywaller and plasterer I know has asked this same question. It has to be some kind of chemical reaction, but who knows what. It's possible it could even be the result of a pre-existing chemical reaction like latex paint over primer over oil based enamel. Who knows???? Every drywaller I know would like to know the answer to this one. You know the old saying, "Been there, done that!"
Don
OK, on painted old drywall ( I do get this a lot more on the old plaster walls), maybe it is the water in the mix. The excess water would be able to seep into the drywall on the new but not on the old painted and would have to move up and out, creating the volcanoes.
I love a good mystery, but hate a bad job.
Gonna be following this thread..
Excellence is its own reward!
"The first rule is to keep an untroubled spirit.
The second is to look things in the face and know them for what they are."
--Marcus Aurelius
Here's my theory. I have absolutely no proof.
The water in the SR mud activates hydrates in the plaster left from the application years ago. Some tiny particles that never combined in hydration/curing.
I alway like to seal the old palster walls after washing with a bonding agent. That minimizes the effect you are describing and helps whatever kind of new patching or finishing skim coat adhere.
Excellence is its own reward!
"The first rule is to keep an untroubled spirit.
The second is to look things in the face and know them for what they are."
--Marcus Aurelius
Has happened to me only now and then over my 31 years using drywall compound.
Is it possible they are called by minute water droplets that finally dissipate and the pops or mini-craters are the voids left after the droplets dissipate due to the compound itself having set up enough so it can't "flow" into those mini voids.
A similar occurence happens sometimes with paint, but for a different, yet similar, reason. In the case of compound, I always thought it was due to excessive water in the mix or air bubbles from power mixing.
The entrained air idea may be it. using my bondin agent would change the surface tension enough to moderate that and let the air come out easier in troweling. The primer would be doing the same.
BTW, are we all talking the same thing here? SR mud over old plaster - right?.
Excellence is its own reward!
"The first rule is to keep an untroubled spirit.
The second is to look things in the face and know them for what they are."
--Marcus Aurelius
You could be right about the entrapped air, but it doesn't seem that way. On a extreem example there is a large amount of bubbling on the first coat. I can't believe there could be that much air in the wall or the mud. We don't mechanically mix the mud.
This happens on plaster and previously painted or papered drywall.
Practically all of our jobs are slick finish. We get the wall to a "B" level, prime with "First Coat", then do touchups with a bare light bulb, sponge and re prime. I have seen the "hot spots" survive both prime coats.
Thanks, Piffin, and the same to you. The reason I don't think it has anything to do with plaster is because I occasionally get it here in Naples, and all of the drywall repairs I do are on drywall. I often use 20 minute and 45 minute powered compound - Stay Smooth brand by National Gypsum. I get it both with the above and with premixed stuff in 5 gallon buckets.
The premixed, I keep in a one gallon container with a slight film of water after each use (like latex paint) to keep a skin from forming. When I use it, I mix it briskly with a paint stir stick as I do with the dry stuff to eliminate the lumps in the dry stuff and cause I'm always in a hurry with the premix - "This last coat and I can go outside and have a smoke while cleaning my tools."
Funny now that I'm typing about it. I carry a - I think it's a 1.5 - empty gallon Tide container in my truck for small water uses instead of locating a hose bib on these condos. It's amazing how efficient one can get at cleaning drywall knives, tray, and hands with only about 1.5 - 2 quarts of water.
Anyway, that's why I thought of either water droplets or air. Now that someone brought this up, it's gonna drive me crazy until someone figures it out. As for me, from now on, less water first. If I still get it, then less briskly when mixing. I'm sure it's one of the two. From my end, I'd rule out plaster since as I mentioned, I never run into it here with my repairs.
Edited 12/9/2002 12:32:38 AM ET by Sonny Lykos
Edited 12/9/2002 12:33:55 AM ET by Sonny Lykos
Hey Sonny, While you are here and I'm thinking of it,
Merry Christmass and hope this next year is good to you. When I think of the people who have meant something to me online, you are in the top ten. Thanks for your guiding light..
