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Review and Evaluation of Selected
Brand Name Materials for Cleaning Gravestones
by Tracy C. Walther- Architectural
Conservator
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.
Efflorescence (salts)
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 monument.
H. Do not assume that a cleaning procedure that is
effective in one specific case is therefore applicable
for all cleaning situations.
I. Consult with a conservation professional.
II. Review and Evaluation of Selected Brand Name
Materials for Cleaning Gravestones
A. Soaps and detergents
1. Soaps (e.g., "Ivory"): commercial household
detergents (liquids and 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," "Naval 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 staining.
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"): Calcium 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 is not 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.
Further detailed information is found in "A Graveyard
Preservation Primer" click here for order information |
