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FAQ's

  1. How do I remove graffiti from brick, block, concrete or stone?
  1. Why shouldn't I use muriatic acid to clean my brick?
  1. How do I determine which Diedrich New Masonry Cleaner to use for different types of masonry?
  1. What is efflorescence and what causes it.
  1. I have efflorescence on my brick, I pressured washed it off and a day or so later it came back worse than it was before. Why?
  1. How do I remove calcium carbonate from my masonry wall?
  1. My sprinkler system has been hitting my brick wall for a while and now I have a white haze on my brick. How can I remove the haze?
  1. Someone applied muriatic acid to my brick and now I have stains appearing on the brick. How do I remove the stain.
  1. I have heavy black staining under my windowsills that the Diedrich 101 Masonry Restorer wasn’t able to remove. What can I use to remove them?
  1. I have an old dirty brick or stone building. Why shouldn't I have it sandblasted to clean the brick or stone?
  1. What can I use to remove the old paint from my wooden house?
  1. What can I use to remove pigeon dropping stains from my building?
  1. What will remove oil stains and hydraulic fluid from brick, concrete and stone surfaces.
  1. What can I use to remove tar from brick and stone?
  1. How do I remove smoke and fire residue from brick?
  1. Which Diedrich products should I use to remove fire residue from, Granite, Terra Cotta, Sandstone and Limestone?
  1. I used Diedrich 101 Masonry Restorer to clean some old dirty granite, now I have yellow stains appearing, why?

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  1. How do I remove graffiti from brick, block, concrete or stone?

Diedrich offers two different paint removers that can remove graffiti without damaging the surface. The Diedrich 505 Special Coatings Stripper or the Diedrich 606 Multi-Layer Paint Remover can be used. Test samples should be conducted to determine which will be the most effective. If permanent markers have been used the Diedrich 505 will be the most effective.

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  1. Why shouldn’t I use muriatic acid to clean my brick?

Muriatic acid is just that, acid. It has no wetting agents or detergents to help control the acid and keep it on the surface of brick where it needs to be. Muriatic acid can cause bleaching and streaking of the masonry face, etching and removal of the mortar paste from the mortar joints, and cause a yellowish acid burn discoloration. If muriatic is used on brick that contains vanadium, iron, or manganese it will cause activation of these mineral salts resulting in yellow, green or black staining developing on the face of the brick. This is why brick manufacturer’s say “ do not use muriatic acid” to clean new masonry construction. Rather, they want proprietary blended hydrochloric acid detergents used. Additionally, muriatic acid will not clean old dirty brick. It is unable to break down and remove atmospheric carbon and pollution from masonry surfaces. Refer to Diedrich Restoration Cleaners for the appropriate product to use on the type of surface to be cleaned.

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  1. How do I determine which Diedrich New Masonry Cleaner to use for different types of masonry?

Red and other dark colored brick - DIEDRICH 200 LIME-SOLV.

Red, orange, tan, pink, glazed brick, structural tile, exposed aggregate, and natural grey concrete block - DIEDRICH 202 NEW MASONRY DETERGENT.

Black, white, grey, tan and chocolate faced brick; Limestone; Unglazed structural tile; Precast & exposed aggregate; Colored concrete block or colored mortar - DIEDRICH 202V VANA-STOP.

Burnished /Custom Masonry, concrete brick, slump brick - 222 CONCRETE BRICK & BURNISHED MASONRY CLEANZER.

Custom Masonry, architectural block, pigmented concrete surfaces and colored mortar - SPECIALTY MASONRY CLEANER.

Cast/Manufactured Stone, Sand Faced Brick or where hydrochloric acid based cleaners are prohibited – GREEN CLEAN 250

NOTE: TEST CLEANING SAMPLES MUST ALWAYS BE CONDUCTED TO DETERMINE SUITABILITY FOR THE SUFACES TO BE CLEANED.

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  1. What is efflorescence and what causes it.

