Identify, Clean & Prevent Lichens on Stone Artifacts, Tombstones, Graves, Walls, Sidewalks InspectAPedia® -
How to clean graves, tombstones, stone walls, sidewalks
How to identify, remove, & prevent algae, lichens, or moss growth on graves, tombstones, stone walls, sidewalks
Photographs of Algae, lichens, moss, mold help identify these substances in nature and on buildings. We provide photos and text to help distinguish among algae, lichens, moss and mold growths on any surface.
Questions & answers about identifying & cleaning or removing lichens or moss from stone surfaces
Lichens on stone surfaces: this article describes and provide photographs and advice on identifying, cleaning, and preventing lichens growth on stone surfaces such as buildings, cultural artifacts, statues, gravestones, sidewalks, stone walls, and pictographs. We include links to references useful in the identification of algae, moss, lichens, and mold.
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We discuss the cleaning/restoration of lichens and moss covered stone surfaces such as building components,cultural artifacts, and grave markers and lichens removal in more detail at Methods for Cleaning Stone Surfaces. Also see Lichens on Roofs for a discussion of lichen damage to shingles and how to prevent lichens growth on roofs.
Colors & Types of Lichens Growth Stone, Marble, Masonry, Tile or Slate Surfaces
Once we include lichens (such as our photo at left, from Portland Maine), the range of colored growths or stains on stone surfaces is quite large. But the most common stain colors are
Black (or dark brown) - most often due to algae, bacteria, dirt or soot, fungus. Fungus may also on occasion produce green or white films on stonework. [Photo of black-brown roof algae on antique metal roof shingles]
Brown or red rust stains - occur on masonry usually due to combination of water and metal components
Below we provide example photographs of different colors and sources of stain or contaminants on stone or masonry surfaces, followed by advice on cleaning and stain prevention.
Reindeer moss: Our second moss and lichens photo (above right, Quetico boundary canoe area, Canada) demonstrates that moss and lichens can coexist happily on the same surface, and even intermixed on a surface where we show two kinds of moss. In our photo, the taller pale growth among the green moss is itself "Reindeer Moss, Caribou Moss" or in other references "Antler Moss".
Our photograph shows Cladonia rangeferina or perhaps Cladonia sp. along with both moss and other lichens on the same stone. Reindeer moss is itself actually a lichen, and is an important food source for reindeer and caribou). Reindeer moss is quite fragile and slow growing, found in both hot and cold climates and in alpine tundra - don't trample it in the wild.
Lichens, one of the most hardy growth organisms found in nature, can grow in harsh conditions. Moss and lichens are both more than a cosmetic issue on most materials.
By holding moisture against the stone or other material surface lichens but more so moss speed the wear of the surface in freezing climates by increasing frost damage to the surface and by action of the organism's "roots" that penetrate the material surface.
Our photo (left) shows green lichens growth on a gravestone near Vassar College, in Poughkeepsie, NY. Notice that the lichens appears first on the more roughened stone surfaces inside the carved gravestone lettering, and on the rough-cut north face of the stone.
In addition to stone surfaces and mineral-covered roof surfaces, lichens also grows just fine on clay tile roofing and on wood (as those photo links show).
The lichens shown on the stone monument (above left), and the flat black stone (above right), demonstrate that this organism is happy in an enormous range of climates, from high elevation hot dry southern areas (Las Cabras, Guanajuato, Mexico, at about 7000' elevation) to arctic tundra (above right, elevation 50', in Northern Norway near Kirkenes [(Finnish: Kirkkoniemi, Sámi: Girkonjárga) the centre of the municipality of Sør-Varanger in Finnmark county, Norway], well above the arctic circle, courtesy Jennifer Church).
White Lichens photos: White & Pale Gray Lichens photos: The importance of lichens as an organism that can attack cultural artifacts is demonstrated by our photo (left) of lichens surrounding a pictograph from the Quetico boundary waters canoe area in Canada. Also see our pale lichens photos just above in this article. Also see these photos of gray-green roof lichens and gray roof lichens.
For more about conservation of stone artifacts such as this pictograph, consult "Microbial Communities in Caves: Ecology, Physiology, and Effects on Paleolithic Paintings" found in Art, Biology, and Conservation: Biodeterioration in Works of Art, Robert J. Koestler et als. Eds., Metropolitan Museum of Art, 2003, ISBN 1-58839-107-8, p. 210-225.
Green Lichens photos: See Green Stains on Stone for additional green lichens pictures - our photo of "Reindeer Moss, Caribou Moss" or in other references "Antler Moss". Our photograph shows Cladonia rangeferina or perhaps Cladonia sp. along with both moss and other lichens on the same stone.
