Cleaning Unpolished White Granite

Technical Procedures Disclaimer

Prior to inclusion in GSA’s library of procedures, documents are reviewed by one or more qualified preservation specialists for general consistency with the Secretary of Interior Standards for rehabilitating historic buildings as understood at the time the procedure is added to the library. All specifications require project-specific editing and professional judgement regarding the applicability of a procedure to a particular building, project or location. References to products and suppliers are to serve as a general guideline and do not constitute a federal endorsement or determination that a product or method is the best or most current alternative, remains available, or is compliant with current environmental regulations and safety standards. The library of procedures is intended to serve as a resource, not a substitute, for specification development by a qualified preservation professional.


We’ve reviewed these procedures for general consistency with federal standards for rehabilitating historic buildings and provide them only as a reference. Specifications should only be applied under the guidance of a qualified preservation professional who can assess the applicability of a procedure to a particular building, project or location. References to products and suppliers serve as general guidelines and do not constitute a federal endorsement nor a determination that a product or method is the best alternative or compliant with current environmental regulations and safety standards.




A. This procedure includes guidance on cleaning unpolished Sierra white
and Milford pink granite. This treatment shall not be used on any polished granite.

B. 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

3. Submittals

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).

C. Materials conservator should review specifications to
ensure they are appropriate.


A. Pressure Readings: Described herein, shall be measured
at the nozzle of the spray apparatus, not at the masonry
surfaces as follows:

1. Low pressure wash shall measure between 100 psi and
400 psi.

2. Medium pressure wash shall measure between 400 psi
and 800 psi.

3. High pressure wash shall measure between 800 psi
and 1200 psi.

B. Construction Engineer: As referred to hereinafter, means
that person or persons representing the Government or
acting for the Governments Contracting Officer.


A. Cleaning operations shall be carried out by a firm with
a minimum of five years specialized experience in the
cleaning of historic architectural masonry.

B. The Contractor shall submit to the Architect written
record of projects for which the Contractor has performed
masonry cleaning of materials the same as those on this

C. The Contractor shall arrange with the Construction
Engineer for a site test of protective methods and
cleaning materials and methods which he proposed to use
to prove that chemical damage to glass, polished stone,
or air conditioning units, painted surfaces,
trees, shrubbery, and grass will not occur.

D. The Contractor shall test all drains which he plans to
use to assure that those drains are functioning properly
before beginning masonry cleaning operation in each area.
The Contractor shall immediately report the location of
drains which are stopped up or blocked to the
Construction Engineer.

E. During cleaning operations, the Contractor shall prevent
solids, such as masonry cleaning residue, from the drains
and drain lines. Drains shall be serviced daily. The
Contractor will be held responsible for cleaning out
drains and drain lines which become blocked or filled as
a result of work performed under this contract.

F. Regulatory Requirements: Comply with municipal and
Federal regulation governing the cleaning, chemical waste
disposal, scaffolding and protection to adjacent

G. Field Samples:

1. The Contractor shall clean 25 square feet
(approximate) sample panels on each type of
masonry. Locations of sample panels to be cleaned
will be selected by the Construction Engineer.

2. Prior to cleaning sample panels, the Contractor
shall submit to the Construction Engineer in
his written description of cleaning methods,
working pressures, materials and equipment
proposed for use in cleaning each type of masonry.
Actual samples of any chemicals shall be submitted
along with letters of certification from
manufacturer that chemical concentrations do not
exceed those specified above.

3. Adjust the chemical concentrations, working
pressures and methodologies during test panel
cleaning, as directed by the Construction Engineer.

4. Sample panels shall be cleaned by the Contractor
using methods, materials, and working pressures
previously submitted and approved. Sample panel
cleaning shall be performed in the presence of the
Construction Engineer. The working pressures
during sample panel cleaning shall be varied up to
the previously submitted and approved capacities to
determine the best working pressure.

5. The Contractor shall obtain the Construction
Engineers written approval of cleaning methods,
working pressures, materials, equipment used and
sample panels before proceeding with building
cleaning operations. For this written approval
purpose, the Contractor shall allow a minimum of
seven calendar days after completion of sample
cleaning to permit the Construction Engineer to
study the sample panels for negative reactions.
Approved sample panels shall be marked and left
unaltered. Approved samples will be used as the
standard for similar work throughout the project.


