Pencil
Ballpoint Pen
- Paint Remover based on N-methyl-2-pyrrolidone (NMP).
** Organic Solvent such as acetone, lacquer-thinner, orpetroleum-based compound such as dimethyl adipate.
*** Bleach such as calcium hypochlorite.
- N-methyl-2-pyrrolidone (NMP) is mildly toxic and may haveadverse reproductive effects.
Solvents and petroleum-based compounds have toxic vapors, areflammable, and require well-ventilated conditions.
These are suggestions to assist in graffiti removal. Methodsshould always be tested first under the supervision and guidanceof an architectural conservator.
Pencil
Chalk
Paint
Permanent magic marker
Water soluble marker
Ballpoint Pen
Crayon, Lipstick, Shoe Polish
None.
None.
**************************8
-->Tips for Successful Graffiti Removal
- It is important to pre-wet the masonry surface when using an alkaline paint remover; it is also advisable to pre-wet the masonry surrounding a graffitied area to dilute the effect of any cleaning agents that might be inadvertently splashed or spilled on the unsoiled surface. Do not wet the area to be cleaned if the cleaning agent is solvent-based or incompatible with water.
- Always rinse the cleaning agent off the masonry surface starting at the bottom and moving up. This prevents the cleaning agent from running down and staining a lower surface.
- Air temperature can be a factor in graffiti removal. Most paint removers do not work when the air temperature is either very cold or very hot. This may sometimes explain why a method that worked in one instance may not be effective again in another, similar situation.
- Variations within the same type of stone, such as bedding planes, density, finish, or degree of weathering, may explain why some areas of the same stone sometimes clean better that others.
- Even if advance testing has been done and a treatment plan exists, at least some on-the-spot testing will probably be necessary.
- Mortar joints react differently from masonry units, and may require a different cleaning material and/or method to be cleaned effectively.
- Graffiti removal may result in an obviously "clean" spot. Always clean the entire masonry unit that is bounded by mortar joints (but not the joints themselves, unless necessary). The prominence of the clean spot may be minimized by fanning the cleaning out from the spot, and "feathering" it by gradually reducing the strength or thoroughness of the cleaning.
- If it is not possible to completely remove all traces of graffiti without removing some of the masonry surface, it may be preferable to leave the masonry alone. Some graffiti ghosts become less noticeable with time due to fading of the dyes used in paints and markers. Sometimes it may be possible to conceal more obvious graffiti ghosts with carefully-matched paint.
- After graffiti removal, the masonry surface should always be tested with Ph strips to make sure all the cleaning materials have been completely removed. Non-staining Ph strips, available from chemical supply companies, will indicate whether acids or alkalis remain on the masonry surface.
- Although alkaline paint removers are sometimes ineffective on modern formulations of aerosol paints, they can work well in removing multi-layered graffiti because they last longer.
- What removes graffiti in one instance may not always work again even in what appears to be an identical situation.
- More than one cleaning material and technique may be required to clean a heavily graffitied area if different materials were used to make the graffiti. For example, shapes are often outlined with broad-tipped felt markers and then filled in with spray paint.
- Effective graffiti removal often depends on trial-and-error testing, as well as a knowledge of masonry materials, graffiti materials and cleaning techniques.
Acknowledgements
This Preservation Brief was developed under a cooperative agreement between the New York Landmarks Conservancy and the National Park Service. Mark A. Weber, Director, Technical Services Center, served as project coordinator for the Conservancy. The author, Martin E. Weaver, is the Director of the Center for Preservation Research at Columbia University. He is an internationally recognized expert in the conservation of architectural and cultural resources, a noted lecturer, and author of Conserving Buildings: A Guide to Techniques and Materials, as well as numerous articles on the subject.
Anne E. Grimmer, Senior Architectural Historian, Technical Preservation Services, Preservation Assistance Division, National Park Service, coordinated the development of this Preservation Brief and served as Technical Editor. Technical review of this publication by the following is gratefully acknowledged: Frances Gale, Training Coordinator, National Center for Preservation Technology and Training, National Park Service, Natchitoches, LA; Judith M. Jacob, Architectural Conservator, Building Conservation Branch, Northeast Cultural Resources Center, National Park Service, NY, NY; Andrea Mones-O'Hara, Regional Historic Preservation Officer, National Capital Region, General Services Administration, Washington, DC; Nicolas F. Veloz, Conservator of Outdoor Sculpture and Monuments, National Capital Area Office, National Park Service, Washington, DC; and Michael J. Auer, Timothy Buehner, Charles E. Fisher, and especially Kay D. Weeks, Preservation Assistance Division, National Park Service.
Washington, DC. October, 1995
