Stone Maintenance
Guide
|
|
Stone Types | Considerations
| Environment | Preventive
Maintenance |
| Preservation | Restoration
| |
This
report is a short summary and general guide of maintenance
recommendations and processes which have proved practical
for many stone surfaces over the years. It should not be assumed
that any particular process description or recommendation
is suitable for any particular project or situation without
qualification. There are many variables which must be considered
when designing a maintenance program including: physical properties
of the stone, abrasion risk, hostile factors in the environment,
the maintenance budget and the skill of the maintenance personnel.
It is highly recommended that a maintenance professional be
consulted if there is any doubt about whether or not a specific
method or product is safe and effective. A
complete Maintenance Guide for stone, grout, and tile care
for Marble tile, Grout, Granite tile, Corian, ceramic
tile, Granite Countertops, Marble Countertops,
slate, limestone, travertine, sandstone, Ceramic Floor Tile.
|
Stone
Types |
Marble
Composition:
Calcite, Calcium Carbonate
Hardness: Soft
Absorption: Oil, Water
Limitations: Absorbs
oils and other liquids, easily scratched, acid sensitive
Sealer: Penetrating type siloxane or fluoropolymer
Cleaner: Natural Soap or Neutral pH detergent
Finish: Polished - liquid Paste wax ; others:
none
Notes: Polished marble is ideal for vertical
application but requires a high level of maintenance when used
as flooring especially in high traffic situations. Non-reflective
finishes perform well as flooring with minimal maintenance once
treated with recommended sealers. Kitchen use should be carefully
evaluated due to oil absorption.
|
Limestone
Composition:
Calcite, Calcium Carbonate
Hardness : Soft
Absorption : Oil, Water
Limitations : Absorbs oils and other liquids,
easily scratched, acid sensitive, polished-interior use only
Sealer : Penetrating type siloxane/fluoropolymer
Cleaner: Natural Soap or Neutral pH detergent
Finish: Polished - liquid Paste wax ; others:
none
Notes: Most true limestone types are porous and
absorbent. Some limestone is semi-metamorphic and will have
physical properties similar to metamorphic marble. If the limestone
is metamorphic it is "Marble". For our purposes here, LIMESTONE
is the chalky porous type typical of most French and Spanish
limestone. Non-reflective finishes are practical as flooring
but require sealing to minimize stains. Dense, low absorbent
varieties of limestone can be suitable in shower areas but beware
of using too soft a limestone in high stress areas. Sealing
is normally recommended for both interior and exterior locations.
|
Granite
Composition:
Quartz, Feldspar (varies)
Hardness : Hard
Absorption : Varies - Oil, Water
Limitations : Absorbs oils and other liquids,
brittle
Sealer : Sub-surface repellents - oil repellent
type recommended
Cleaner: Neutral pH detergent or pure soap
Finish: None Normally - Wax OK
Notes: Granite is typical for kitchen counter
use. Sealing is recommended for most stones. Granite is the
hardest of the polished stones commercially available and is
used in high stress situations. Polished granite usually is
more absorbent to liquids than many people suppose. Flamed granite
surfaces are very absorbent due to the stress fractures in the
stone caused by the flaming process and should be sealed if
it is desired to maintain the original color and appearance
of the stone over time.
|
Slate
Composition:
Muscovite Chlorite (wide variation in composition)
Hardness : Soft - easily scratched
Absorption : Low - medium oil, water other
liquids
Limitations : Absorbs oils/ liquids, cleft
planes can spall
Sealer : Sub-surface repellents oil repellent
type recommended
Cleaner: Neutral pH detergent or pure soap
Finish: Acrylic OK - wax OK
Notes: Cleft slate is very durable in most situations
but quality varies. Slate is typically rustic in appearance
but some milled or smooth products are available in some varieties.
Wear is typically taken on the peaks or high spots of the textured
surface. Acrylics are used when a highly reflective finish is
desired. Excellent exterior paving stone. Higher absorbency
varieties may not be suitable for exterior areas in freezing
climates.
Slate characteristics vary with source. Domestic is typically
black, green or mottled (Pennsylvania) and is relatively dense.
Many imported slates are available today with wide ranging physical
characteristics and overall suitability. Evaluate your stone
for density, tensile strength, absorbency and abrasion resistance.
Make sure your slate characteristics are compatible with the
intended function. ÿÿ
|
Considerations |
Surface
Textures
Heavy
Textures
Split face: Rough surface texture, ed rustic
Saw-cut: Rough saw finish, saw marks visible
Flamed: Damp stone spalled by acetylene torch
Sandblasted: Pitted, roughness depends upon
grit used
Smooth Textures
Honed: Smooth to the touch but not reflective
Polished: Mirror finish, (abrasive process)
Notes: Heavy Textures are most utilized for rustic
design needs and for slip resistance. Most will benefit from
treatment with repellents
Honed flooring surfaces do not show wear damage as dramatically
as polished surfaces do and therefore are more economically
maintained than polished surfaces.
