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Do I need to get every bit of the paint off the brick/block before it's repainted? The house is 80 years old and some of the paint is coming off but there is green paint under the black paint that does not scrap away.
I started using a wire brush yesterday to scrap the paint off but the wire brush isn't doing the job. A lot of this paint seems to be permanent as it's so old. The pressure washer seems to get a lot the loose paint off so I thought about just using the pressure washer to get off the loose paint off and paint right over the old paint that won't come off.
Some people say use Muriatic Acid to clean the brick and then some say don't use it. Any recommendations would be great.
The pressure washer should take off the loose paint well enough. The paint that is old and will not come off is probably oil base.
Get off as much as possible of the top coat loose paint and repaint with oil base paint. Latex paint will not adhere to oil base paint. That's why it is peeling.
The more loose paint you get off, the better the new paint will adhere. Just be sure to use oil base paint.
If this is exterior use a pressure washer but be careful NOT to use too focused a tip -- no need to force away more material than necessary.
If this is interior then nothing that won't come off with a scraper is going to be a concern.
If is NOT A GOOD IDEA to use muriatiac acid as the whole cinderblock can be weakened, if this was a fired brick made of over backed clay that is a different story but regular cinder blocks are quite porous and acid will destroy them over time...
There are numerous alternatives to oil based paint that work quite well for these purposes. The product you want for very exposed exterior is probably going to cost more than those for interior / exterior trim --
Thanks for the advice guys. So I don't need to use an oil-based paint at all? So both an exterior acrylic primer and exterior acrylic topcoat will do the job? Sorry, as you can probably tell I don't do much painting.
The pressure washer should take off the loose paint well enough. The paint that is old and will not come off is probably oil base.
Get off as much as possible of the top coat loose paint and repaint with oil base paint. Latex paint will not adhere to oil base paint. That's why it is peeling.
The more loose paint you get off, the better the new paint will adhere. Just be sure to use oil base paint.
Great suggestion. If one was confused as to the composition of paint (oil, latex, etc.) how would one find out?
If one was confused as to the composition of paint (oil, latex, etc.) how would one find out?
Don't bother. Assume you have a wide mix.
With old surfaces the best compromise solution is to use a good quality sealer/primer, usually oil based,
to cover over everything and by that to provide a consistent underlay for the new finish paint.
Go from there.
If you are trying to cover a really dark color and end up with a "pure" lighter finish coat (and black is not as hard as some reds which can make even three coats of pure white primer look pink...) than I would recommend a true oil based primer, but the newer acrylics are really much easier to use and have much less odor problems...
Probably 90% of problems with paint not adhering have to do with the actual surface prep -- sanding wood too smooth or not removing every spec of dirt / oil are the biggies. Masonary paints typically are designed to hold onto rough surfaces tenaciously...
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