Painting problems


  #1  
Old 08-19-03, 10:42 AM
Jack Ruston
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Painting problems

Hi

I'm new to the forum and am looking for some advice on painting.

The problem I have is this...We are painting directly onto new plaster. The plan was to do one coat of white emulsion diluted with water, followed by two coats of normal emulsion. The paint is drying with a sort of textured surface in certain patchy areas...It feels slightly rough to the touch as opposed to the smooth areas which look fine. It doesnt matter how many coats we apply to these sections, brush or roller, they just look wierd! From directly underneath, there's no problem, but from accross the room the sections look patchy. We have tried using a coat of PVA to act as a seal followed by another couple of coats, and this has helped but not eliminated the problem. We are using a fairly cheap paint...Wickes trade white emulsion. The paint seems to be drying very very quickly.
Can anyone shed any light on this please?

Thanks very much

Jack
 
  #2  
Old 08-19-03, 11:43 AM
C
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Are you sure that the plaster is dry? If it won't pass a 24 hour moisture test, it is not dry and the paint will fail.

PVA primer is not suited for use on new plaster. It will fail as will the paint applied over it.

Thinning cheap paint to make it go further is false economy. It performs poorly, and requires many more coats to cover. This wastes the painter's time. Cheap materials give cheap results.

US Gypsum recommends acrylic, latex primer for new, dry plaster. A top of the line example of this would be Zinsser 123. Other manufacturers make suitable products. Over that, you can apply a top-quality, acrylic, latex paint.

The paint would appear to drying fast if applied to plaster that is not quite dry and it is reacting with the water in the plaster. This, too, will cause the paint to fail.

Hope this helps.
 
  #3  
Old 08-19-03, 11:57 AM
Jack Ruston
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Thanks for your help Chris.

The plastering was done about 2-3 months ago so you'd think it would be dry by now, especially in the serious heat we are having here in London.

The application of the mist coat (diluted emulsion) is standard practice here. The following coats are obviously not diluted.

I will talk to the decorator about that acrylic latex primer vs PVA advice. The problem occurred well before we got the PVA in so thats not our main issue, but its well worth bearing in mind forthe future...Thanks.

Is it possible that the paint has somehow been affected by heat? It has been unusually hot here. Perhaps its just cheap nasty paint. Our decorator has been using it for ten years with no problems, and we've tried different batches.

We're all stumped. I'm going to buy an expensive quality white emulsion tomorrow am and see if that behaves differently.

Thanks

Jack
 
  #4  
Old 08-19-03, 02:25 PM
rocketir
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can you define "Unsually hot". I see your in London and that could mean high 80's if I remember right.
I wouldn't think that the heat is the prob.
 
  #5  
Old 08-19-03, 03:39 PM
Jack Ruston
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over a hundred in the past couple of weeks.

Even so it doesnt sound too likely as a cause does it.

J
 
  #6  
Old 08-20-03, 08:35 AM
T
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Wicks matt emulsion although not the best you can get is usually fine..Sounds like you did everything ok..This has happend to me on occassion and I have never really been able to find out why..
I have tried thinning the paint out to make the emulsion roll smoother but with the same results.... Light hitting the walls makes the problem worse..The slightest shade and it disapears..!!
If you really cannot live with the finish even when the curtains are up ...rub down the walls smooth and seal them with zinsser bullsey 123. You can buy this product from a decorators merchant..Not B&Q!! Then try again with a good quality roller sleeve and Dulux trade vinyl matt....It a lot cooler now so we can eliminate that as the cause if done again.
 
  #7  
Old 08-20-03, 08:54 AM
Jack Ruston
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Thanks for that. It certainly sounds like the same thing. I found this reference on the web....

FOAMING / CRATERING:
Formation of bubbles (foaming) and resulting small, round concave depressions (cratering) when bubbles break in a paint film, during paint application and drying.

POSSIBLE CAUSES:
Shaking a partially filled can of paint.

Use of low quality paint or very old water-based paints.

Applying (especially rolling) paint too rapidly.

Use of a roller cover with wrong nap length.

Excessive rolling or brushing of the paint.

Applying a gloss or satin paint over a porous surface.



SOLUTION:
All paints will foam to some degree during application; however, higher quality paints are formulated so the bubbles break while the paint is still wet, allowing for good flow and appearance. Avoid excessive rolling or brushing of the paint or using paint that is more than a year old. Apply gloss and satin paints with a short nap roller, and apply an appropriate sealer or primer before using such paint over a porous surface. Problem areas should be sanded before repainting.


What do you think?

I reckon I will just have to sand it off where I can. I did some today. Took ages! All on the ceiling aswell. Oh well. Should I apply that stuff you recommended onto the fresh plaster?

Incidentally we managed to all but fix it without sanding in one room by applying a coat of PVA mixed with diluted emulsion. Strangely enough it just didnt seem to work in the other problem room. I am also finding that while it exists on the walls it is 'invisible' whereas the ceilings are the real eye sore.

Thanks again

Jack
 
  #8  
Old 08-20-03, 09:49 AM
T
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The solutions above dont really apply because as a decorator I paint hundreds of walls using the same roller and paint type..It only happens periodically..

Dont put the bullseye onto new plaster..Mist coat it first..Leave the bullseye 123 to dry for at least an hour or two before applying the Dulux trade...
I know its a lot of hassle but Im not sure what else to suggest...I had the same problem at work today but my customer doesn`t seem to have noticed...."What the eye doesnt see"...!!
 
  #9  
Old 08-20-03, 11:59 AM
Jack Ruston
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I really appreciate your advice and I'm glad I'm not the only one who's having this problem.

It s a slightly awkward situation because this is the final stage in a total refurb of a house, whereby we opted to do the decoration ourselves to save money. I realised in the first ten seconds that it would be a mistake to do this on my own, so I got a mate involved who is a professional decorator. He was the one who pointed out the problem initially and being a perfectionist is really pissed off about it. I called the builders I used for the main job for advice but of course they blamed him and had a good laugh. I of course dont see that he's to blame and all my own efforts to sort it have been in vain. Basically I want him to get on with the rest of the job and let me try to crack this room. I will follow your advice and see what I can achieve. When you say rub down, do I need to sand the cratering out completely? Also should I sand back to the plaster? Can I use a belt sander or is that likely to backfire in the form of a totally f***ed ceiling?

Thanks!

Jack
 
  #10  
Old 08-20-03, 10:59 PM
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Be careful with a belt sander..Its a bit over the top..All you need to do is smooth out the cratering..
The reason I suggest a primer like bullseye is because it will create a "shell" over the plaster which will eliminate plaster as the cause..
Always use a roller pole so that you can roll the whole wall reletivley quickly and evenly...
Let me know how you get on..
 
  #11  
Old 08-21-03, 07:52 AM
Jack Ruston
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Hi

Right I think we've cracked it. As you suggested we sanded down the whole ceiling and then repainted in Dulux trade. Its VERY much better. There are a few little bits we missed in the rub down but they're not an issue. Its so much better. The paint took a lot longer to dry than the Wickes stuff and according to cratering theory that would follow. I did get a tin of Bullseye 123 but opted to go without it in the end. I wanted to see if we could avoid that because its very expensive to give the whole house a coat. In the end we didnt need it. I will take it back. Thanks so much for your advice on this. Much appreciated!

Jack
 
  #12  
Old 08-21-03, 08:03 AM
C
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I'm glad it all worked out.
 
 

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