Yellow Lichens photos: see Colors & Stains on Stone for our photo of yellow-orange lichens on stone.
Lichens on Roofs demonstrate the mechanical damage that can be caused by lichens on surfaces. See Lichens on Roofs for details about the causes, effects, and prevention of lichens growth on roofing surfaces.
Lichens is often found growing on roof shingles, especially asphalt and wood shingles as we show here where we demonstrate the damage to the surface when lichens is removed. Our photos (below) illustrate how serious lichens damage can be to a mineral surface.
Does Lichens Always Need to be Cleaned Off of Stone Surfaces?
No, of course not. The lichens growing on this stone wall in Poughkeepsie, NY (constructed by and found at Adams Fairacre Farms) is not going to do any harm, and in fact adds to the attractiveness of the wall.
Online Guide to Types of Stains on Building Surfaces:
In the following guide we list types of stains by stain color & appearance, by building location or material, and by stain cause. We distinguish among the following stuff that may stain or be found growing building roofs, walls, or other surfaces, with extra focus on asphalt shingle roofs as well as other roofing materials such as wood shingles, wood shakes, roll roofing, and even slate or tile roofs. Some of these types of roof stains or discoloration are only cosmetic in nature, while others may indicate growths that are likely to reduce the roof covering life. A more detailed, illustrated version of the list below is given at STAIN DIAGNOSIS on BUILDING EXTERIORS.
Black stains on asphalt roofing products such as asphalt shingles or roll roofing, caused by extractive bleeding (product defects) - see Bleed-Through and see Roofing material defect / environmentally-caused roof shingle stains.
Black, brown, or gray stains on roofing products due to debris left on the roof surface, such as piles of leaves and organic waste from nearby trees. See Debris Staining and see Proximate cause roof shingle stains
Black or other colored stains on roof surfaces may be caused by soot from chimneys, both wood-fired and oil-fired devices. Black or other colored stains may also appear on roof surfaces from nearby industrial activities. See Soot Staining.
Brown or red stains on roof surfaces are often caused by rust from wearing steel flashing or other on-roof metal products. See Rust Stains on Shingles.
Green roof stains on roof shingles, clay tiles, cement tiles, and asbestos cement roof shingles or newer fiber cement roof shingles are often caused by algae. For details see ALGAE STAINS ON ASPHALT ROOF SHINGLES. Moss on roofs is also often green and should be unmistakable in appearance. See ALGAE, FUNGUS, LICHENS, MOSS on SHINGLES.
Moss on roofs and other building surfaces: see ALGAE, FUNGUS, LICHENS, MOSS on SHINGLES, and Green Stains on Stone. Green or other colored mosses are a bit easier to remove than lichens on roofing surfaces, but both can carry away mineral granules and damage the roof surface. Moss tends to hold more water and moisture on the roof surface. So in our opinion moss is more likely to damage a roof surface than lichens or algae. Also see ALGAE, FUNGUS, LICHENS, MOSS COMPARED.
Rust Stains on buildings - see Rust Staining - Red or Brown Rust Stains (on shingles)
Soot or Creosote black or brown stains on roof surfaces near or below chimneys - see SOOT STAINING - Black Soot Stains on Roof Shingles Around Chimneys and see Proximate cause roof shingle stains
Stains on stone or masonry surfaces - see STONE CLEANING METHODS for cause, cure, and prevention
White stains on roof surfaces may be from wash-down of pigments in paint on surfaces above the roof such as a gable end or dormer wall; white or less-black roof surfaces may also be found below copper or aluminum flashing whose salts run down the roof surface in wet weather, preventing algae or moss growth and leaving a white area on an otherwise stained roof surface. Our article at ALGAE, FUNGUS, LICHENS, MOSS on SHINGLES includes a photograph of this condition on a wood shingle roof.
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Guides to identifying mosses, lichens, algae Graphic Guide Ontario Mosses (some of which appear widely dispersed by climate and geographic area, not just in Ontario) which offers a graphic guide to mosses. worldofmosses.com/ggom/index.html
Also see the sources listed at worldofmosses.com/ggom/ggomBibliography.html
Also see the Journal Folia Geobotanica, Springer, Netherlands ISSN1211-9520 (Print) 1874-9348 (Online) IssueVolume 11, Number 2 / June, 1976 DOI10.1007/BF02854759 Pages217-22
The Ecology of Algae, F.E. Round, Cambridge University Press, 1984 ISBN-10: 0521269067 ISBN-13: 978-0521269063 (Available at Amazon.com) After an introduction outlining the chemical and physical characteristics of the environment, the book goes on to look at the actual habitats in which algae occur. The communities of the individual habitats such as open water, sediments, rocky shores, coral reefs, hot springs, sea ice, soil, etc., are then discussed with special phenomena highlighted, for example rhythmic activity, nitrogen fixation and buoyancy. There are also chapters on seasonal cycles of algal growth, energy flow, geographical dispersion, palaeo-ecology and contribution to sediments. The importance of algae in symbiotic relationships and their considerable significance to animal grazers in aquatic food chains are also discussed. The final chapter deals with the relationships of algae to eutrophication and pollution of water. This is an important aspect, which can only be understood through an appreciation of algal ecology.