Excellence is its own reward!
"The first rule is to keep an untroubled spirit.
The second is to look things in the face and know them for what they are."
--Marcus Aurelius
Can't say that I remember having experienced this phenomenon on old drywall or plaster, but after reading all of these posts I have a wild and crazy idea about the potential source of this problem............I have donned my anti-tomato and stone suit, so here goes................furniture polish. ????? Most all of these have been silicone-bearing for many years and one spritz in the direction of the wall while standing close enough would contaminate it........ (carelessness and/or kids?) Silicone contamination is a problem for furniture refinishers as the finish will do a number called "fish-eye" which is related to the differing surface tensions. This just might be the same thing only it takes longer to appear because of the thickness of the compound.
Priming the area with the sort of thing normally used on a wall would help a bit perhaps, but sealing a revealed problem area with shellac prior to proceeding any farther would offer a much better barrier to any existing silicone.
(running for cover, spilling coffeee from cup)
Goldhiller,
From my experiences, I can't see where polish or silicon would have been the problem, but you are right about the potential problems polish and silicon can cause. They can screw up painting also. That wall behind the end table that got lemon pledged once a week for the last 10 years. Yep, Paint don't like it. This is one of the reasons a reputable painter will always tsp the walls before painting. It's for what they can't see, more then what they can see.
Don
Yeah, I know that this may seem like grasping at straws because that's what it is, but since I can't actually see what the referred to problem looks like, I'm just tryin' to offer theories that might explain it.....however wacky they may sound initially. And no, I never drink this early in the day. Boozing is reserved for after the end of all the days' business related activities. Usually this means after 9pm.
I do know that the silicone will migrate up thru layer after layer of susceptible applied material, but frequently the problem diminishes a tad with each subsequent layer. Plaster and drywall compound, I think, would also be susceptible to this migration. My thinking was that although this problem usually appears within ten minutes of the application of a furniture type finish or paint, it may take longer to show with thicker materials, i.e., you return an hour later and there it is. It could likely leave that "bubbling out-gassing" craters type look. Makes sense to me anyway, but that doesn't mean it's reliable.
We run into silicone contamination problems on fresh lumber as well, probably due to the use of silicone-bearing lubricants on the machinery handling the material or use of such near the wood while it's making it's way from tree to pick-up truck.
It'll be interesting to see where this thread goes, so if I do encounter the problem some day, I'll have some notion of the culprit and what to do about it.
Knowledge is power, but only if applied in a timely fashion.
I took a picture of a painted area that had this today at work. This was another finisher that used sandpaper. Now if somebody will tell me how to get the picture attachment in this little box.... I don't see the option.
Look at the bottom of the message posting page. You should see an option for attaching files. Click on that and follow the directions there. Browse to your pic if necessary and hit "upload". Wait until it tells you that it's done uploading (this can take a minute). You'll be returned to the file upload page again. If you have another pic to upload, repeat the process. When you're done, click done. Then click on "post". That should do it. Knowledge is power, but only if applied in a timely fashion.
Don't duck and run. Original thought is needed for difficult problems.
I don't think that's it either tho' because i get it even when there has been wallpapre on the plaster from day one with no paint ever and no exposure to these kind of pollutants..
Excellence is its own reward!
"The first rule is to keep an untroubled spirit.
The second is to look things in the face and know them for what they are."
--Marcus Aurelius
I'm going to try this again, I think I see the attachment option down there. Here goes:
Well, now. Congrats on getting the pic posting thing down.
That particular picture looks exactly 100% precisely like the silicone contamination fish-eye that I've seen for years on both clear coats and painted surfaces........and I can't help but notice the proximity to what I presume is a door or window casing. I've seen too many instances of a well-meaning house wife wiping down the fingerprints near the woodwork with that Pledge saturated cloth because it's right in her hand.
If I were you, I'd try sealing the surface with a couple coats of shellac, filling the holes with compound and repainting.
Silicone may not be the source of all these described problems, but this one sure has the signature of it.
My two cents.
