Mist Coat Failure - Help Please with Remediation

[kgk]

I never thought mist coating would leave me in the wilderness, but I have a dreadful sinking feeling I have a more than just a small problem here.

I am in the the middle of a whole house refurbishment (an ongoing hell already several years in process) and have just finished mist coating two rooms.

An architect friend advised using the same brand and type of paint for misting as would be used in later coats. A decorator (who seemed to be doing good work) when out visiting an acquaintance said I might as well use the same paint for the mist coat if that meant I could by a 10 litre tub and that vinyl matt would be fine since my walls were skimmed well over six months ago.

The paint is Dulux Trade Vinyl Matt (PBW). That same decorator recommended 3:2 for misting (saying anything less would be way too thick for Dulux trade). I mixed a small batch, brushed it in. It absorbed well and seemed to do as it should ... into the plaster, not on the surface, only came away if scratching away the plaster itself.

For the full job, I brushed the edges and rollered the large surfaces. I tried to work fast, trying to make sure that the paint got worked into the plaster, and not just the water sucked out of the mix. It is a messy and miserable job as all know, but job done! Happy ...

24-36 hours later, concerned and no longer happy ... caught the wall with some low tack masking and off pops the mist coat. Ok, maybe it is a fluke. No, seems to happen easily. and everywhere.

So I waited another 48 hours hoping maybe the paint would cure a bit better. No joy. still just as bad. tape still lifts away the paint. It seems to take a bit of plaster with it (although not much since the surface looks reasonable underneath). Paint layer is also too thick; it is possible to scape / flake away where the tape has lifted.

In doing these large areas I was really surprised at the opacity of the mist coat, but then again it is trade I thought to myself at the time. Bonus? Or not? Did it go on too thick (yes, almost certainly)? Did the water still get sucked out too fast (probably with vinyl just sitting on top)? Did it really still need to be brushed in and was rollering a mistake (almost certainly, seems to have laid down much thicker and more on the surface)? Well, this is what spins in my mind as I think about how this may have failed so miserably.

SHMBO (but will not pick up a paint brush herself) has reached deep into her soul for a whole new glare that I did not yet know existed. (She, as am I, is fatigued by the project but she watches DIY programs and thinks that we should have been able to redo a complete 3 bedroom semi in a 30-minute episode, maybe 60 minutes if it is BBC prime time). I am rather disheartened to put it mildly.


As far as I know there were no problems with the preparation of the surface:

- thoroughly dry
- no pva was used in the plaster (to my knowledge), although it was used on the surface prior to plastering
- no pva (or similar) was put onto the plaster after
- plaster not glassy by any stretch of the imagination, indeed visibly porous
- mesh sanded to removed snots, etc after patching holes and trowel marks, etc
- wiped down and vacuumed to remove dust so as only leaving a very slight amount of dust on a clean latex glove swept across the surface

- thoroughly scouring various forums I now realise that I could have certainly done myself a favour by wiping down with a damp rag, but that seems to have been a 'nice to do' and unlikely to have been the main problem.

I have a feeling that the remedial work is going to be excruciating. (Alas, lining paper is a non starter here.) But, if you have real expertise in this area of problem / solution, please don't hold back. I can't have the paint failing the first time a child blue tacks a poster to a wall or a balloon to a ceiling.

I also understand that it is important to point out for those who will follow on into this thread to point out what I did wrong. (For one, no matter what anyone says, I'll never mist with vinyl again, no matter how dry the walls). However, what I really need most is help finding a solution.

Thanks for reading!

K

And, BTW ...

I am a great fan of the forums here and reading through them has certainly helped keep me clean up a few problems and keep clear of many others in the past too. So as a first time poster, a comparatively new registered user, and a long time lurker, let me say thank you to all who have contributed to making this forum such a wonderful resource!

 

[sparkwright]

The real test is if the second, thicker coat goes on well.

If, while you're rolling or brushing, the paint comes off, then you do have a problem.

 

[kgk]

The real test is if the second, thicker coat goes on well.

