Masonry Magazine March 1971 Page. 18
4. Scrub.
Scrub down walls with a solution of one half CUP trisodium phosphate (Calgon) and a half cup household detergent (All) dissolved in one gallon of clean water. Scrub with stiff fiber brush only.
5. Rinsing.
Thoroughly wash off all cleaning solution, dirt, and mortar crumbs using clean pressurized water.
Procedure B.
When acid cleaning proves necessary, in certain areas, the following method is suggested.
1.
Make the cleaning operation one of the last phases of the job. Don't start before mortar is thoroughly set and cured.
2.
Dry Clean. A good dry cleaning saves time and acid. Remove large particles of mortar with wood paddles and scrapers before wetting the wall. In some instances, it may be necessary to use a chisel or wire brush.
3.
Presoak wall. Flush off all loose mortar and dirt. Soak the area to be cleaned with plenty of clean water just before applying acid. As long as the masonry is saturated, the acid and dissolved mortar will not be drawn into the face of the brick.
4.
Acid. Use a clean, stain free commercial grade of hydrochloric acid (muriatic). Mix, not more than, one part of acid to nine parts of clean water in a non-metallic container. Apply and scrub with a long handled fiber brush. Pour acid into water, not water into acid. Use only clean water. Note: Screen wire scrapers, under no condition, should be dipped or placed in the container of acid solution.
5.
Look out below. Be aware of the area below the cleaning operation. Keep all brickwork below the area being cleaned soaked with water and flushed free of acid and dissolved mortar. This acid scum, if permitted to dry, may be impossible to remove when the area is cleaned.
6.
Scrub. Scrub the brick, not the mortar joints. Use stiff fiber brushes, and wooden paddles when possible, and never allow metal tools to come in contact with the container of acid solution. Note: Metal marks on brickwork will be oxidized (rusted) by the acid solution, so be sure to wash off these oxidized areas before they dry, and stain the brick.
7.
Time and weather. Clean only a small area at a time. Preferably not more than 10 to 20 square feet. It may be necessary to clean even smaller areas when heat, direct sunlight, warm masonry, or warm dry winds increase the reaction rate of the acid and accelerate drying. This is a precaution against brick drying and sucking the dissolved mortar, dirt, and acid into the pores of the brick.
8.
Rinsing. Wash the wall thoroughly with plenty of clean water after scrubbing with acid, but before it dries. The acid solution in contact with mortar usually loses its strength after 5 to 10 minutes, and should be washed off. Dissolved mortar and unreacted acid must be removed to give a bright trouble-free wall.
Cleaning Light Colored Brick (Buff, Grey, Specks, and Pink).
Light colored brick are more susceptible to acid burn and stains than darker brick. Iron impurities in the acid, the reaction of acid with metal tools and metal marks produce yellow and brown colors on this type of brickwork. They can be streaked and the color dulled by failing to wash off the cleaning scum.
Procedure A.
Same as for Dark Colored Brick. Acid should not be used on light colored brick except in extreme cases.
Procedure B.
Same as for Dark Colored Brick, except as follows:
1.
Acid. Use the highest grade acid (chemical pure) available. Clean, stain-free acid as a general rule will be free from any yellow or brown discoloration.
2.
Acid. Use not more than one part high grade acid to fifteen parts clean water. When used, the acid wash should be neutralized as recommended for Removing Vanadium Stain, page 4.
3.
Scrub. Scrub with stiff fiber brushes and wood scrapers only. Avoid contact with all metals.
Textured Brick.
A texture or lack of texture will not conceal faulty cleaning. No texture can prevent dirt, mortar stains, or acid stains from dulling the natural color and beauty of the brick.
Smooth Textures.
Mortar stains and smears are generally easier to remove from smooth brick. As there is less surface area exposed, it is usually easier to presoak and rinse this type of brick. The unbroken surface is more likely to show poor rinsing, acid staining, and poor removal of mortar smears.
Rough Textures.
Most rough textures permit mortar in laying and mortar dirt in cleaning to penetrate deep down into the textures. In addition, the rougher textures present additional area for water and acid absorption. It is absolutely essential to use pressurized water in rinsing to remove all dirt and dissolved mortar from the texture marks.