Removing Dirt From Stone Masonry Using The Water-Soak Method
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REMOVING DIRT FROM STONE MASONRY USING THE WATER-SOAK METHOD
A. This procedure includes guidance on removing dirt build-up
on masonry using the water-soak method. Prolonged
saturation with water will cause the dirt to expand and
contract at a much faster rate than the stone, causing it
to crack away from the surface.
B. Water washing of stone masonry may be used periodically
to remove dust, dirt, accumulations of grime or airborne
pollutants which settle on the stone and do not get
washed off by the natural action of wind-driven
C. Advantages of the Water-Soak Method:
1. Effective for cleaning heavily deteriorated ornate
masonry that can not withstand pressure washing or
abrasive cleaning techniques.
2. It allows use of mild cleaning agents and
techniques for effective removal of severe carbon
D. Limitations of the Water-Soak Method:
1. EFFECTIVE ONLY ON CALCAREOUS STONE SUCH AS
LIMESTONE--NOT RECOMMENDED FOR CLEANING BRICK,
TERRA COTTA, GRANITE, SANDSTONE, BROWNSTONE AND
MANY OTHER NON CALCAREOUS SURFACES.
2. This is an expensive, time-consuming process. It
is not the most practical method for cleaning an
entire building facade. It is most appropriate for
use on small surface areas.
3. Thorough testing is required. Prolonged exposure
to water may result in oxidation of natural
components of the masonry and may transport
deleterious salts deep into the masonry.
4. Thoroughly saturated masonries may take several
months to dry.
5. Water soaking procedures must be scheduled when
there is no threat of freezing temperatures
throughout the cleaning and drying process.
6. Cascading water used in this process may result in
erosion of the wash surfaces.
7. Scaffolding and rigging requirements for this
procedure are more elaborate.
8. Prolonged exposure to water may result in damage to
interior surfaces, furnishings and equipment.
E. 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. Caution should be provided concerning possible
oxide `blooms' caused by some masonry cleaners,
including the water soak process.
F. 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).
G. See also 04400-02-P and 04400-02-P for alternative
guidance on removing dirt from stone masonry.
A. Clean, potable water (preferably mineral water)
A. Garden hose and nozzle (size appropriate for very fine
B. Fan-shaped spray-tip which disperses water at angle of
not less than 15 degrees.
C. Non-metallic brushes (no iron or brass wire)
D. Wood scrapers
1. Observe all precautions to protect the building
from excess water infiltration and to protect
adjacent property and persons from water over-spray
and run-off damage.
2. Before proceeding with work, check to see that
there are no open joints or cracks and that
windows, doors and other points of entry are
securely covered to prevent entry of water into the
A. Water-soak a test area of approximately 100 SF:
1. Hang or support a 1/2-inch plastic pipe water spray
array under a designated section to thoroughly and
uniformly wet the area, soften any gypsum
encrustation, and prepare it for final rinsing off
with a plain water pressure washing.
2. Connect the spray array to a building water hydrant
with 5/8-inch garden hose as required.
3. Fit the plastic pipe array with four to six fixed
fine spray or mist garden sprinkler heads to cover
the area and wet all face and side surfaces.
4. Provide a mechanical or electric timer control
valve with adjustable time settings, lawn sprinkler
type, with the capability of cycling the spray
water on and off continuously for four hour cycles,
or other timed periods as directed, 24-hours per
B. Following approval of the test installation, operate the
water soak test spray system for a 24 hour period with a
repeat test as directed.
C. Follow the 24 hour water soaking by a plain water
pressure washing (see 04400-01-P for guidance).
1. The Contracting Officer should record the
effectiveness of the cleaning.
2. As Contracting Officer directs, include a repeat
test cleaning on the same area, with a different
timed cycle for sprays, for up to an additional 48
hour period followed by the same pressure wash
rinse and Contracting Officer's observation.
3. The repeat test may be waived by the Contracting
Officer if the initial test results are conclusive.
D. Following approval of the test cleaning, spray the
masonry with a fine mist of water over a prolonged period
of time under the conditions approved by the Contracting
Officer and the RHPO.
1. The spray should never be pointed directly at the
surface. The spray should be fine and use
approximately 110 to 140 liters of water per hour
(45 liters per hour for delicate detailing).
2. Prolonged saturation with water will eventually
loosen any heavy dirt or crusts (it may take from
4-6 hours to a week or more).
3. When the dirt has softened, remove it by hand-scrubbing
with non-metallic brushes or by using a moderate-pressure
water wash (see 04400-01-P); Use a wooden scraper to
remove heavy sulphate crusts.
END OF SECTION