If, while you're rolling or brushing, the paint comes off, then you do have a problem.

Thanks, sparkwright, for taking the time to read and respond.

I can see that the problem would be further confirmed if it isn't possible to successfully offer up the next coat of paint, but I think if I am failing to really understand the full implications of your reply.

Surely if the mist coat isn't sticking the plaster, and even if later coats stick to the mist coat, then the paint is still quite likely to easily come off the wall (just as two layers instead of one). It still seems like building on a foundation of sand.

Like I said, maybe I don't understand how the getting a second coat on would in practice change the situation.

K

 

[phatboy]

Its pretty normal for tape to lift paint off the wall.

It sounds to me like your mist coating was fine, and you just need to paint it

(or where you have damaged the surface now with tape, fill and sand that.

I think you are over worrying, get a decent coat of paint on the wall, wait 24 hours, and check it - it should be fine.

 

[kgk]

Thanks, phatboy, for reading and replying.

Its pretty normal for tape to lift paint off the wall.

It sounds to me like your mist coating was fine, and you just need to paint it
.

I haven't experienced a problem with tape before, not even in the areas of this house we haven't started redoing (and most of this house was clearly a bodge job). So, my concern remains. But maybe it is paranoia. I don't know. Not my area of expertise.

(or where you have damaged the surface now with tape, fill and sand that.

I think you are over worrying, get a decent coat of paint on the wall, wait 24 hours, and check it - it should be fine.

It is easy enough to patch and carry on.

I am just concerned that if this does not work then all I have done is added to my costs (paint and labour for the additional coat) and further complicate remediation.

I'm not sure how to work with hoping it is ok as a strategy.

Cheers,

K

 

[footprints]

Not unusual for masking tape to lift even cured paint, it sounds like you did things correctly and assuming all plaster was fully dry you should be fine.

As they say in the Hitchhkers guide DON'T PANIC!! unless as said the roller starts taking off the prevoius coat you should be ok

 

[misterhelpful]

I think the problem has stemmed from using the Dulux Trade for mist coating. I would never use it for that task as it is way too expensive and so thick that it needs to be watered down 50/50. A diluted contract matt is a far better plaster sealer than a vinyl emulsion as it is better absorbed.
Having said that, the decorator you spoke to was right that there is no reason not to use a vinyl as the walls would have been fully dried out after 6 months so there shouldn't be an issue. It does just sound as if it has been applied too thickly, and there is no problem in applying a mist coat by roller, so maybe it just needed more dilution.

As the other guys have said, there isn't much you can do now - stripping back will be a nightmare and is likely to cause damage to the surface. If, when you start to apply the next coat, the paint does start to lift then you do have an issue. If this is the case, then something like Zinsser Gardz would help bind down the paint - you could even use it before continuing if you wish as this would give a good base for your finish coats but it may be over the top to do now.

Good luck.

 

[kgk]

DON'T PANIC!!

Fair enough, wouldn't change anything anyway. It is what it is.

Thanks, footprints for reading and replying with your input.

 

[kgk]

MisterHelpful, I very much appreciate you dropping in for a review of the situation!

I think the problem has stemmed from using the Dulux Trade for mist coating. I would never use it for that task as it is way too expensive and so thick that it needs to be watered down 50/50. A diluted contract matt is a far better plaster sealer than a vinyl emulsion as it is better absorbed.

Having said that, the decorator you spoke to was right that there is no reason not to use a vinyl as the walls would have been fully dried out after 6 months so there shouldn't be an issue. It does just sound as if it has been applied too thickly, and there is no problem in applying a mist coat by roller, so maybe it just needed more dilution.

I've never used vinyl for misting before (not that I've done this many times). But the idea here was that the cost wouldn't be a big difference for the two small rooms since this would make best use of a 10 litre tub which would be used (near) full strength for ceilings and covings, and that the opacity of the mist would make it easier to get cracking onto the final coats. So, intent was not too much difference in money, but some savings in time when I was under pressure to get the job done fast. Clearly false economy on both fronts.