Efflorescence is a white crystalline deposit that forms on masonry surfaces as the masonry dries. It looks like white salt crystals that if you wet a finger and rub it on the deposit then touch your finger to your tongue it will have a salty taste. If salty taste is not present what you may be dealing with is a carbonate type deposit (See Calcium Carbonate) Efflorescence is primarily cause by excessive moisture in the masonry. It is not unusual to see it on brand new masonry buildings. This is referred to as” new building bloom”. This is simply part of the natural drying process of masonry. As the moisture in the mortar and brick, block, concrete, or stone works its way out of the wall it brings with it the salts that develop on the surface as the moisture evaporates. In most cases the efflorescence will disappear on its own from the actions of wind and rain. Essentially it simply weathers off. If a building has an ongoing problem of efflorescence re-developing this is an indication of bad flashings, cracks in the brick or mortar, leaky gutters and/or downspouts, chalking or some other avenue for excessive amounts of water to enter the wall. The problem areas must be identified and rectified before removal of the efflorescence is attempted or it will keep reappearing. Before attempting to remove efflorescence make sure the masonry is dry. If masonry is not dry the efflorescence will reappear. A building that has re-occurring efflorescence problems might be a good candidate for application of a clear breathable water repellent to prevent a reoccurrence.

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  1. I have efflorescence on my brick, I pressured washed it off and a day or so later it came back worse than it was before. Why?

The last thing you want to do when removing efflorescence is to use pressured water. Pressure washing drives the moisture into the surface. The best approach for removing efflorescence is to use one of the Diedrich New Masonry Cleaners appropriate for the type of surface you are working with. The masonry must be dry before removal or the efflorescence is attempted. If not sure, a small test area can be cleaned and monitored for several days to see if the efflorescence redevelops. If it does reappear additional drying time must be allowed. Once the masonry has been deemed dry the following should be done. The surface should be pre-wet with water using a garden hose mist type spray and then the appropriate cleaner is applied by brush or low pressure spray and allowed to set for several minutes. Agitation with a stiff bristled brush for heavier buildups may be necessary. DO NOT USE WIRE BRUSHES. Rinsing should be done with a light garden hose mist type rinse.

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  1. How do I remove calcium carbonate from my masonry wall?

Calcium carbonate usually appears on a masonry surface as a light grey thick crusty type of deposit. Unlike efflorescence it will not have a salty taste. It is sometimes referred to as lime run. Generally to remove carbonate type build-ups the Diedrich 202, 202XX, or 202V will be needed and used in conjunction with a mason’s or rubbing stone. The surface should be pre-wet with water using a garden hose mist type spray and then the cleaner is applied by brush or low pressure spray and allowed to set for several minutes. The deposit is then attacked with the rubbing stone and essentially you will be grinding off the deposit. Rinse with a garden hose mist type spray then reapply cleaner as necessary. Several applications and attempts may be necessary to remove the deposit. Rough faced surfaces like split-faced block and wire-cut or textured brick will prove difficult for complete removal of the deposits. Be sure to keep lower areas wet and rinsed to reduce the possibility of bleaching or streaking. Multiple applications may cause a lightening of the color of the brick and mortar joints.

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  1. My sprinkler system has been hitting my brick wall for a while and now I have a white haze on my brick. How can I remove the haze?

The first thing to do is adjust the sprinklers so they no longer hit the wall.The haze is caused by minerals in the water being deposited on and absorbed into the wall. These deposits can be extremely difficult if not impossible to remove, especially if the situation has been ongoing for several years. There has been some success removing these deposits using the Diedrich 930 White Scum Remover. Test samples should always be conducted as the first step. There is a good chance that the haze cannot be completely removed because the minerals have been absorbed deeply into the surface and built up layer upon layer like a coral reef. You take a little off the top but there is so much behind it that it looks like nothing has been touched.

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  1. Someone applied muriatic acid to my brick and now I have stains appearing on the brick. How do I remove the stain.

Muriatic acid applied to brick and even some stone will activate vanadium, manganese and iron that might be present. Vanadium and iron will produce yellow or greenish stains that left untreated will darken to brown over time. Manganese will appear as dark oily looking stain.

Vanadium stains can be removed using the Diedrich 950 Stain Remover.

Iron and Manganese stains can be removed using the Diedrich 940 Iron & Manganese Stain Remover.

It should be noted that once these stains have been removed it may be necessary to apply a water repellent. Once these metallic oxides have been activated and the stain removed it is possible they may be reactivated by wind driven rains. The use of a clear breathable penetrating water repellent will help prevent this reoccurrence. Contact Diedrich Technologies for a recommended water repellent for your individual situation.

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  1. I have heavy black staining under my windowsills that the Diedrich 101 Masonry Restorer wasn’t able to remove. What can I use to remove them?