Lichens of North America, Irwin M. Brodo, Yale University Press, 2001, ISBN-10: 0300082495, # ISBN-13: 978-0300082494 (Available at Amazon.com)
Quoting from Library Journal: Lichens are a combination of a fungus and an alga but have a unique structure and appearance quite different from either. Existing worldwide and growing on a variety of surfaces, including rocks, soil, and trees, they may appear leafy, shrubby, mossy, crusty, or jellylike and are seen in a wide range of colors, from brilliant oranges, yellows, and reds to dull grays and browns. This huge new book, written by a world authority on lichens and emeritus research scientist at the Canadian Museum of Nature, Ottawa, provides information on about 1500 of the roughly 3600 recognized North American lichens. Part 1 introduces lichens in 14 clearly written chapters that discuss their biology, ecology, geography, environmental roles, and collection. Part 2, the heart of the book, is a guide that offers identification keys to groups, genera, and species and their descriptions, with accompanying photographs and North American distribution maps. The more than 900 truly beautiful, full-color photos were taken by the Sharnoffs, nature photographers whose work has been widely published in National Geographic, Smithsonian, and elsewhere. Of value to professionals and amateurs alike, this book is certain to be a classic reference for decades to come. Highly recommended for academic and research libraries and for public libraries where interest warrants; libraries needing only a brief yet informative introduction to lichens should consider William Purvis's inexpensive Lichens (Smithsonian Institution, 2000). William H. Wiese, Iowa State Univ. Lib., Ames
Cultural Heritage and Aerobiology, Methods and Measurement Techniques for Biodeterioration Monitoring, Paolo Mandrioli, Guilia Caneva, and Cristina Sabbioni, Eds., Kluwer Academic Publishers, 2003 ISBN 1-4020-1622-0 See our book review of this reference. The conservation of art objects relies on expert inspection, testing, and diagnosis of environmental contaminants and factors that affect the deterioration of artworks, such as mold, moisture, temperature, acid rain, and both indoor and outdoor air quality components. This text reviews these important art conservation concerns and describes methods for the inspection, testing, and monitoring of environmental conditions wherever artworks and other cultural artifacts are located.
Thanks to Patrick Walsh for discussing cleaning methods for gravestones & tombs May 2010
Shingle Shield™ are zinc strips that are inserted under the shingle tabs of individual shingles to reduce moss, lichens, and algae growth on asphalt roofing - see shingleshield.com
StainhandleR are zinc strips that are inserted under the shingle tabs of individual shingles to reduce moss, lichens, and algae growth on asphalt roofing- see stainhandler.com
Zinc-Shield® - zincshield.com and Z-stop™ zinc roofing strips - z-stop.com, are roll-out zinc strips intended for installation near the ridge of a roof to reduce moss, lichens, and algae growth on roofs
04/09: thanks to William M. Norman, P.E., S.E., Keeler-Webb Associates, 486 Gradle Drive, Carmel, IN 46032 for opening discussion regarding the legitimacy of extractive bleeding as a term to apply to asphalt roofing material. Mr. Norman suggests that many (not all) black stains on asphalt roofing may be due to algal growth. We will report progress in this discussion as updates to this web article.
How to Recognize & Control Sooty Molds, USDA publication on the recognition and control of black sooty molds, including on buildings.
This publication is also available in printed form from the U.S. Government Printing Office, 1992 657-152 HT-69 1992. The original article was authored by Kenneth K.Kessler, Jr., Principal Plant Pathologist, U.S. Forest Service, in the Department of Agriculture of the United States. Copies are also available from North Central Distribution Center, Forest Products Laboratory, One Gifford Pinchot Dr., Madison WI 53705-2398.
"Microbes Eating Away at Pieces of History", Vina Venkataraman, The New York Times, 27 June 2008 p. F3.