I doubt that Dulux technical support would be of much help here, but the strange thing is that Dulux recommends 80/20 dilution. That brings trade paint close to a retail consistency, but still much thicker than a mist coat. The 60/40 I used seemed thin enough (thinner than single cream), but still it clearly failed to absorb correctly.

As the other guys have said, there isn't much you can do now - stripping back will be a nightmare and is likely to cause damage to the surface. If, when you start to apply the next coat, the paint does start to lift then you do have an issue. If this is the case, then something like Zinsser Gardz would help bind down the paint - you could even use it before continuing if you wish as this would give a good base for your finish coats but it may be over the top to do now.

I am hopeful that the next coat would not lift this first mist. It doesn't feel quite that dainty that it will pop off if I give it a dirty look. At least if the paint being rollered on is thin enough not to have serious suction / grab. Undiluted Dulux trade might rip it off the wall though. Perhaps this might be an argument for doing another thin coat on top?


On Tuesday I will give Zinsser technical support a call and get some further input from them (re: Gardz or similar) and report back here so that others might learn from my situation in the future.


Again, thank you for your advice!


Ken

 

[kgk]

On Tuesday I will give Zinsser technical support a call and get some further input from them (re: Gardz or similar) and report back here so that others might learn from my situation in the future.

I've spoken with Zinsser technical support; very friendly people and I certainly suggest that anyone with a technical problem painting consider giving them a call.

After being briefed on the details of the failed mist coat, they advised that if there was an unsound layer of paint that it should be sanded back.

As much as one might have hoped for a magic solution, Zinsser did not suggest using one of their products in this situation. They commented that their products (indeed any product) will primarily bond on top of the existing layer and not be able to penetrate to change adhesion to the underlying substrate.

...

 

[joe-90]

Pity that they are wrong eh?

 

[kgk]

Hello "joe-90", thank you for reading and replying.

Pity that they are wrong eh?

... Well, I can only report my understanding of what Zinsser told me.

However, your comment would seem to suggest that in your own experience (as does misterhelpful's above) that Zinsser tech's were too absolute in their advice to sand back and completely reject use of their products.

Perhaps you might elaborate on situations where you have had success with Gardz (or similar)?

Also, I'm more than happy to call Zinsser again. Any details from your own experience that might get the Zinsser techs mulling things over would certainly be useful. Who knows, perhaps on this last call I reached someone less familiar with this product / problem application.

Thanks, again

 

[phatboy]

I expect Joe is meaning you have ignored some of the advice given here, in favour of the supplier. Can't hurt to try and roll a bit of the wall can it?

 

[joe-90]

You over watered down the original paint and washed out the binder so are left with chalk. The Garz will bind it all together again.

 

[kgk]

@phatboy, @Joe-90 (indeed all) I apologise if I have left the impression with you or anyone that I have “ignored” the advice I have received here. I have been carefully considering it all (arguably, perhaps too carefully), even if I haven't launched into a course of action yet.

However, please have no doubt, I do really appreciate that you are all contributing your time and experience.


@Joe-90 – I hope you have not taken offense at my request that you elaborate on your experience with Gardz. I wasn’t throwing down a gauntlet or anything similar. Suppliers can be very conservative, especially on the technical support (as opposed to sales) side. Again, I was just hoping to get a better understanding.

As for the Zinsser’s understanding of their own product, we can see in the forums here with respect to Gardz that it has evolved over time. In one thread a poster had problems with PVA on their plaster and Gardz was suggested to them in the forums. When that poster sought further advice from Zinsser, they advised that they did not think Gardz likely to adhere properly over the PVA and suggested one of their solvented products instead.

However, move on in time and Gardz is now recognized by Zinsser for sealing over PVA problem plaster. Surely that came from professional painters, trademens, etc such as yourself pushing their experience back to Zinsser who then in turn can further reassure the nervous DIY folks like me doing their research after having something go wrong the first time? .


again, thanks