Designation: C1515 − 14Standard Guide forCleaning of Exterior Dimension Stone, Vertical AndHorizontal Surfaces, New or Existing1This standard is issued under the fixed designation C1515; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (´) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide describes materials and procedures whichmay be used to clean dimension stone exteriors as well as theconditions under which they may be used. It is intended to aidowners, maintenance supervisors and building managers, ar-chitects and engineers, and contractors in cleaning verticalexterior dimension stone on commercial, residential and insti-tutional structures. This guide may also be helpful to those whowish to clean stone masonry on bridges, retaining walls, ramps,and plazas, and free-standing stone objects such as statuary,memorials and grave markers.1.2 This guide relates primarily, to routine maintenance ofthe surface finish of exterior dimension stone. The techniquesnoted herein may not be appropriate or cost effective withregard to restoration of disfigured, severely soiled or stainedstonework, or of stonework of particular historic importance.In cases where staining occurs on surfaces which have cultural,civic, historic or architectural significance, consultation with aspecialist is recommended.1.3 The user of this guide should also obtain and have onfile at both the job site and the office Material Safety DataSheets (MSDS) describing the nature of all chemical productsutilized during the cleaning process.1.4 A file of literature from the manufacturers of all prod-ucts involved within the scope of each project should beavailable for reference.1.5 These procedures are not intended for interior stone-work.1.6 This guide offers an organized collection of informationor a series of options and does not recommend a specific courseof action. This document cannot replace education or experi-ence and should be used in conjunction with professionaljudgment. Not all aspects of this guide may be applicable in allcircumstances. This ASTM standard is not intended to repre-sent or replace the standard of care by which the adequacy ofa given professional service must be judged, nor should thisdocument be applied without consideration of a project’s manyunique aspects. The word “Standard” in the title of thisdocument means only that the document has been approvedthrough the ASTM consensus process.1.7 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.8 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory requirements prior to use.2. Referenced Documents2.1 ASTM Standards:2C119 Terminology Relating to Dimension StoneC503 Specification for Marble Dimension StoneE1971 Guide for Stewardship for the Cleaning of Commer-cial and Institutional Buildings3. Terminology3.1 Terms used in this guide are defined in TerminologyC119.3.2 Definitions of Terms Specific to This Standard:3.2.1 exterior dimension stone—a general term for a stoneinstalled in a location where temperature, moisture and wind-carried contaminants are regulated solely or primarily by theforces of nature.3.2.2 qualified contractor—a person, persons or organiza-tions having expertise in stone cleaning, proved by docu-mented projects demonstrating successful work, consistency inbusiness or consultancy for a period of five or more years.1This guide is under the jurisdiction of ASTM Committee C18 on DimensionStone and is the direct responsibility of Subcommittee C18.07 on EnvironmentalProperties, Behavior, and Cleaning.Current edition approved Jan. 1, 2014. Published February 2014. Originallyapproved in 2001. Last previous edition approved in 2013 as C1515-13. DOI:10.1520/C1515-14.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at
[email protected] For Annual Book of ASTMStandards volume information, refer to the standard’s Document Summary page onthe ASTM website.Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14. Significance and Use4.1 Exterior dimension stone is chosen for use in contem-porary architecture in part because of its aesthetic appeal.Aesthetics can be significantly diminished when dirt, grime, flyash, algae and other contaminants collect on the surface ofstone.4.2 This guide is intended to assist those who wish topreserve the original appearance of a new structure or to returna stone-clad building to its original color and appearance.4.2.1 Note that cleaning may not be able to return discoloredor faded stone to its original appearance.4.3 This guide may be used as a construction document.5. General Information5.1 Exterior stone is used in honed, textured, or polishedfinishes in many modes in exterior environments. However,trade experience discourages the use of a polished finishmarble or limestone on exterior applications due to