A. Packing and Shipping: Deliver materials to the site in
the manufacturer's original and unopened containers and
packaging, bearing labels as to the type of material,
brand name and manufacturer's name. Delivered materials
shall be identical to tested materials.

B. Storage and Protection: Store materials off the ground
in a dry, clean location. Remove materials which are
damaged or otherwise not suitable for use from the job


A. Environmental Requirements: No cleaning shall be
executed when air or masonry surface temperature is below
45 degrees F, unless adequate approved means are provided for
maintaining a 45 degrees F temperature of the air and materials
for 48 hours subsequent to cleaning.


A. Perform general cleaning of masonry before the repair and
pointing of the masonry, unless mortar joints are in poor
condition. Serious deterioration could foster excessive
moisture infiltration into the masonry. Perform final
wash down of the masonry no less than 30 days after
masonry repair and pointing is completed.

B. Perform cleaning and washing of the exterior masonry only
during hours of natural daylight.



A. ProSoCo, Inc.

B. Diedrich Technologies, Inc.


A. White Granite Cleaner: Solution of 4% hydrofluoric acid
with a trace of phosphoric acid (less than 0.1%), such as
Sure Klean Restoration Cleaner (ProSoCo, Inc.),
"Diedrich 101 Masonry Restorer Super Concentrate" - diluted 1:4 to achieve
a 4% maximum acid solution (Diedrich Technologies, Inc.),
or approved equal.

B. Warm Water: Potable, non-staining and free of oil,
acids, alkalis, and organic matter, heated to
approximately 180 degrees F.


A. High Pressure Water Equipment: USE CAUTION. Provide
equipment capable of providing water pressure, as
measured at the pump, in the range 25 psi up to 800 psi,
at a temperature of 160 degrees to 180 degrees F. and at
a constant water flow of 4-6 gallons per minute.
Equipment shall have intact, accurate calibrated,
operating gauges to monitor water pressure. See 04510-
04-S and 04510-05-S for usage guidelines and dangers in
using high-pressure cleaning equipment.

B. Spray tips: Fan type, stainless steel, dispersing a 25-50
degree fan spray and a cone shaped spray tip.

C. Brushes: Nylon or Fiber bristle brushes.

D. Protective clothing: Chemicals can cause severe burning
of skin, eyes and lungs. Provide protective clothing
appropriate to the materials and equipment in use.



A. Tests/Inspection: Inspect site conditions and drainage
to determine that cleaning operations can be conducted
without endangering or causing interference with other
materials or work at the site and to determine that
drainage is adequate to safely carry away all waste
material produced during the cleaning operations.


A. Protection:

1. All necessary precautions shall be taken to protect
all parts of the building not being cleaned from
damage during the cleaning process. The Contractor
shall use masking tape where applicable to seal
edges of coverings during masonry cleaning
operations, and remove such coverings when masonry
cleaning operations are completed on that section
of the building.

2. All work shall proceed in an orderly fashion;
working from top to bottom of each scaffold width
and from one end of the elevation to the other.

3. Take all necessary precautions and protective
measures to protect surrounding materials on the
site and surfaces of the building not being
cleaned, from coming in contact with the cleaning
materials and run-off.

4. Fully protect all metals, painted surfaces,
limestone and polished black granite from coming in
contact with acid cleaner.

5. Take necessary precautions to protect workmen and
pedestrians from cleaning chemicals, overspray and

6. Provide protection to prohibit chemicals or run-off
from coming in contact with any painted, polished
or metallic surfaces. Build dams to divert flowing
water to drains in compliance with municipal codes.
Contain or dilute used cleaning materials prior to
disposal in accordance with code.


A. Pre-wet the granite with a low pressure (100-400 psi)
warm water wash.

B. Apply cleaner undiluted to maintain 4% maximum solution
evenly by spraying at 125 psi or with soft fiber bristled
brush. Let solution stand for 3-5 minutes.

C. Rinse granite with clean water at medium pressure (400-
800 psi), removing all cleaner from stone.

D. Reapply cleaner undiluted to maintain 4% maximum solution
and let stand 3-5 minutes.

E. Rinse granite with clean water at medium pressure (400-
800 psi) to remove all acid wash and soil from stone.

F. Stone shall be evenly clean without streaking or

G. Apply cleaner at no more than 4% hydrofluoric acid and
nor more than two times.