Knowledge is power, but only if applied in a timely fashion.
Here's something that I should've offered in previous posts on this subject...........
If you have reason to suspect that a wall finishing problem may be silicone related and you opt for the barrier coats of shellac...............you're best off to spray these on rather than to brush (aerosol can for its handiness). Brushing can drag some of the silicone back up into the surface layer of shellac leaving you with silicone contamination again.
Also, shellac is an effective barrier against silicone and has excellent resistance to water vapor, but offers little resistance to water droplets. Therefore, it might well prove unwise to apply coats of shellac and then apply a thick layer of wet plaster or DW compound as it's possible it could penetrate the shellac prior to drying out and thereby release some of the silicones back into the surface layer. To be safe, if thick layers are going to applied over the shellac on a problem area, it might be wise to apply a coat of oil-base primer over the shellac prior to additonal mudding.
Shellac works well as a barrier coat on wood, but the porosity of some of these wall surfaces could be problematic in acheiving the same without applying additional coats.
If you try any of this, hope you'll post back and let us know if it worked.
Knowledge is power, but only if applied in a timely fashion.
Edited 12/13/2002 12:11:44 PM ET by GOLDHILLER
Have also experienced this bubbling problem in hot mud and lite topping when doing full skim coating over plaster. Worked side by side with an older fellow skimming and he had a bad shoulder so he wasn't using as much pressure on the knife, and he had fewer bubbles than I did (he was working 'under' me too!) We washed the plaster with TSP and rinsed somewhat well before we started. Had to scrape down the set up hot mud, then applied topping and had some problems filling in the scraped bubble craters. It eventually came out smoother than a babies butt, except for the mistake of trying to patch those remnant pinholes after pva primer, with lite-n-easy type filler. I actually prefer autobody spot putty for small holes especially in woodwork. The red-oxide color leaves something to be desired, but it sands out like nothing else.
As far as the fish-eyes from silicone, or oils. When I did car painting years ago you could buy "fish-eye remover/preventer" from the autobody supply store and it worked great when you came up against a nasty case of fish eyes spraying your first coat of catalized enamel, the fish eyes usually from improper cleaning off of the car wax, and also likely from using air tools lubricated with pneumatic oil.
Yes, I would concur. I've tried numerous products over the years in an attempt to conquer these problems when finishing wood or painting contaminated surfaces and one of the best was a "silicone remover" from an automotive paint supplier. It worked pretty well in some situations, depending upon how saturated the surface was. If trouble was still present, I then turned to the use of Sil-Flo, which is added to the finish to reduce its surface tension and bring it in line with that of the contaminated surface. I'm sure you're familiar with this product also. That too, works well in many situations, but not in all. There's a limit as to how much one dare add to the finish or it may never cure properly. I've pretty much come to the conclusion that whenever possible, the best approach is simply to seal any suspect surface with shellac first or at the first sign of trouble if you get blindsided.
I think I catch your drift about the fella with the bad shoulder……… he was dragging/forcing less of the silicone to the surface, if indeed that was the culprit in that situation. Makes sense to me.
I'm not sure just how effective TSP can be against this stuff on a porous surface and I hope I never have occasion to find out. Silicone-bearing furniture polishes/products are a banned commodity in this household. No Pledge or Liquid Gold, etc. allowed.
Knowledge is power, but only if applied in a timely fashion.
Ya, not sure about my theory with the older guy + bad shoulder, I guess I thought it might have had something to do with my creating air bubbles by putting too much pressure/working too fast with the knife..... and his less pressure/slower technique created less bubbles. Who knows......I seem to get bubbling even over sheetrock..............
Doesn't sound like anyone has hit on a definite for-sure cause or preventative for this. I think there's likely something to your notion about the difference between application techniques......at least if this problem develops on a brand new piece of rock. Difference in pressure might be involved or the difference of attack angle on the trowel and/or knife, cause when two guys stand beside each other applying the same material and one gets bubbles and one doesn't ...............I doubt it's the aftershave they used that morning.
