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If you do not protect the bricks from water ingression by covering the top of the newly laid wall and they become saturated by rain, the bricks will become waterlogged. This water will gradually dissolve the minerals in the bricks, cement and mortar and then these very fine salts, and mineral silicates will filter through the brick and crystalise on the surface as they dry. The bricks will begin to look dirty as though they haven't been cleaned. Often these stains cannot be seen when the bricks are wet, and they  reappear when.  This could take quite a few days. See images below.

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Other causes of these stains are poor bricklaying that needs excessive pressure washing which forces too much water into the bricks or the use of concentrated acid (below 10:1) which increases the osmotic pressure and draws the silicates, scum and salts to the brick face where they crystallize. Any excessive water exposure that saturates the brick can result in scum forming eg by down pipes and under any exposed areas that have been open to rain.

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These scum or salt deposits are not acid soluble and cleaning them with more acid will make them worse. Very toxic chemical treatments are required to clean mineral silicate scales which are similar to glass. The common names for them here are salts or scum  and in the USA and UK they are often called muriatic acid stains. Many people mistake them for efflorescence, but efflorescence can be easily removed and prevented once the water source is removed.

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Mineral salts can form different crystal structures as they develop and each crystal structure may require a specific chemical formulation so often one treatment may not work. We test and formulate appropriate chemicals specific for these difficult and hard to remove deposits and we try to avoid the use of Class 7 compounds like hydrofluoric acid whenever we can. Where possible we use alternative precursor fluoride chemistry first.

 

Hydrofluoric acid is in most of the commercially available mixes but this is an extremely dangerous chemical which should never be used on site without a SWM and the builders prior knowledge and approval. Builders should read the msds of the chemicals being used in case an accident occurs. Hydrofluoric acid is a class 7 toxin and an accumulative poison as well as a possible carcinogen. Exposure to Hydrofluoric acid can be fatal or you could lose a limb or your sight and in the worst case your life. It will also damage paint, eat rubber and etch glass so it should be used with extreme caution and with the OH&S managers approval. Acid proof protective safety clothing and double filtered breathing masks should be used.

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Cleaning well laid bricks with Barracuda 10K rather than acid helps reduce muriatic acid stains, acid burn and Mineral Silicates from forming. We also have the internal chemistry expertise to formulate a product to remove difficult and uncommon stains. See Stain removal photos in our gallery.

 

we specialise in treating mineral silicate or scum stains

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We recommend a site test first to try to evaluate the best chemistry to use. We also provide a written recommendation and quote. This is required because these products never crystallize under the same conditions, so the standard chemicals may not work well or could inappropriately applied by people without an understanding about what they are treating, how they should be used, or the toxicity and danger of these chemicals to themselves, other people, buildings, plants and animals.

 

This results in treatment failures and collateral damage to the properties, so the acid washers are often called back many times to re-treat stubborn and resistant stains. Each failure increases the cost and the danger to themselves, people in the location as well as the potential of collateral damage to the property being treated.

 

We usually remove 95-99% of the staining in the first few treatments and take appropriate steps to to minimize site damage. Recurrences of Mineral Silicates often called scum or salt stains will be limited provided the mortar is intact and not acid damaged or there have been no further changes on site to allow water ingression or other changes which allow these these salt deposits to form. We test the bricks with a moisture meter to decide on the optimum timing to treat or provide a root cause analysis.

 

If you want to understand more about Hydrofluoric acid which is the active ingredient in many commercially available products like "NoSkum" sold to remove these deposits, click on the link below. 

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We also have full PPE for each treatment as these chemicals are Class 7 toxins.

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