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
Paint and Surface Coatings, Theory and Practice [purchase at Amazon.com], R. Lambourne & T.A. Strivens, Ed., Woodhead Publishing Ltd., William Andrew Publishing, 1999 ISBN 1-85573-348 X & 1-884207-73-1 [This is perhaps the leading reference on modern paints and coatings, but is a difficult text to obtain, and is a bit short on field investigation methods - DF]
Analysis of Modern Paints, Thomas J.S. Learner, Research in Conservation, 2004 ISBN 0-89236-779-2 [Chemistry of modern paints, overview of analytical methods, pyrolysis-gas chromatography signatures of basic modern paints and their constituents, Fourier transform infrared spectroscopy for paint analysis, direct temperature-resolved mass spectrometry, and analysis in practice - technical reference useful for forensic paint science, focused on art works -DF]
Seeing Through Paintings, Physical Examination in Art Historical Studies, Andrea Kirsh, Rustin S. Levenson, Materials in Fine Arts, 2000 ISBN 99-051835 [ forensic science, technical reference, focused on art works - DF]
Sealants, Durability of Building Sealants (RILEM Proceedings), J.C. Beech, A.T. Wolf, Spon Press; illustrated edition (1995), ISBN-10: 0419210709, ISBN-13: 978-0419210702 This book presents the papers given at the RILEM Seminar held at the Building Research Establishment, Garston, UK in October 1994. The book provides an opportunity for researchers to review up-to-date progress towards the achievement of the objectives of the standardisation of laboratory techniques of sealants in the variety of service conditions to which they are exposed.
Soiling and Cleaning of Building Facades (RILEM Report), L.G.W. Verhoef (Editor), Routledge; 1 edition (November 3, 1988), ISBN-10: 0412306700, USBN-13: 978-0412306709 The report of a comprehensive investigation by RILEM which examines all aspects of the cleaning of facades, subject to soiling by both biological and non-biological agencies. The contributors are international authorities working in this field giving essential advice to all those who need to know how to approach the problems connected with the soiling and cleaning of building facades.
Staining, Prevention of Premature Staining in New buildings, Phil Parnham, Taylor & Francis; 1996, ISBN-10: 0419171304, ISBN-13: 978-0419171300 The appearance of ugly staining early in a buildings life, ruins an otherwise pleasing appearance, tarnishes the image of the owners and gives rise to costly refurbishment works. In this book Phil Parnham raises a number of questions that should be considered whenever a new building is being designed or built. These are: * why has staining become so prominent; * what causes premature staining; which parts of new buildings are likely to be affected; * how can it be avoided? By using a number of highly illustrated case studies, the author answers these questions and ends by suggesting measures that should be taken by all design and construction professionals to prevent premature staining.
Paint Handbook: testing, selection, application, troubleshooting, surface preparation, etc., Guy E. Weismantel, Ed., McGraw Hill Book Company, 1981, ISBN-10: 0070690618, ISBN-13: 978-0070690615, [Excellent but a bit obsolete paint theory and practice, also a bit light on field investigation methods, out of print, available used-DF] How to select and apply the right paint or coating for any surface. The first major reference to help you choose the correct paint or other finish to do the job best on a particular surface exposed to a particular environment. Experts in the field give full advice on testing surface preparation, application, corrosion prevention, and troubleshooting. The handbook covers wood, metal, composites, and masonry, as well as marine applications and roof coatings. A ``must'' working tool for contractors, architects, engineers, specification writers, and paint dealers.
Paint and Surface Coatings, Theory and Practice, R. Lambourne & T.A. Strivens, Ed., Woodhead Publishing Ltd., William Andrew Publishing, 1999 ISBN 1-85573-348 X & 1-884207-73-1 [This is perhaps the leading reference on modern paints and coatings, but is a difficult text to obtain, and is a bit short on field investigation methods - DF] Provides a comprehensive reference source for all those in the paint industry, paint manufacturers and raw materials suppliers, undergraduate and postgraduate students, and industrial paint users. R. Lambourne was in the Research Department at ICI Paints Division and the Industrial Colloid Advisory Group, Birstol University, UK.
Understanding Ventilation, John Bower, The Healthy House Institute, ISBN 0-9637156-5-8, 1995 [General building science-DF - ** Particularly useful text. Mr. Bower has retired from the field but his book continues to be important]
"Moisture Control in buildings: Putting Building Science in Green Building," Alex Wilson, Environmental Building News, Vol. 12. No. 5. [Good tutorial, "Moisture 101" outlining the physics of moisture movement in buildings and a good but incomplete list of general suggestions for moisture control - inadequate attention given to exterior conditions such as roof and surface drainage defects which are among the most-common sources of building moisture and water entry.--DJF]
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