Luckily, I don't have much of problem with this no matter the surface to which I'm applying. It's all in the wrist, guys. :-)
Knowledge is power, but only if applied in a timely fashion.
Fonzie,
Hate to tell you this, but from what I see, the job isn't done. The flashing on the bead gives it away. Looks like too much mud was used to make the job go fast. This should have had a couple of topping coats on it. A lot of drywallers brag about being able to tape and 2 coat. Makes for a lousey job, and this is what you see. I would almost bet that when this was taped, the finishers filled the tapers with mud, and then just filled the shirkage with the 2nd coat.
Don
Don C,
This is the way it was when we got here. We are reworking this finish job and repainting.
The problem I had trying any of the suggestions is this: as a "control" test I tried first just filling with all purpose mud. There was no further reaction in this case, so I couldn't try the paint thinner.
Let's say it IS air. This could allow several different sources with the same result. Air in mud, too much pressure, air infiltration, c o2 reaction, as somebody said. The reaction is one I know I have seen. I can't understand why a chemist from USG doesn't apply his stuff to this problem.
By the way, what is TSP??
TSP - trisodium phosphate. It's a cleaning powder. I routinely use it before painting doors and woodwork, and especially exterior doors. If you make a paste of it , it will act as a mild paint remover. Great stuff and is sold at most paint stores, HD and Lowes. I also use it when I want to reconditionmy brushes.
Fonzie,
I wouldn't want to even attempt speaking for a chemist, but lime and gypsum are some rare birds. When they go into solution, like most everything else they become something else, but when they cure and release their water, unlike most everything else, they revert to exactly what they were before going into solution. I don't pretend to even understand what all that means or how it works. But there is almost zilch that can prevent this from happening and thats why the chemists can really pinpoint the problem to this or that. There are just too many this's and that's. It's too the point where to some of this stuff there is a real science. Some of the high tech molding plasters have to be used in clean rooms, or darn near anyway. Almost anything is considered a contaminant. That could be humidity to ozone to cigarette smoke. I've even read of stories from antiquity of both mines in limestone and plastering in domes where the lime was so caustic that the curing was so reactive that it sucked all the oxygen out of the air while releasing carbon dioxide and killing people from sufocation in the process. There are just too many varibles and most are attempted to be dealt with through additives in the mud. Now days, it's mostly vinyl and vinyl acetate.
For the problems in your picture, I think I would first try to scuff up the surface with some 60 or 80 grit paper. I'd do this to help make sure new mud could fill the pockets and wasn't prevented from doing that because of the basic geometry of the pockets themselves. A good washing following that to make sure any dust and other contamination is gone, and then remud. Your bullnose in the picture has obvious hollows in it anyway, so it needs more mud. Around here, a hollow is what you see when you lay a 12 or 14 inch drywall knife perpendicular to a cornerbead. If you see light between the blade and the wall, that's a hollow. It means enough mud wasn't used to square and 90 the corners. Or whatever angle is being produced. Hope that makes sense. Usually it's a sign of hang and bang drywalling, or production work. The result of the old pick two of the three for the job you want--price, speed or quality. One of those 3 has to give on every job. HTH
Don
Don C.,
Thanks, that makes it more understandable that the lime and gypsum has unpredictable areas (like wood and about everything I guess). There's always another side to things.
We know this job needed a lot of work. Unfortunately, as you know some of the problems go back to the hanging. It came out pretty good I think. But I wouldn't be surprised if down the road some screws show up.
Thanks for the TSP explanation. I'll be looking for it.
I agree. There is suspicion of silicone but however no evidence . As I said earlier one problem may not be the same as the next one that looks identical. A lab would be needed, which aint gonna happen and past that its speculation at the best.
What I see in the photo is the result of fill coating anyway which is taken care of on subsequent skim coats that are of creamy consistency, thus filling the holes and other small voids left by the fill coats.
The job aint done yet .
Tim Mooney
Stop thinning your mud with Budweiser!!
T
Do not try this at home!
I am a trained professional!
