I. INTRODUCTION -- Some important general guidelines to remember when
considering cleaning burial monuments:
A. Evaluate the general condition of the burial monument. Do not attempt to
clean the monument if it exhibits any cracks, flaking and scaling, or eroding
granular surfaces. Carefully sound (gently tap surface with finger) stone to
determine if there are any underlying hollow areas. If hollow areas are
detected, do not continue with cleaning or handling.
B. Determine the type of soiling to remove it in the most effective manner.
Types of soiling could be:
Carbonaceous or sooty soiling
Urban grime; dirt
Organic--algae, fungi, lichens, mosses
Stains--metallic, oils, etc.
C. Initiate cleaning process with the least aggressive method--gentle, clean
water rinsing. If washing with water alone is not sufficient, carefully
proceed with the use of a selected material to facilitate cleaning. Select
the gentlest possible method that will achieve a desirable or acceptable
level of cleanliness.
D. Always test selected cleaning method(s) before general application. Test
entire cleaning procedure in a small inconspicuous area on the monument.
E. Pre-wet monument with water before the application of any chemical
cleaning solutions. Pre-wetting prevents excessive penetration of cleaning
solutions and soiling into the stone, and facilitates softening of soiling.
F. Clean from the bottom to the top of the monument to avoid streak staining
on the stone. Periodically rinse runoff.
G. Always rinse thoroughly with water. Residues from chemical cleaning
solutions can create a blotchy appearance, provide mediums for bacterial
action, and cause staining. Do not allow cleaning solutions to dry on a
H. Do not assume that a cleaning procedure that is effective in one specific
case is therefore applicable for all cleaning situations. professional.
I. Consult with a conservation
II. Review and Evaluation of Selected Brand Name Materials for Cleaning
A. Soaps and detergents
1. Soaps (e.g., "Ivory"): commercial household detergents (liquids
powders) are not recommended for cleaning masonry. They are rendered
insoluble by calcium ions present in stone and hard water. They may also
produce free alkali and fatty acid salts.
2. Non-ionic Detergents (e.g., Photo Flo - a Kodak product): Non-ionic
detergents are recommended for cleaning gravestones. They are electrically
neutral cleaning agents that do not contain or contribute to the formation of
soluble salts. They provide better wetting of the masonry surface and,
therefore, successfully facilitate the removal of general soiling. Non-ionic
detergents are available from conservation, janitorial, and photographic
suppliers. A suggested cleaning solution is one ounce non-ionic detergent to
5 gallons water.
B. Acidic Cleaning Materials
1. Hydrochloric or Muriatic Acid, Phosphoric Acid (e.g. "Lime Away,"
Jelly"), oxalic acid are not recommended for general cleaning of gravestones.
The use of hydrochloric or muriatic acid may result in ferrous chloride
(rust) staining and the deposition of soluble salts. Muriatic acid, which is
readily available in hardware stores, is a raw acid. It is a by-product of
processing steel and contains metallic particles that can cause ferrous
C. Alkaline, Corrosive, and Biocidal Cleaning Materials
1. Sodium Hydroxide (e.g., "Borax"), Sodium Hypochlorite (e.g., "Clorox"
"liquid chlorine") is not recommended for general cleaning of stone.
2. Calcium Hypochlorite (e.g., Chlorine, "HTH," "Shock Treatment"):
hypochlorite or chlorine is effective for the removal of biological growth.
It is a granular product that is not to be confused with "liquid chlorine" or
sodium hypochlorite. Calcium hypochlorite is available from swimming pool
suppliers. A suggested cleaning solution is one ounce calcium hypochlorite to
one gallon hot water. This product should be used only when a waterhose with
a good water pressure (e.g., 55 psi) is available.
3. Ammonium Hydroxide (e.g., household ammonia): Solutions of household
ammonia are recommended for cleaning light colored stones. Ammonia is
particularly effective for the removal of biological growth. One cup ammonia
to one gallon water.
4. Quatemary Ammoniums (e.g., algaecides or biocides for swimming pools):
Quaternary Ammoniums have a slightly different chemical structure than
ammonium hydroxide. They are especially effective for the removal of
biological growth, particularly stubborn black algae. Quaternary ammoniums
are available from swimming pool suppliers and list ingredients such as
alkylbenzyl trimethyl ammonium, benzyl alkyl dimethyl ammonium chlorides, or
benzyl aklyl dimethyl ammonium bromides.
5. Trisodium Phosphate (e.g., "TSP, "Calgon"): Trisodium phosphate
recommended for cleaning monuments. It can cause the formation and deposition
of soluble salts. "Calgon" contains trisodium phosphate and a number of
additives that may be detrimental to monuments.
6. "Fantastic" All Purpose Cleaner, "Formula 409," "Spic
and Span" and
abrasive cleansers: These are not recommended for cleaning monuments. Avoid
products containing sodium chloride, sodium sulfate, sodium carbonate, sodium
bicarbonate, and ammonium carbonate, due to their ability to form and deposit
soluble salts in monuments.
III. MISCELLANEOUS MATERIALS OR TOOLS
A. The following items are recommended for use in cleaning procedures for
masonry: soft natural bristle (e.g., tampico) brushes, nylon brushes, tooth
brushes, Q-tips, sponges (especially natural sponges). Wood and some plastic
spatulas are also recommended.
B. Do not use metal brushes or scrapers, or abrasive pads (e.g., "Brillo,"
"Scotchbrite") to clean monuments.
IV. SOME FINAL REMINDERS ABOUT BRAND NAME CLEANING MATERIALS
A. Do not rely solely upon product labels or advertising. Brand name
materials that are readily available from hardware and grocery stores are
generally intended for household use. Information is not provided for
specialized applications outside of the home or workshop.
B. Remember to consult with a conservation consultant before cleaning. The
use of improper cleaning materials and practices can cause serious and
irreparable damage to gravestones.
Tools and Materials for Gravestone Cleaning Projects
by Fannin Lehner Preservation Consultants
Marble and Limestone
Non-ionic Detergent (Photo-Flo-Kodak product)
Household Ammonia (Requires water hose for rinsing and Hydrion Paper test
strips for pH testing.)
Calcium Hypochlorite (HTH) for biological growth retardation. (Requires water
hose for rinsing and Hydrion Paper test strips for pH testing.)
Slate and Other Stone
Non-ionic Detergent (Photo-Flo-Kodak product)
Good water supply
Non-ionic Detergent (Photo-Flo--Kodak product).
1/4 oz./5quarts water
Ammonia--1 cup/1gal. water (for marble only)
Calcium Hypochlorite (granular)-2 oz.dry/1 gal. warm water
Assortment of brushes (NOT WIRE) of varyimg stiffness.
Toothbrushes (firm), sponges
Scrapers- craft sticks, plastic scrapers
Kaolin/porcelain clay (dry),
Glycerine (use 50/50 mixture with water)
Saran Wrap and heavy plastic for wrapping
Tape/ string to secure plastic
Scrapers- plastic and wood
Wire brushes, metal instruments, abrasive pads (Scotchbrite, Brillo, Steel
Acid or acidic cleaners (especially on marble or limestone!) (Should only be
used by conservators with proper training on non-calcareous stone)
Household cleaners: soap (Ivory), detergents (liquid or powder), Borax,
Clorox, TSP, Calgon, Fantastik, Formula 409, Spic and Span (or any other
REMEMBER: The use of improper cleaning materials and practices can cause
serious and irreparable damage to gravestones! Make sure the stone is stable
before attempting to clean it - no flaking, delaminating, etc.