These are called black encrustation deposits. They can occur under windowsills, soffits, belt courses and other overhanging areas that are protected from the natural flushing action that occurs on buildings. These black encrustations can be removed using the Diedrich 808X Black Encrustation Remover. These deposits can also occur on concrete block, limestone, and sandstone surfaces. A neutralizer will be required to remove the alkaline residue of the 808X. The neutralizer can be the Diedrich 101 on brick and sandstone, 101G on granite and terra cotta, 707N on Limestone, or 960 on concrete.

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  1. I have an old dirty brick or stone building. Why shouldn't I have it sandblasted to clean the brick or stone?

The term “sandblasting” can now be somewhat of a misnomer. It used to mean using sand as the abrasive medium. Today it can mean using sand, ground up corn husk, walnut shells, or glass beads to remove something from a surface. Some contractors will say they don’t use sand, rather they use corn husk or walnut shells. While they may not be as aggressive as sand they still are abrasive methods. A couple of newcomers are soda blasting which uses baking soda and another system that uses dry ice. Both of these systems are not as aggressive as the above mentioned items but are still abrasive systems. Being an abrasive method it will remove the paint, dirt, rust or whatever but it will also abrade off some of the surface. It is for this reason the abrasive methods of cleaning masonry and stone are not allowed on historic landmarks and buildings. All brick have a face to it that is harder then the inner portion of the brick and gives the brick somewhat of a natural water repellent surface. Abrasive blasting methods removes this harder outer face and exposes the softer more porous inner portion. This softer inner brick will readily absorb moisture and the dirt that comes with it causing the building to soil more quickly and lead to freeze thaw damage. In areas where freezing temperatures are encountered this moisture will freeze, expand and cause the brick to crumble and deteriorate at an accelerated pace shortening the life span of the brick. Even in areas where freeze/thaw cycles are rare a brick that has lost its outer face will deteriorate at a much faster rate then an intact brick. Chemical cleaning with proprietary restoration cleaners or paint removers attack only the dirt and/or paint without damaging the brick face or the mortar.

While stone is a different story because it is the same throughout, abrasive cleaning will still erode the face of the stone. It will remove the surface soiling or paint but it will also remove some of the stone face at the same time. No matter how skilled the operator is, sandblasting will roughen the face of the stone. This roughened face will catch and hold moisture and dirt more readily and the building will soil again at a much faster rate. Again, proprietary chemical cleaners attack only the dirt and/or paint without damaging or altering the face of the stone.

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  1. What can I use to remove the old paint from my wooden house?

Diedrich 505 Special Coatings Stripper is the preferred product for removing paint from wood surfaces. This is because the 505 does not require neutralization before repainting. It works by lifting the paint from the surface. Because of this it will only remove a couple of layers at a time so reapplication may be necessary. If the paint build up is very heavy it may be possible to use the Diedrich 606 Multi-Layer Paint Remover. The 606 can be used to remove a majority of the paint and then switch to the 505 for the last layer or so or for touch-up work. If 606 is used the use of a neutralizer is mandatory. There are several Diedrich products that can be used as a neutralizer. They are the 202 New Masonry Detergent or the Diedrich 202V Vana-Stop. After the neutralization has been done pH tests of the wood will have to be done. Diedrich supplies pH paper strips with each pail of the 606. Most woods will require a pH reading of 8 or lower. The exception to this rule is cedar, cypress and redwood. These woods are acidic in nature and require pH levels no higher then 5. To reach a pH of 5 or lower it may be necessary to do two neutralization applications.

Wood must be allowed to thoroughly dry before repainting. Too often prepaintig starts within a day or tow after the removal process. If pressure washing has been used, several weeks dry time may be required.

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  1. What can I use to remove pigeon dropping stains from my building?

The safest method to remove pigeon and bird droppings and stains is using the Diedrich 707X Limestone Cleaner Pre-Rinse. Pigeon droppings can cause histoplasmosis, cryptococcosis, and psittacosis, which are fungal and bacterial diseases. Humans can acquire these by breathing in particles of the droppings when they have dried and become airborne. So whenever bird droppings are to be removed it is best to do so after they have been wet down to eliminate the creation of dust and airborne particles. The 707X will dissolve the droppings and help breakup the stain left behind in the brick, stone or concrete. The Diedrich 707N Limestone Neutralizer will need to be used as a second step to neutralize the alkaline residue from the 707X. Pressure wash removal of the 707X and 707N will be required.

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  1. What will remove oil stains and hydraulic fluid from brick, concrete and stone surfaces.

