Removing Dirt From Stone Masonry By Steam Cleaning
- Procedure code:
- Developed For Hspg (Nps - Sero)
- Last Modified:
REMOVING DIRT FROM STONE MASONRY BY STEAM CLEANING
A. This procedure includes guidance on removing dirt
build-up on stone masonry by steam cleaning.
B. Advantages of Steam Cleaning:
1. Is effective in cleaning heavily deteriorated
ornate masonry that can not withstand pressure
washing or abrasive cleaning techniques.
2. Allows use of the mildest possible cleaning agents
and rinsing pressures for removal of severe carbon
encrustations on calcareous surfaces.
3. Effective in removing organic growth from the
4. There is less of a chance of staining as compared
to other cleaning methods.
C. Limitations of Steam Cleaning:
1. This method is more expensive (due to the high cost
of steam-generating equipment) and requires more
time than other methods.
2. Excessively high temperatures with this procedure
is a safety hazard to the operators.
3. It is sometimes difficult for the operator to
monitor his progress due to the cloud of steam
generated with this technique.
4. This method is NOT effective in removing severe
D. Safety Precautions:
1. Precautions should be taken to guard against
unnecessary water infiltration. Monitors should be
set within the walls to determine moisture content
and possible problems.
2. Soft water should NOT be used on carbonate stone.
Soft water sometimes contains minerals that can
bring out impurities in the stone resulting in
permanent discoloration. Mildly acidic water can
also cause carbonate stone to become more soluble
resulting in the eventual dissolution of the stone.
E. See 01100-07-S for general project guidelines to be
reviewed along with this procedure. These guidelines
cover the following sections:
1. Safety Precautions
2. Historic Structures Precautions
4. Quality Assurance
5. Delivery, Storage and Handling
6. Project/Site Conditions
7. Sequencing and Scheduling
8. General Protection (Surface and Surrounding)
These guidelines should be reviewed prior to performing
this procedure and should be followed, when applicable,
along with recommendations from the Regional Historic
Preservation Officer (RHPO).
F. See also 04400-01-P and 04400-03-P for alternative
guidance on removing dirt from stone masonry.
A. Dow Chemical
B. Union Carbide Corporation
C. Ashland Chemical
A. Non-ionic detergent such as "Tergitol,
"Triton, "Igepal", or approved equal.
1. Use dilution as approved by testing on material to
2. Acidic or alkaline products are NOT acceptable.
B. Clean, potable water (preferably mineral water)
A. Garden hose and nozzle (approximately 1/2" diameter)
B. Non-metallic brushes (no iron or brass wire)
C. Wood scrapers
D. Flash boiler for generating the steam
1. Cleaning methods should be tested prior to
selecting the one for use on the building; The
simplest and least aggressive methods should be
2. The level of cleanliness desired should be
determined; A new appearance look is both
inappropriate and requires an overly harsh cleaning
3. Prolonged exposure of water causes rapid
deterioration in older structures.
4. Take precautions to ensure that the water does not
penetrate the surface and cause damage to the
interior of the structure.
5. This procedure may cause corrosion of hidden iron
work and steel anchors causing either staining or
cracking due to the rapid expansion of the metal.
6. If the masonry remains saturated during the first
frost, surface pieces may spall off as the water
7. Iron and chloride in the water can cause
disfigurement and staining.
B. Surface Preparation:
1. Fill the buckets, usually one or two, with about
two gallons of water.
2. Beginning at the top and gradually working down,
scrub lightly with the fiber brush to remove any
superficial deposits. Take care to avoid scratching
or otherwise damaging any polished surfaces.
3. Rinse with clear water.
4. Dry with clean, lint-free toweling or rags.
5. Tenacious mineral deposits may be treated locally
with gentle abrasion using wooden paddles or
sticks. Great care should be exercised to avoid
damaging the highly polished surfaces of masonry
where they exist.
A. Direct steam (generated in a flash boiler) against the
masonry surface. The heat of the steam will swell and
soften dirt deposits and loosen them from the masonry
1. Use a very low-pressure nozzle (10-30 psi)- about
1/2 inch diameter aperture.
2. Hold the nozzle tip consistently a minimum of 12
inches from the masonry surface.
B. Remove softened dirt by hand, scrubbing with non-metallic
brushes. Use a wooden scraper to remove heavy sulphate
C. Rinse thoroughly with water until surface tests as neutral as
indicated with pH strip.
D. If steam alone is not effective, it may be supplemented
with a non-ionic detergent.
END OF SECTION