suscepti-bility to damage by acids in rain or snow, and by wind-drivendirt particles.5.2 The use of dark colored marbles and limestones forexteriors is discouraged because fading in direct sunlight hasbeen experienced. Discolored or faded stone may not be able tobe returned to its original color by cleaning.5.3 Only marbles with an “A” Soundness Classificationshould be used for exterior installations. An exception istravertine marble (“C” Soundness Classification) which may beinstalled with its natural voids either filled or unfilled. SeeSpecification C503 for soundness classification of marbles.5.4 Stone installed in a mortar bed should be allowed to cureproperly. Do not apply surface treatments to stone set horizon-tally in a mortar bed for at least four weeks followinginstallation.5.5 Carefully identify all wet pedestrian areas withbarricades, “danger” signs or bright red or orange-colored“danger” pylons.5.6 Always test any cleaning method on a sample area todetermine its effectiveness. Always refer to the manufacturer’sinstructions.5.7 When choosing the materials and procedures for clean-ing dimension stone, the most appropriate materials andprocedures should be chosen to promote eco-efficiency andavoid adverse impacts on humans, the structure itself, and theenvironment, see Guide E1971. The alternative cleaningprocesses, cleaning products and their storage, use, anddisposal, equipment choices, and training of personnel in-volved in the work need to be assessed.5.7.1 Certain pertinent questions should be considered here:(1) how is the building used? (2) are there any special cleaningrequirements caused by the type or finish of dimension stoneused? If so, identify the cleaning task and performancerequirements, (3) are there any at-risk human populations toconsider? (4) are there any issues relating to building age orarchitecture? (5) what criteria or measures will be used toevaluate the quality of cleaning and repairs?6. Normal Maintenance6.1 In accessible areas, routinely follow maintenance pro-cedures as specified for Polished Stone, Honed Stone orTextured Finish Stone as applicable. The large expanses ofstone traditionally found on exterior multi-story installationsshould be cleaned as often as necessary to remove accumulatedpollutants.6.1.1 A practice as simple as a hosing down with potablewater on a regular basis will prevent accumulation of dust andacidic deposits left by rain or snow.6.1.2 The cleaning of stone should be done only by qualifiedcontractors who have the craftsmen, equipment, resources, andtechnical expertise to do the work, as well as make any repair,resetting, or repointing that may be necessary.6.1.3 Generally, the processes used in multi-story cleaningwill be similar to normal procedures, except that pumps forpressure wash, or steam and rinse water may be employed toeconomize on the amount of time necessary to the work.6.1.4 Consult material suppliers and qualified contractors toobtain their recommendations for maintenance, materials orrepairs.6.1.5 Always test any cleaning method on a sample area todetermine its effectiveness. Always refer to the manufacturer’sinstructions.6.1.6 Always try the least aggressive cleaning media (po-table water) first.6.1.7 Evaluate project conditions with regard to requiredprotection of adjacent properties and public safety. The protec-tion needed for cleaning multi-story structures will differ fromthat needed for one or two-story buildings.7. Polished Dimension Stone7.1 Polished Stone has a glossy surface that reflects lightand emphasizes the color and markings of the material.7.1.1 Normal maintenance involves only periodic washingwith clean, potable water and neutral (pH7) cleaners. “Soap-less” cleaners are preferred because they minimize streakingand filming. Abrasive cleaners should be avoided.7.1.2 Stone surfaces should first be wetted with clean, hot(not boiling) water. Then, using the cleaner solution (followingmanufacturer’s directions) wash in small, overlapping sweepsfrom top down, or follow manufacturer’s directions if different.Rinse thoroughly with clean, potable water to remove all tracesof soap or cleaner solution. If rinsing is done by hand, changethe water in the rinse pail frequently. Dry with a soft cloth,cotton flannel or chamois, wiping carefully to avoid streaks.The surface may also be allowed to air-dry.7.1.2.1 Warning—Do not use bleach, acid, or strong alkalisolutions on marble or limestone because colors may belightened and the surface etched.7.1.2.2 Select a cleaning agent which suits the nature of thestone.8. Honed Dimension Stone, Normal Maintenance8.1 A honed finish is a satin smooth surface with relativelylittle light reflection.C1515 − 1428.1.1 Normal maintenance of a honed finish involves as-needed washing with clean, potable