Archived

This topic is now archived and is closed to further replies.

Guderian

How To Remove Black Stains On Brickwork

22 posts in this topic

The concrete walls around my garden are finished off with small sandy-coloured decorative bricks. During the rainy season the north-facing wall has developed quite a lot of dirty looking black stains. This wall doesn't get much if any direct sunlight. The south-facing wall gets a lot of sun and does not have a similar problem.

post-51556-0-29896200-1353647820_thumb.j

post-51556-0-57206900-1353647845_thumb.j

post-51556-0-39624200-1353647866_thumb.j

I assume that these black stains are either fungal or bacterial - does anybody know which it is, and how best to remove them? Is there a fungicide or anti-bacterial agent sold for this purpose? I was thinking of using a solution of washing powder. A friend suggested bleach, but I'm afraid of that discolouring either the bricks or the coloured stone murals set into the brickwork. Do the big home stores sell anything suitable to clean these black stains off the wall?

Thanks for any advice.

Share this post


Link to post
Share on other sites

It looks like algae so something with Chlorine in it. You can buy granulated chlorine at a pool shop, mix some with water and spray it on.

Share this post


Link to post
Share on other sites

Easier and cheaper ( probably ) is standard toilet cleaner or something with acid in it . The toilet cleaner certainly does the job since it's got plenty of hydrochloric acid in it . This is a routine job on sandstone since it will develop everytime again . I got some sandstone in my bathroom and it needs to be treated regular with this .

Share this post


Link to post
Share on other sites

I would first try a small area scrubbed with bleach -wear gloves and goggles- as that is the cheapest. But, look out for the bleach staining it pink.

If that works, or if you try the helpful suggestions others have given, I would- once it is clean- apply 2 or 3 coats of PVA (Polyvinylacetate) as the stain is a mold which will find a porous surface easy to re-inhabit. PVA will seal the surface without leaving a sheen and would make it easy to clean again if necessary.

PVA is a white liquid which can be diluted with water up to 1:1 ratio. clean brushes with water.

Good luck!

Share this post


Link to post
Share on other sites

Thanks for the replies. I guess I'll have to test the bleach on a small inconspicuous area first to check for staining.

A friend suggested sealing the bricks, but he didn't mention PVA. Is that something you can buy easily in the home wares stores here?

Share this post


Link to post
Share on other sites

In 2008 we had sandstone facing installed on columns and exterior parts of our home which are exposed to rain. The builder gave us two choices in what to apply to the sandstone facing and we selected a product that would "soak into the sandstone, but not make the sandstone glossy". The lowest cost product of "Masonry Water Repellent" from where I shopped at that time, was "Dulux Silicone R 221". As I have expanded my shopping horizons I have seen similar "Masonry Water Repellent" at most every building materials store in Thailand, but you would have to rely on someone who can read Thai to see if what you buy keeps the sandstone the same color, OR if the particular product will give it a glossy sheen. When the OP is able to rid the sandstone facing of that black "efflorescence" (funny google ad pops up on this page) he should look into spraying some sort of "Masonry Water Repellent" onto that nice sandstone. Some of the cans in the store by MANY brands, show sandstone and /or bricks on the front of the metal container. It was NOT imported, it was not outrageous in price. We had a nephew "clean" the new sandstone in 2008 with a Makita blower, and then use a small hand held plastic spray bottle to apply the Dulux R 221 to every piece of sandstone. Of course , our written builders contract included the sandstone facing, but NOT the protection of the sandstone. Silly me to assume that was included in a building contract.

Share this post


Link to post
Share on other sites

Thanks. I'll take some photos to the local home stores and see what they suggest.

Share this post


Link to post
Share on other sites

Do you live in Thailand? In the UK there is a product called brick acid. If you do live in Thailand im sure there is something similar. Alternatively anything acidic should work especially if you use a wire brush to clean it. As mentioned always test a small patch first.

Share this post


Link to post
Share on other sites

Yes you can buy brick acid in thailand most builders merchants have it . I bought some before in my local merchants.Good idea about p.v.a. stops it happening for 3/4 years.

Share this post


Link to post
Share on other sites

I think brick acid is muriatic acid ? but BE VERY CAREFUL you need to neutralise it once applied otherwise it will eat away at your brick work and that will change the brick colour.

I'd try a mixture of water/bleach as your bricks are coloured, I use regular strength bleach on concrete and works like a charm. Should do the trick in 10 minutes and rinse .

Share this post


Link to post
Share on other sites

It looks like mold, similar to what my house and outside walls looked like after the flood last year in Bangkok. Weas did everybody else, used the toilet cleaner in the purple bottle. Did a good job claenib=ng and stopped the mold from growing, mold is a livce fungus.

Share this post


Link to post
Share on other sites

Thanks for the replies folks. Once the rains have stopped (and they seem to be very late finishing here in Pattaya this year) I'll experiment to see what works best.

Share this post


Link to post
Share on other sites

A pressure washer will take it off in a heart beat....and I've got some brick on my house just like in the OP's picture. I have a pressure washer I use around the house all the time...it takes algae/mold/black stains off bricks/rocks fast, easy, and without damage as it's just water under high pressure...no acids...no detergents....dangerous chemicals...etc. I fact most of my usage of the pressure washer is to remove stains off brick/concrete walls & sidewalks around my Bangkok house. I bought a Zinsana Andaman 120bar model for around B5,000 at Big C (they are sold at many locations like HomePro, Makro, Lotus, etc) after the major flooding last year as I had a lot of cleaning up to do...should have bought it a lot sooner based on how well it works in cleaning algae/mold/black stains. It's even fun to use.

Share this post


Link to post
Share on other sites

As Pib says, a pressure cleaner is the way to go.Be careful with any products since sandstone is very porous and absorbs easy.

After cleaning apply a water reppelent which you can have from Dulux as anothet poster said already, but also from TOA, Silca and many other brands.Look for the thins with a picture of natural stone.

Keep in mind that sandstone absorbs a lot and that this can be a costly operation if it involves a lot of square meters.

Share this post


Link to post
Share on other sites

  • Recently Browsing   0 members

    No registered users viewing this page.

BANGKOK 25 July 2017 07:40
Sponsors