Since Budweiser is not good for drinking, you don't want to waste it.
Tom
Both beer and urnie can be used as retarders in plaster. Tends to piss the crews off if they find out though if you know what I mean! haha It was a common practice a hundred years and more ago.
Don
"Both beer and urnie can be used as retarders in plaster", do you know how they work? Next time make sure you use the former and your crew will be happier.
Tom
Both beer and urnie can be used as retarders in plaster.
I find that if you pi$$ on the plasterer's or buy them to much beer it can slow the job way down!
TDo not try this at home!
I am a trained professional!
outgassing?
your coworkers must be letting out some preetty raunchy farts if it's bubbling up the mud on the wall!
While my silicone contamination theory may be all bull-plop, there's any easy way to find out. Next time you encounter this problem, allow any applied materials to completely dry and then lay down a coat or two of shellac. An aersol can of the stuff would be handy to carry and there'd be no brushes to clean. It only takes about twenty minutes to dry, provided your supply isn't over 6 months old or so and you're working at normal room temps. If it stops the return of the problem in subsequent coats...... you've found a cure that may work on future jobs as well. If it doesn't work.....it was indeed bull-plop.
I'm not certain that every problem being described here is from the same source....nor that there is one universal cure for it.
I'm almost beginning to hope I encounter this so I can experiment with it..........nah.
Mix up the mud better. It's air in the mud.
Are you using the light compounds???? Do you know what makes it lighter???
AIR!
We never use the light mud because we consider it too fragile and we find we can't force light mud dry with heat guns. It seems to have an insulating quality that won't let the heat gun work. (We don't force the taping coat, just pre fills, bed, and skim coats on small jobs without consequence). We mix the mud carefully, not pulling the masher out. The mud is consistent and the hot spots unpredictable. The outgassing reminds me of the reaction at the back of the baking soda submarine boat I got out of a cereal box when I was a kid.
Fonzie,
The gassing from that tub sub was carbon dioxide if I remember right, and that's exactly what the bubbles in the mud are. As mud dries and cures, the chemical reaction is the release of carbon dioxide. Carbon dioxide has been a bane to some trades since the trades began.
Don
Never like the light compound.
Tom
These bubbles are caused by entrained air as mentioned by Piffin - post #13. Believe it or not, you will have more entrained air if you do NOT stir your compound, especially if it is older or has gone through a freeze thaw cycle or left in the sun to cook. Obvioulsly, if you stir it with a mechanical mixer you can entrap additional air in the mix, but that's only if you are mixing it wrong. Keep the paddle deep in the bucket. After mixing, the compound (without the addition of water) should have the consistancy of really thick cake batter and be creamy smooth. We have a special D handle drill just for this. It's amazing how much time we save because the compound can be applied more easily.
A sealed plaster wall will exhaserbate(sp?) the problem because the wall is less absorbant and less FLAT. We unconcioulsy apply more compound to these walls.
If you apply too much pressure, with your trowel/ knife too flat, you will get this regardless of what type of wall you have.
Adding too much water to the mix will have the same effect because you can easily squeeze the water out with little pressure of the trowel/ knife. Bumps will appear and look like prickly heat. When you sand these bumps you will find craters underneath. Whenever these occur and are found once the wall is dry, lightly skim these areas with your trowel/ knife at a 45 degree angle. More bumps will appear but when dry and sanded they will disappear.
We used to use USG's All Purpose compound but have found better results with USG's Lightweight compound. It's not great before mixing, but once you mechanically mix it, it is like applying butter on toast.
Hope this helps.
Edited 12/9/2002 9:41:41 PM ET by Frankie
I'll go with that,
and it's really nice knowing that I'm half right even when I don't know what I'm talking about.
;-).
Excellence is its own reward!
"The first rule is to keep an untroubled spirit.
The second is to look things in the face and know them for what they are."
--Marcus Aurelius
You're right, Piffin. I'll take "half right" every day.
