Removing Dirt From Limestone Ornament Using A Hot Lime Poultice
- Procedure code:
- Developed For Hspg (Nps - Sero)
- Last Modified:
REMOVING DIRT FROM LIMESTONE ORNAMENT USING A HOT LIME POULTICE
THE CLEANING OR REMOVAL OF STAINS FROM STONE MAY INVOLVE THE USE
OF LIQUIDS, DETERGENTS OR SOLVENTS WHICH MAY RUN OFF ON ADJACENT
MATERIAL, DISCOLOR THE STONE OR DRIVE THE STAINS DEEPER INTO POROUS
STONES. USE THE PRODUCTS AND TECHNIQUES DESCRIBED HERE ONLY FOR
THE COMBINATIONS OF DIRT/STAIN AND STONE SPECIFIED.
A. This procedure includes guidance on cleaning dirt from
limestone using a hot lime poultice - also known as
Baker's Lime Method. Developed by Robert Baker in the
1950's, THIS METHOD OF DIRT REMOVAL IS LABOR INTENSIVE
AND, THEREFORE, IS BEST USED ON HIGHLY SIGNIFICANT
1. Baker's Lime Method is a 4-stage process which
includes cleaning, repair, consolidating and
2. This procedure describes the cleaning stage. Other
stages in the process are described in 04460-02-R.
B. Dirt may consist of particles of dust, sand or grit, or
tarry soot. Particulate dirt or soiling may result from
vehicular or human traffic or from pollutant or sulfate
crusts building up in protected areas not regularly
washed by rain. Pollutant crusts hasten masonry
dissolution and should be removed.
C. Safety Precautions: Check manufacturer's literature for
precautions and effects of products and procedures on
adjacent building materials, components, and especially
vegetation. Take appropriate protective measures.
D. 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).
E. For general information on the characteristics, uses and
problems associated with limestone, see 04460-01-S.
A. Lime putty
B. Burlap or cheesecloth
C. Plastic sheeting
E. Clean potable water
A. Hand spray bottle
B. Dental picks
C. Small, soft bristle brushes
D. Trowels and spatulas
A. Thoroughly wet the stone with clean water.
B. Using a trowel, press lime putty into the affected
C. After a thick coat has been applied, bind it with wet
burlap or cheesecloth; Secure it with string.
D. Loosely tie a heavy-duty polyethylene sheet around the
E. Keep the ornament covered for about 2-3 weeks.
F. Periodically, lift the sacking during that time and spray
the poultice with water to keep the poultice damp.
G. Carefully lift off the lime in small portions using
spatulas or small trowels (use water sprays to help
loosen the poultice).
H. Much of the dirt will not immediately detach with the
poultice material; The poultice moistens the dirt so that
it can be removed more easily by washing and brushing.
I. Using hand sprays, dental picks, small tooth brushes or
stencil brushes, gently remove loosened dirt left on the
J. If, after cleaning, there is any evidence of stone
damage, attempt limestone surface repair using
consolidation and lime mortar (see 04460-02-R).
END OF SECTION