water and neutral (pH7),mildly abrasive cleaners.8.1.2 Surfaces should be first wetted with hot, clean water.Then, using a mildly abrasive, alkaline cleaner and a mediumnatural bristle brush, wash in overlapping, swirling strokes.Work from top down or follow manufacturer’s directions ifdifferent.8.1.3 Rinse thoroughly then wipe dry with cotton, cottonflannel, or a chamois. Wipe carefully to avoid streaking.Optionally, the stone may be allowed to air-dry.8.1.4 If further cleaning is needed, make a paste to theconsistency of thick syrup by combining a mildly abrasivealkaline cleaning powder and clean, potable water. Apply thepaste uniformly over the surface with a broad brush and allowto stand until dry. Then, use a medium bristle brush withadditional water and scrub vigorously. (More cleaning powdermay be applied at this point.) Rinse thoroughly and dry asdescribed above. Follow manufacturer’s directions.8.1.4.1 See 10.1 and 10.3 for poultice information.8.1.5 Warning—Do not use bleach, acid, or strong alkalisolutions on marble or limestone because colors may belightened and the surface etched.8.1.5.1 Select a cleaning agent which suits the nature of thestone.9. Textured Finish Dimension Stone, Normal Mantenance9.1 Examples of textured finish dimension stone includeThermal Finish Granite, Thermal Finish Limestone, UnfilledTravertine, Rock Face, Split Face, Natural Cleft Slate andNatural Cleft Quartz-Based (Sandstone) Stone.Abrasive, bush-hammered, and sand-blasted finishes are also included in thiscategory.9.1.1 Regular maintenance becomes difficult if dirt is al-lowed to accumulate on the uneven surfaces of these stones. Ifconvenient, textured finished stone may be vacuumed clean.9.1.2 Normal maintenance of textured finish stones involvesas-needed washing with clean, potable water and neutral(pH7), mildly abrasive cleaners.9.1.3 Surfaces should first be wetted with hot, (not boiling)clean water. Then, using a mildly abrasive, alkaline cleaner anda medium bristle brush, wash in overlapping, swirling strokes.Work from top to bottom. Rinse thoroughly with clean water.9.1.4 Warning—Do not use bleach, acid, or strong alkalisolutions on marble or limestone because colors may belightened and the surface etched.9.1.4.1 Select a cleaning agent that suits the nature of thestone.10. The Poultice Method10.1 The Poultice Method is a special cleaning procedurefor removal of deep-seated, time-set dirt and grime. Thepoultice may be applied to honed or textured stone, and isparticularly useful on intricate carvings, moldings and otherdetailing difficult to scrub.10.1.1 The poultice is essentially a strong fluid cleaner,applied by way of a holding medium with a film or membrane,that concentrates its effort over a period of time.10.1.2 The mechanism within this practice relies on theability of the poultice to reliably wick a fluid out from the stonefabric, carrying the staining agent with it. The staining agent iseffectively drawn out backwards on the same path that itentered the stone.10.1.3 The fluid must be capable of dissolving the stainingagent and may be water based or solvent based, depending onthe origin of the stain. The fluid may have additional chemicalsadded to further increase its effectiveness. Water, hydrogenperoxide, acetone, and mineral spirits are commonly usedfluids.10.1.4 Holding mediums are powders such as clays, Fuller’searth, talc, diatomaceous earth, baking soda, and even flour.Cloth or paper products, such as cotton balls, paper towels, andgauze pads can also be used as a holding medium.10.2 The poultice medium is saturated with the fluid, andwhen placed on the stone surface, allows the fluid to penetratethe stone. As the poultice medium starts drying, it has a greateraffinity to draw the fluid than the stone has ability to retain thefluid. This causes the fluid to wick backwards into the poulticemedium, carrying the staining agent with it.10.2.1 A plastic film or membrane is generally required tobe placed over the poultice, which will control the rate ofevaporation. If the fluid is allowed to evaporate too quickly,there may be ample opportunity for it to dissolve the stain priorto evaporation.10.3 Preparation and Application of a Typical Poultice:10.3.1 Mix kaolin or Fuller’s earth with either a commonlaundry bleach or a commercial hair-bleaching solution ofhydrogen peroxide (H2O2) to form a paste the consistency ofpeanut butter or cake icing. (For estimating purposes, figure aconsumption rate of one pound of paste per square foot ofsurface.)10.3.2 Moisten the surface of the stone with the same liquidused to make the paste, wetting beyond the extent of thestained areas.10.3.3 Apply the poultice paste to the stone with a woodenor plasti
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