I don't know. I've been plastering and drywalling for almost 30 and I've discussed this problem with other plasterers, drywallers, reps andor chemists with National, LaFarge, USG and some smaller independents. It's a long know problem which no one knows the exact problem to, but I believe air flunked the null hypothesis long ago. It is a reaction of some kind, what--that's the question.
Don
well, that was the other half of my theroy. LOL Dangit all, I'm all right!
.
Excellence is its own reward!
"The first rule is to keep an untroubled spirit.
The second is to look things in the face and know them for what they are."
--Marcus Aurelius
The problems will never be solved for sure unless you know whats underneath. I have done drywall all of my working life. So we are both experienced.
The water and "air" from the mud exits through the wall first and foremost , unless it cant because of another finish that holds the two from penetration . The water is mostly gone in a skim coat in a few minutes on new drywall, where it will dry from the edges with a wet middle on previously painted work. I think that you are right in saying that there is a reaction . The reaction must be that all of the reaction is happening on the top of the surface since the bonding surface is resisting contact with water and air . I also think there is air in all drywall mud .
My unofficial findings are that both air and water are having to exit the surface with out help from the surface being coated. Thus giving the flash to the surface which is common in clear finishing .
It is the findings of the Breaktime Appeals Court that neither the Pilot , the plane used to distribute mud or the mud itself is in error.
My reccomendation is that you should be issued back your flight status with out further delay.
Tim Mooney
Tim,
Your comments are fine, but like Fonzie Stated to begin with, this problem also happens on never painted plaster. Except for maybe stucco, nothing will absorb water faster then plaster. So the drying processes are not the problem.
Don
Edited 12/10/2002 12:10:06 PM ET by Don C.
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Fonzie
Dec-8 11:00 pm
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Qouted first post 25502.1
I have done remodeling for 37 years & finished drywall and repaired plaster using drywall methods for 35 years. There is an unsolved problem that comes up unpredictably on painted drywall or plaster that remains unsolved and unexplained. I call them "hot spots". When the mud (I use only All Purpose) is applied there is a chemical "bubbling" resulting in scattered "pores" in a shotgun pattern. This can be minimized by priming, but not always eliminated. I called USG once and the technician diagnosed it as either outside air infiltration or air in the mud. From the locations and the experience itself I can't accept that answer. There appears to be a chemical reaction going on and I have suspected (though not tested) something like aluminum oxide from previous sanding (we sponge). We don't have this problem on new drywall.
I answered that post , which one did you read ? I have no experience with plaster at all, except in painting or repairing it . I also said that he will never know for sure unless he knows whats under it . Im not trying to argue with anyone , but you have to look at the problem for a solution and its impossible with out a lab . For your problem over plaster may not be the same problem as I described for sure. My answer is the most common result on a painted surface being finshed. That excludes all the other reasons it could be . We could be talking several different reasons that cant be proved.
Tim Mooney
Sorry Tim, never thought you were pursuing an argument. I was just saying that out gassing isn't an eitheror proposition, so it's not a process to be nailed down easily. It's just one of those topics that is filled with exceptions.
Don
Thats right .
Tim Mooney
I see this in new construction when you coat hot mud with pre-mix. No?
Funny I never had the problem in old work.
Just to ask you a question in the same vein. I am having the painter and the drywall company come out to our new home of eight months to review with the building contractor our problem. Seems that the drywall mud over the seams, nail holes, and taping at the wall/ceiling connection show through the flat latex paint job. We even applied another coat of colored paint by our own sub and it still is popping through. We used this painter on our last home and his one coat paint over existing white latex came out fine with no problems. He is coming to the meeting as well. What are the possibilities for this effect? It took 4-6 months for it to start showing after our painter rolled this pale yellow/beige color on. WADR. GW
Greg , that needs to be posted under its own new post . Just respect to the poster here , as its called hijacking a thread. I know you didnt mean to do that but think about if you were waiting on your thread to be complete with answers , and someone knocked it off track. Your question is another discussion that we would be more than willing to discuss.
