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joeconroy 09-03-2008 08:36 AM

Brick haze on brick over slab patio
I have cleaned my brick patio on the 6 year old house I just bought; twice with pressurized water and twice with a 19% solution of muriatic acid. Looks great when wet and even damp but always drys to look covered with a diluted milky haze about the opaqueness of no fat milk mixed with 50% water. The bricks are laid on an extension of the slab the whole house is built on. The mortar is light color but otherwise looks and acts fine. The bricks on the adjoining walls look fine. Whats the problem and how do I fix it? Thanks.

jackpine 09-03-2008 08:49 AM

Can you apply a sealant that will give it a wet look?

joeconroy 09-03-2008 09:27 AM

Wet-look sealant
I don't know about covering it with a wet-look sealant. I don't know if any of the typical silicone type sealants will give it that look and not wear off from foot traffic for extended periods. I will give it a try on a few bricks as I do vaguely remember seeing one sealant that mentioned such a look. Would really rather know what the problem is first.

jackpine 09-03-2008 09:30 AM

Is the area exposed to the sun more than the spot that is not affected? Could the sun be fading the blocks?

joeconroy 09-03-2008 09:38 AM

No, some of the vertical walls are in direct sun but the patio is covered and shaded by trees so rarely receives any sun.

KC Brick Layer 09-06-2008 01:20 AM

Sounds like white scum to me. Ive ran into quite a few times where ive tried acid washing and get no results. There is a product made by ProSoCo called white scum remover. this is the link to there site.}

If that link does not work just go to and search for white scum.

ccarlisle 09-06-2008 06:32 AM

The problem may come from what your bricks are sitting it outside? uncovered? is it bare earth? plastic sheet? concrete slab? any or all three?

Knowing that would help to establish whether this is efflorescence or not. Pics would be nice.

joeconroy 09-06-2008 08:45 AM

Bricks sit on concrete slab
The bricks sit on a concrete slab that is an extension of the house's slab. The patio is covered by the roof of the house. What is your thinking about what the bricks are sitting on? Is it possible they are leaching up something from the concrete. And if so, what and how can it be stopped?

ccarlisle 09-06-2008 10:03 AM

Well, a well-done brick patio would have been made on 4 inches of concrete, itself reinforced and sitting on about 8" of crushed gravel. Assuming that was done, then the slab itself might have been treated on the surface with a sealer to prevent further moisture from coming up. Then bricks would have been mortared in a half-inch mortar bed.

The other variation is a dry-pack mud system that is used for shower pans...but yours isn't. There may be a 6mil plastic sheet put underneath the slab but this rare.

You might just have all that, and this makes the question of the white stuff a bit perplexing...but if you don't then efflorescence is excess moisture coming from below evaporating off leaving soluble minerals salts behind. Normally, it is a fluffy crystalline powder that can be brushed off when it is dry. Is that your case?

If not, then I might examine the use of muriatic. You say that like 1 part muriatic to 5 parts water? That's about right but I fear the muriatic is affecting the mortar in either the grout or the base and evaporating up and out, leaving alkaline salts behind, like silicates.

But if it's slimy or oily then that's another matter...

Tscarborough 09-06-2008 03:32 PM

First, you should never use muriatic on brick, second you should never use a pressure washer on brick.

What you are doing is driving the acid deep into the brick, and then when it works its way out it is pulling salts with it, and thus leaving a haze.

Provided that you have not burned the brick with the acid, you can use a proprietary cleaner to remove the haze, then seal the brick with a penetrating sealer.

Post a couple of pics, one overall and another as close as you can get it in sharp focus. Is the haze powdery or hard?

joeconroy 09-07-2008 04:50 PM

Steel brushing does not help

Thanks for your help. I think you have something in your last post. However, The milky white coloring on the surface of the bricks will not brush off. I brushed it with a steel brush and then cleaned it with a damp rag avoiding the mortar, and after it dries it looks the same milky white. However, if you chip off the surface of the bricks they look fine; not milky. Very difficult o figure out.

ccarlisle 09-07-2008 05:03 PM

OK that rules out efflorescence; trouble is now you're looking at an insoluble white salt the product of the reaction between muriatic and sand: silicates. Silicas are components of many bricks and closely related to sand. They react with muriatic, so muriatic is not recommended to use to clean bricks with...was once, but no more. Once they are insoluble silicates they are pretty hard to remove but there is a product mentioned by another poster called White Scum remover.

But beware, this is a highly dangerous product to use and if you do use it, please do everything the packaging says to do otherwise serious harm will come. No kidding. Like it'll eat through your flesh and dissolve your bone underneath. No kidding. :(

That product is called for because just like sand is insoluble and it's a silicate derivative, not much else either will dissolve it, except the acid in White Scum remover. Oh yeah, it'll also dissolve glass, so be very careful.:yes:

This is an oversimplification of the chemistry, but no exaggeration on the acid. No kidding. :no:

joeconroy 09-07-2008 06:18 PM

Pictures of problem bricks
3 Attachment(s)
There are three files of pics, the one with the wood shows the milky patio bricks and the ok looking bricks at the top half of the pic are the bricks of the adjoining wall that are not milky. The drying bricks pic shows how the bricks look when still damp. I believe there is water trapped between the slab and the bricks causing them to take many days to dry out.

KC Brick Layer 09-07-2008 06:45 PM


Originally Posted by KC Brick Layer (Post 155476)
Sounds like white scum to me. Ive ran into quite a few times where ive tried acid washing and get no results. There is a product made by ProSoCo called white scum remover. this is the link to there site.}

If that link does not work just go to and search for white scum.

Yup, saw your pics and like i said earlier....white scum remover. sounds like a silly name but thats the tech name for it.

joeconroy 09-08-2008 10:04 AM

Its on to White Scum Remover
KC and CCarlisle,

I read the specs on Prosoco's White Scum Remover and it sure sounds like what I have is "white scum". Sorry I did not read that earlier KC; I thought white scum was some sort of organic growth and I knew I did not have that. Anyway, I am sure going to try it. Thanks again.

PS, of course many still use muriatic acid to wash brick and and it did not harm the vertical (wall) brick I tried it on. I guess that is because it does not seep into and beneath the wall and so does not form the salts the same way it does on a horizontal surface.

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