Specification:Removing tobacco stains from concrete

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=GENERAL=

SUMMARY
 This procedure includes guidance on removing tobacco stains from concrete using chemical poultices. Safety Precautions:  DO NOT save unused portions of stain-removal materials. DO NOT store any chemicals in unmarked containers. EXCELLENT VENTILATION MUST BE PROVIDED WHEREVER ANY SOLVENT IS USED. USE RESPIRATORS WITH SOLVENT FILTERS. No use of organic solvents indoors should be allowed without substantial air movement. Use only spark-proof fans near operations involving flammable liquids. Provide adequate clothing and protective gear where the chemicals are indicated to be dangerous. Have available antidote and accident treatment chemicals where noted.</li> </ol> </li> See Specification:General project guidelines for general project guidelines to be reviewed along with this procedure. These guidelines cover the following sections: <ol> Safety Precautions</li> Historic Structures Precautions</li> Submittals</li> Quality Assurance</li> Delivery, Storage and Handling</li> Project/Site Conditions</li> Sequencing and Scheduling</li> General Protection (Surface and Surrounding)</li> </ol> </li> These guidelines should be reviewed prior to performing this procedure and should be followed, when applicable, along with recommendations from the Regional Historic Preservation Officer (RHPO). For additional information on poulticing, see 04455-02-R.</li> </ol> =PRODUCTS=

MATERIALS
<ol type="A">

For Normal Staining: <ol> Grit scrubbing powder</li> </ol> </li> For Heavy Staining: <ol> Sodium Hypochlorite (NaOCl): An unstable salt produced usually in aqueous solution and used as a bleaching and disinfecting agent.</li> Other chemical or common names include Bleaching solution*; Household bleach*; Laundry bleach*; Solution of chlorinated soda*.</li> <li>Potential Hazards: CORROSIVE TO FLESH.</li> <li>Available from chemical supply house, grocery store or supermarket, hardware store or janitorial supply distributor.</li> -OR- Javelle Water: Made by user, see 03710-02-S for guidance on preparation. <li>Calcium Hypochlorite (CaCl2O2): <ol> <li>A white powder used especially as a bleaching agent and disinfectant.</li> <li>Other chemical or common names include Chlorinated calcium oxide; Bleaching powder*; Calcium oxymuriate*; Chloride of lime*; Chlorinated lime*; Hypochlorite of lime*; Oxymuriate of lime*.</li> <li>Potential Hazards: CORROSIVE TO FLESH; FLAMMABLE (WHEN IN CONTACT WITH ORGANIC SOLVENTS). </li> <li>Available from chemical supply house, dry cleaning supply distributor, drugstore or pharmaceutical supply distributor, janitorial supply distributor, swimming pool supply distributor, or water and sanitation supply distributor. </li> </ol> </li> <li>Sodium Carbonate (Na2CO3): <ol> <li>A sodium salt of carbonic acid used especially in making soaps and chemicals, in water softening, in cleaning and bleaching and in photography; A hygroscopic crystalline anhydrous strongly alkaline salt.</li> <li>Other chemical or common names include Carbonate of soda*; Sal soda*; Soda*; Soda ash*; Washing soda*.</li> <li>Available from chemical supply house, grocery store or supermarket, hardware store, paint store, or water and sanitation supply distributor. </li> </ol> </li> </ol> </li></ol></li><li>Filler material such as diatomaceous earth or powdered talc</li> <li>Mineral water</li> <li>Clean dry towels for blotting the area after treatment</li> <li>Clean, potable water</li> <li>Accessible source of water, soap and towels for washing and rinsing in case of emergencies associated with the use of chemicals</li> </ol>

EQUIPMENT
<ol type="A"> <li>Glass or ceramic container for mixing the solution</li> <li>Wooden utensil for stirring the ingredients</li> <li>Wood or plastic spatula</li> <li>Stiff bristle brush (non-metallic)</li> </ol> =EXECUTION=

PREPARATION
<ol type="A"> <li>Protection: <ol> <li>Provide adequate wash solutions (i.e. water, soap and towels) before starting the job.</li> <li>Whenever acid is used, the surface should be thoroughly rinsed with water as soon as its action has been adequate. Otherwise it will continue etching the concrete even though the stain is gone.</li> </ol> </li> </ol>

ERECTION, INSTALLATION, APPLICATION
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<li>For Normal Staining: <ol> <li>Stir grit scrubbing powder into how water until it has the consistency of mortar.</li> <li>Thoroughly wet the concrete surface to be treated with clean, clear water.</li> <li>Spread the mixture over the stained area to a thickness of 1/2 inch using a wood or plastic spatula and allow to dry. Be sure to spread the poultice well beyond the stained area. The liquid portion of the paste will migrate into the concrete where it will dissolve some of the staining material. Then the liquid will gradually move back beyond the concrete surface and into the poultice, where it will evaporate, leaving the dissolved staining material in the poultice.</li> <li>When the poultice has dried, brush or scrape it off with a wooden scraper.</li> <li>Using a stiff bristle brush, scrub the surface with scouring powder and clean water to remove any residual staining.</li> <li>Thoroughly rinse the area with clean, clear water and allow to dry.</li> <li>Repeat the process as necessary to achieve the desired level of cleanliness.</li> </ol> </li> <li>For Heavy Staining: <ol> <li>Mix 1 part hypochlorite (diluted with 4 to 6 parts water) with diatomaceous earth or powdered talc to form a thick paste. <li>Select the amount of filler material to make a poultice of the required size. Add hypochlorite solution to obtain the proper paste-like consistency.</li> <li>The undiluted hypochlorite solution can be commercial household bleach (which is about 5% sodium hypochlorite) or 5% potassium hypochlorite solution or Javelle water. For guidance on making javelle water, see 03710-02-S.</li> </ol> </li> <li>Follow poulticing procedures in Section 3.02 A. 2-7 above.</li> </ol> </li> </ol>