Tim Mooney
I guess I just got lazy tonight. That is why I asked the original poster if he would respond, since he seemed to be an experienced drywaller who would know the answer to my question. Answering questions within questions on the old site used to be looser after many posts already addressed the original posters question. New threads are good, but I am to lazy tonight. GW
Edited 12/10/2002 11:14:43 PM ET by Greg Warren
Start a new thread. This is a dif. question and will complicate the answer process.
BTW the problem is not the paint. It's the mud job. Another coat of paint will only act as a temp solution.
Sorry Greg, I don't know. I have seen Kilz spotted in show through the finish coat with a different something. We are thinking that when doing slick finish the eye must be able to see a thousanth variation in unflattering light. That is why we get the drywall to a certain point and seal it off with First Coat. If you don't it seems anything you touch it with (including paint) causes a possible shrink back. We do our touch ups and sponge whisps with a bare bulb and re prime. That brings the job up to an A.
Thanks for the reply. Sounds like First Coat was never applied. It was a production job, and I believe that the painter only sprayed the drywall once after the texture was applied. GW
The first coat of mud has dried and thus, contains air. As the first coat absorbs moisture from the second coat, the air gets forced out. With drywall or any other pourous surface the air goes into that surface. If it is painted however, the air has to escape through the freshly applied coat, causing the bubbling.
The best and most efficient way I found to deal with this is to let it go ahead and bubble. Later after I've sanded and primed (mashing primer into the BB holes) I go around with a 6" knife and light weight spackle and fill 'em up. If the final paint will have any sort of sheen (satin, pearl, semiglos...), I go around and reprime those areas.
~ WebTrooper ~
I was wrong once and it could happen again.
Curious, What do you mean by "air".
"The first coat of mud has dried and thus, contains air. As the first coat absorbs moisture from the second coat, the air gets forced out. With drywall or any other pourous surface the air goes into that surface. If it is painted however, the air has to escape through the freshly applied coat, causing the bubbling."
I said that , but I couldnt give it away!
Tim Mooney
I confused by this. There is no air in dried mud. If there were it would flake off. OF course this is if I'm following you anyway. When gypsum and lime are dry the they have a "ite" name. When wet, they are "ate." When they dry or cure again, they revert to "ite." This is like carbonate soda that is used as a drink mixer. Let it site long enough, and all the carbon dioxide(same with plaster and mud) is released via a chemical reaction with the "air". When released, the soda is what we usually refer to as "flat." If mud and plaster does not go "flat" it will delaminate and flake off the wall. This is one of the difficulties of working with plaster. The finishing of this process is often mechanical, and if you don't know at what time to go back at the plaster, you're sunk. Too late, or too early, doesn't matter. Better living through chemistry has made some of the available plasters today not nearly as sensitive to this as others or traditional plasters. But then again, I'm still not sure what is meant by air. Plaster and muds don't just dry by evaporation. The oxygen is pulled out of the H2O to create the carbon dioxide. In hot muds, the rate at which this happens is chemically controled and that's how they work.
Don
"I confused by this. There is no air in dried mud. If there were it would flake off. OF course this is if I'm following you anyway."
You arent following me , but thats normal for me ! LOL!
In a fill coat application running recessed joints , or joints that are high grade such as the side of a butt that is bad , we leave a lot of mud in a" fill coat" Air and water in unprimed drywall will suck in to the drywall because that is the polarized reaction until dry. You are right in saying that dry mud doesnt contain air . It happens when the mud is still wet causing bubbles to the top in cases of deep fills . Mechanical or hand operations doesnt trowel that coat where its deepest. Later in skim coats it is troweled ; thus meeting the surface. Sometimes filling new drywall causes open air pockets in the mud , but they are never trapped as you are misunderstanding me. There is quite a bit of air in a box of USG Pluss 3. Of course adding water and mixing to a creamy state reduces the air , but in a heavy fill , I dont add much water if at all. Mechanical fill coats will have a small amount of water, not enough to release the air as its almost straight mud that is mixed .
Anyway, I dont worry about it because I know that well thinned coats will follow , filling the small voids.
Tim Mooney