Preparing surface for painting


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Old 08-23-10, 11:56 AM
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Preparing surface for painting

Hi! I just started a project where I am planning in re-painting my balcony walls using a cement based paint.
The previous paintjob is cracked and at some points is chipped off the wall. The problem is that the surface is very big and it will take me forever to prepare it using just a putty-knife.
Do you know of an electric tool for this kind of job? I was thinking of using an electric sander (the one with the stick-on circular sandpapers).
Does anyone know if I can use something like that to remove the chipped paint? I will probably widen the cracks with the putty knife.
Many thanks
(By the way I dont live in Nevada I just had to fill something in the menu to post :P)
 
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Old 08-23-10, 12:30 PM
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Is this a concrete wall you're painting?
 
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Old 08-23-10, 12:35 PM
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No. Its a plastered and then painted brick wall.
 
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Old 08-23-10, 02:22 PM
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I assume it's a masonry plaster - stucco.

I doubt there is an easy method to removing the loose or failing paint short of paying someone else to do it A putty knife is probably the best way, a wire brush or any power tool would like remove the stucco along with the loose paint. The stucco would likely destroy sandpaper in short order.

Once you've removed all the loose paint, check and see if it's chalky. If it is, the best method to deal with it would be to flood's emulsa bond to the first coat of latex paint. A quality latex house paint should hold up better than most masonry paints.
 
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Old 08-23-10, 03:17 PM
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Hi! Thanks for the reply. I will probably try with the putty knife and maybe try with a sander too and see what will happen...
Hmmm I dont think I can get that paint additive here but there might be something similar, I might have a look when I get to painting. I was planning to apply a primer before painting too.
 
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Old 08-24-10, 04:23 AM
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A masonry conditioner is also very effective. If you can't find that, then use an oil base primer thinned about 5-10%.
 
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Old 08-24-10, 05:09 AM
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Oil based? Isnt that stuff toxic? I will be applying it outside but still I am a bit worried
Here is the plan so far:
1. Scrape any easy to peal paint and widen cracks with a putty knife.
2. Run a sander through all surfaces to provide a rough surface and maybe peel off some more loose paint. (Hopefully without ruining the sandpaper)
3. Fill all holes and cracks with putty.
4. Run the sander over the surfaces again to make flat.
5. Apply the primer. I am still not sure of what kind of primer to use, I was thinking of getting the "recomended primer" for the paint I will be using, not sure about which paint I will be using either. I wanted to use cement based because I like the texture
6. Paint 2 applications on the surface.
So far I am still scraping
 
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Old 08-24-10, 05:17 AM
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If the plaster is masonry you won't have much luck with sanding because the plaster will be tougher than the sandpaper.

What do you intend to patch the holes with? is it compatible with the plaster?

Unless you can remove the chalkiness, the type of primer is very important. Paint won't adhere to chalk! If there isn't any chalk, then most any exterior primer compatible with the top coat will be fine.

Paints aren't cement based although there are cement based coatings that can be or have coloring in them.
 
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Old 08-24-10, 06:08 AM
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Basically the surface that I was thinking of sanding is paint and underneath there is a layer of hard plaster (mortar?). Probably something like this>>>

http://www.isomat.gr/en/premixed-pla...shop.flypage5/

I wasnt thinking of sanding that deep though, just a run over the paint to remove some more paint then I can with the putty knife, and make the surface a bit more rough so the paint will stick better. I might skip that step though and run the sander after filling the holes first.
I will probably be using some ready-mix plaster to fill the holes, I have no idea if it is compatible with the underlayer. (I am not sure what the underlayer is).
The paint is indeed acrylic but its called "Cement paint" here for some reason. I thought it contained actual cement but I am not sure. Basically once painted it has a "rough" finish on the surface.
I had a look on the primers and I saw some oil based and water based ones. I will be surely using a primer as the surface will be very porous, possibly dusty as well. I would prefer to avoid oil based primers though because I think that they are toxic
 
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Old 08-24-10, 09:08 AM
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Ya, the chemical in oil base paint and the solvent needed to clean up or reduce the paint/primer is more toxic than latex paint. Solvent based primers as a rule, bond better than latex, if the surface to be painted is chalky - latex primer might not adhere good enough. It would be best to discuss this with your local paint supplier. I know here in the USA paint stores carry better coatings and have better trained help than your typical paint dept of a larger store.

Here, most masonry paints are more or less a cheaper grade of latex house paint. There are texture paints although I'm not sure if any of them are rated for exterior use.

The link you provided shows a premixed but not a ready mix plaster/mortar. You have to mix it with water. The technical data link talks of using an additive for surfaces where adhesion is thought to be an issue.

Again, I think your local paint supplier [providing he's well trained] or a local tradesman will be your best source of info since building practices and materials can vary in different locales.
 
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Old 08-24-10, 12:50 PM
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The paint that I am planning to use is something like this one:

K R A F T P A I N T S .GR

I know this brand and I think its one of the good ones allthough they seem to have many different types of paint. This one is solvent based so I would probably use a compatible primer for this one from the same brand.
The underlayer is something like that from the link but the putty I will be using to fill the holes will be probably something like this:

Xromatopolio e-shop

I cant find the product description in english but its a ready putty that I used before and it provides a very flat finish.

I would prefer to use water based then oil based because of the fumes basically, given that waterbased will be fine for use in the surface.
 
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Old 08-24-10, 01:37 PM
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I've never heard of that coating but their write up on it sounds good [not that anyone would write anything bad about their own product ] They also recommend a primer that is preferred with that coating.

Their literature said it was a low VOC solvent based coating. Your not likely to go wrong using the primer they recommend.
 
 

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