pinholes galore

dukewall

After repairing heavily cracked plaster walls, a Zinssar Stain Blocking Primer was used to seal the surfaces. We thinned premixed Topping Compound and applied a fairly thick coat of the thinned Topping Compound. Owner wanted Smooth Wall. So, after sand/vacuum/sponge/wipe we applied another medium coat of the thinned Topping Compound. Result: close to Smooth Wall. But, thousands of pinholes. We are using 10 & 12" knives to apply a skim coat. A lot of pressure has been required to fill the pinholes & to eliminate new ones.
We have experimented w/ very low mixing speeds to add water, as well as applying the compound directly from the box of Topping Compound without thinning. No matter what, we are still fighting the air bubbles & subsequent pinholes. Is it a mistake to be using Topping Compound to achieve Smooth?
Any suggestions would be greatly appreciated. Also wondering if adding dish washing soap to the compound undermines the bond of Drywall Sealing Primer

Darren@Partners

Dish soap (Ivory, not a detergent)might have helped over painted Sheetrock. But going over plaster, should have used a coat of PlasterWeld and then use a setting type compound. Then pinholes or "fisheyes" IMO are more from the paint than anything else. Several additives are available such as Dr. Smooth Mud, these products do work, but Ivory or even thinnned Elmers glue will do much the same.

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Bevelation

You might need to use the same method as minimizing pinholes over paint.

Apply, wipe off, apply again and wait one or two minutes before smoothing. Do a section at a time and alternate so that you're not waiting around.

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What do you add to powdered water?

dukewall

Thank-you for the quick response. Am unfamiliar with Plasterweld. I'll check it out. Curiously, the initial HEAVY coat of Topping Compound that was applied over the oil-based Primer Sealer (Zinsser) had NO pinholes. The pinholes only appeared during/after subsequent applications. Have moved toward the solution you suggest of applying a thinned coat of mud, wiping to fill the holes and returning after a minute or so to top it off with another thin coat. That seems to work okay. But, it sure takes a lot of time. I will see if local suppliers have some of the products you mention to help eliminate more pinholes from trapped air bubbles. Mostly, appreciate your comments tremendously. Duke

dukewall

Thanks for your feedback. The method you suggest seems to be our only hope, at this point. It is helpful to know that someone else has encountered this problem, before. I believe that my assistant was a little too ambitious in going for too thick an application of the second coat of compound we applied.
Once the pinholes were created, there was no turning the clock back. Duke

Bevelation

^Having gone too thick wasn't the problem. Whether you use setting compound, all purpose, or filling mud, they'll all coat smoothly over paint, and bubble out on second AND subsequent coats.

I state this firmly because I have consistently dealt with the same issue each time I work on patches overtop of paint.

The only time I haven't had pinholes is touching up on new construction where the latex paint hasn't had time to fully cure.

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What do you add to powdered water?

rockdaddy

hit it with 20 minute and sand smooth.

Whitey97

The products that Darren mentioned are all featured in one way or another in "Walls and Ceilings" a drywall/paint mag. check it out.

dukewall

Thanks for hangin' in there with me on this problem. It really helps to have the advantage of your experience without having to suffer through trial & error w/ each an every consideration. What still eludes me is this: What is the actual phenomenon occurring, here. Why do the gas bubbles seek escape on all but the first coat (no matter what thickness, I gather) over a painted surface? Is this related in some way to the moisure of subsequent coats absorbing back into the dried compound they are being applied to? Some blogs suggest what on the face of things sounds like just the opposite! Along the lines of: bubbles can travel in no other direction in compound placed directly over a painted surface than to the outside atmosphere. Wish I could think like an air bubble.
Roofers claim to track leaks by thinking like a drop of water. Would hate to imagine what a Plumber tracking a sewage line leak has to think like. I happen to be a General Contractor. We don't think; just wander around the jobsite in a daze (waiting to be paid or enter conflict). Hope this revelation doesn't get me kicked off of the Drywall Talk forum. The info I'm gaining is far to valuable.

dukewall

p.s. - Are the Steelhead running, yet?

dukewall

Hi. I spoke with a Tech Advisor from USG earlier today. His suggestion was to try using Easysand 90 the next time around. What would be the advantage of using a 20 minute setting compound, other than the speed at which it would be ready to sand? Is it customary to apply a thin skim coat with 20 minute?
Thanks for taking the time to advise me. The way we are getting around this problem is to trowel-down 2 thin skim coats (hope my terminology is correct).
We add sufficient water to premixed Topping Compound so as to put enough pressure on the blade to dispurse the air bubbles. This is time consuming. But,
it looks like we might end up with a very nice surface, afterall. Here's hopin'...

dukewall

Thanks. I inquired at two of the largest Drywall Supply outlets today re those products. They don't carry 'em. Where can I get a copy of "Walls & Ceilings"?

Bevelation

The 20 minute would be sandable in about an hour. But if you have a lot of area to cover yet, 20 minute stuff might be a pain with mixing batch after batch and trying to get it all on before it sets off. I'm not a fan of setting compounds, but that's probably mostly because the selection in Western Canada leaves a lot to be desired.

If I need a third coat on my product, I stick with "slow set". That's just my preference, though.

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What do you add to powdered water?

Bevelation

I don't know if they even run up this far. I just moved up to Northern BC from near the coast. I'm an ocean fishing kinda guy.

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What do you add to powdered water?

Darren@Partners

Duke, google Walls and Ceilings or Construction Dimensions. Or ask your supplier or rep. for a copy or subscription card. Both are free, and both are fairly useless except as a product guide. Most of the articles tend to ignore the current market conditions, basically fluff.

WeldCrete might be your region's version of PlasterWeld. Dr. Smooth Mud might also be found as Magic Mud Mix or a similar name. The USG rep will not recommend these additives. Neither would fully elimate fisheyes over latex. The hot mud "piss coat" is the best solution for your situation, followed by a drying type mud. We also usually pole sand the latex first.

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dukewall

I live near San Francisco. We used to have a fantastic Salmon fishery. It has gone to Hell in a hand basket. We also get Stripers & Halibut, some Lingcod, etc. It is hard to beat ocean fishing. The fish are bigger/tougher. But, the beauty of a wild river and a hot Steelhead is also quite an experience. Thanks

dukewall

Had a conversation this morning with an Outside Rep. from Westpac. He gave me a gallon jug of "Miracle Mix" to try. It really helps to dispurse the bubbles.
Since I am not doing production work, there is the liberty to take a little bit of additional time. Miracle Mix helps to keep the mud "open". That extra time is of great help to relative amateurs, like us. Many of the suggestions offered by the Drywall Professionals on this site have been a Godsend. Thanks so much!!

detroittaper

Duke, I believe you have answered your own question. The guys are correct in suggesting you plasterweld the wall first. You have to seal the wall before you mud over it. To understand why your getting the airbubbles after that, you have to understand how mud works. Lightweight or topping mud hardens by the moisture evaporating out of the mud. If the moisture can't go in one direction (a sealed wall), it goes the other. This creates air bubbles in your coat. You'll really notice this when you mud over a primed wall. Setting compound (such as durabond) chemically hardens, then dries. You'll achieve much better (less bubbles) using durabond (easysand!) over primed/sealed walls than regular mud. If your doing small patches, a hair dryer works great for activating/drying durabond. Great for doing multiple coats and sanding the same day (same time=save $$).

joepro0000

a hairdryer, try a heatgun. Much faster!