In most cases the Diedrich Aspir-Solv will remove these petroleum based stains In some severe cases where the stain is deep set and the Aspir-Solv alone is unable to remove the stain a poultice type system may be necessary. In a case like this, the Aspir-Solv can be mixed with the Diedrich General Purpose Poultice. The two products are combined to make a paste. The paste is applied to the surface 1/8 to ¼ inch thick. The paste is allowed to sit on the surface until it dries, usually about 24 hours. If the stain is extremely bad and deep set the paste can be covered with plastic sheets or aluminum foil for 24 hours. The covering is then removed and the paste is allowed to dry, again about 24 hours. The paste can then be scraped off and the area washed off with water. A pressure washer is preferable for this type of wash. There may be a slight wet spot looking discoloration left behind. This will usually disappear over a period of a couple days as everything dries completely.

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  1. What can I use to remove tar from brick and stone?

Diedrich 505 Special Coatings Stripper can be used to remove tar from masonry surfaces. If the tar buildup is extremely thick some preliminary steps may be required. If the tar buildup is ¼ inch or more thick it may be necessary to chip and scrape of as much of the buildup off as possible before using the 505. For these heavy buildups a simple trick is to use dry ice to freeze the tar. This makes the tar brittle and makes it easier to chip and scrape off the heavy buildup. As a note of caution, heavy insulated gloves will be required for handling the dry ice as it can cause major freeze damage to unprotected skin. Some individuals have used/recommended using heat guns or torches to soften and melt the tar. These are extremely dangerous methods that are frowned upon. While it will soften and melt the tar, the possibility of causing the tar to ignite and burn is a great. More then one building, historically significant or not, has been lost to fire due to the use of heat or open flame to remove tar and paint.

The Diedrich 505 should be applied thick and heavy. It can be allowed to remain on the surface for 25 to 45 minutes. A longer dwell time can achieved by covering the 505 with plastic sheets and allowing the 505 to dwell on the surface for one or two hours. The 505 and softened tar can then be scraped off and if necessary reapplied. If pressure wash removal is used the surface must be allowed to dry before reapplication. Multiple applications very well may be required.

Once the tar has been removed there may be a residual stain left in the masonry. To remove this stain the Diedrich Aspir-Solv or the Aspir-Solv and poultice system, as discussed in the oil stain question above, can be utilized.

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  1. How do I remove smoke and fire residue from brick?

The Diedrich 101 Masonry Restorer is usually the best choice. The 101 is a concentrated product that should be diluted with water. Test samples must be conducted to determine the proper dilution rate. STRONGER IS NOT ALWAYS BETTER. The surface to be cleaned should be pre-wet with water. The properly diluted 101 is then applied in a saturating application. It can be applied using a low pressure spray (pump up plastic sprayers) or thick bristled brush. The solution is allowed about a 5 minute dwell time and is then pressure washed off using a fan type spray tip.

It is always a good idea to determine, if possible, what was adjacent to the masonry when the fire started. This can have a bearing on what may be required to effectively clean the masonry. Here is an example. A residence had a fire. All but one exterior wall would clean. It was later determined, after talking to the homeowner, that there had been a plastic grass-like outdoor carpet next to this wall. This resulted in a plastic film being deposited on the wall. This film was just enough that it prevented the 101 from removing the soot. The Diedrich 505 was then applied to the wall to break the film, pressure washed off, and then the 101 was able to effectively remove the smoke residue.

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  1. Which Diedrich products should I use to remove fire residue from, Granite, Terra Cotta, Sandstone and Limestone?

Fire residue removal from Granite and Terra Cotta the recommended product would be the 101G Granite & Terra Cotta Cleaner. Sandstone can be cleaned using either the Diedrich 101 or in some cases the 101G may be used. Limestone cleaning will require either the Diedrich 707X Limestone Cleaner Pre-Rinse or 808X Black Encrustation Remover depending on the severity of the soiling. Both 707X and 808X will require neutralization with the Diedrich 707N Limestone Neutralizer. Refer to the individual product specifications for cleaning procedures.

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  1. I used Diedrich 101 Masonry Restorer to clean some old dirty granite, now I have yellow stains appearing, why?

Granite normally has high iron content. The yellow staining is the iron in the stone starting to oxidize. The product that should be used to clean granite is the Diedrich 101G Granite and Terra Cotta Cleaner. It is specially formulated incorporating a rust inhibitor to address those instances where iron may present in the surface to be cleaned. A couple of other instances where the 101G might be better suited for cleaning are white face brick and some sandstone that may exhibit the presence of iron in the stone by yellow, orange or reddish stains.

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