Polished surfaces are ideally suited to low abrasive areas and
historically are best utilized as vertical surfaces. If polished
surfaces are used as flooring, restoration type processes become
a normal part of regular maintenance.
|
Environment |
Kitchen
Areas : Kitchen areas are hostile environments. Stone
used in the kitchen should be as impervious as possible. Hardness,
loh absorption and easy wipe-ability are primary physical characteristics
necessary for long life and utility.
Bath Areas Stone inside showers and around
tub areas should be smooth and low absorbency. Polished surfaces
require special care in wet areas. Think of stone installations
in the bath area as you would a plumbing fixture - you want
a smooth, easily wiped surface that is easy to sanitize and
requires no special effort.
Hard water deposits can be very damaging to natural stone. If
you have hard water you should soften it. Chemical cleaners
should be carefully evaluated prior to using for compatibility
with the stone. Never use acidic type cleaners on marble or
limestone.
Exterior Areas Exterior stone will weather
sooner or later so expect some cosmetic changes over time. Polished
surfaces show cosmetic changes rapidly in most exterior situations.
Acid rain and pollution will attack natural stones - some more
readily than others. Carbonate based stones are most sensitive,
siliceous stone less sensitive as a rule.
Maintenance Budget The most economical stone
surface to maintain is one that does not show cosmetic changes
during normal use. On stone floors this means a non-reflective
surface since foot traffic tends to abrade at a grit approximating
120-220 grit. Polished stone surfaces re very stable cosmetically
if they are not subjected to abrasion and chemical attack. Non-polished
surfaces are more practical in areas that are expected to be
abraded, especially in high traffic areas. Match the stone finish
to the intended function and abrasion level if you desire low
maintenance costs.
There are situations where the design considerations will outweigh
the need for low maintenance costs and in these situations the
cost of restoration processes in addition to normal cleaning
need to be evaluated.
|
Preventive
Maintenance |
Cleaning
Methods
Sweeping
: The old fashioned broom is still a valuable part
of everyday maintenance of any floor surface - stone included.
It is very important to remove soils from flooring surfaces
before they get ground into the floor. Soils are abrasive. The
more often soils are removed the longer the floor will retain
the original appearance. Use a broom with a bristle that matches
your surface. A soft broom or brush is recommended for smooth
surfaces. A medium-soft bristle is ideal for textured surfaces.
Vacuum : A good vacuum cleaner works better
on textured surfaces than a broom and is very efficient. Use
a vacuum on any horizontal surface when large areas are involved
as it is faster than sweeping in most cases.
Damp Poming : A damp mop is capable of picking
up microscopic abrasive soils and potential staining agents.
Damp mopping is recommended for most smooth surfaces on a regular
basis. Best done after sweeping or vacuum.
Washing :It is necessary to wash a floor regularly.
The job conditions will dictate frequency. The most frequent
problems encountered with stone floors are related to the floor
simply not getting effectively washed often enough.
Rinsing : Rinsing is one of the most critical
steps in regular floor maintenance. Dirty mop water residue
is common and a cause for much complaint. A two bucket rinse
method is highly effective in keeping floors from graying out
due to soil residues.
Cleaning
Chemicals
Soaps : Natural soaps are low-tech, inexpensive
and user friendly. They are also capable of providing a sealing
and/or dressing function for stone floors. Vegetable based soaps
are best. Specialty soaps formulated for use on stone are highly
recommended and desirable on most natural stone floors and other
stone surfaces.
Detergents : These are synthetic surface-active
agents (surfactants) that are very good at picking up soils
and emulsifying grease and oil. They make water "wetter" and
more effective for cleaning purposes. The detergent used for
stone cleaning should be carefully evaluated for compatibility
with the stone. Detergents are typically used with water and
may determine the pH of the cleaning solution. Detergents tend
to leave the stone very "raw" or absorbent and residues will
make water penetration into the stone more effective.
Acids : These are used for removing grout
haze, removing mineral dposits and for rust removal. Acidic
products attack lime and cement. Use caution with acids and
acidic pH products as they attack the polish on marnbles and
limestone. Phosphoric acid, citric acid and sulfamoc acid is
preferred to muriatic, sulphuric and hydrocloric acids in almost
all situations due to safety and control issues.
Abrasives : Abrasives are sometimes useful
as a cleaning agent but should be limited to non-polished surfaces.
Abrasives may be combined with detergents or soaps for scouring
a surface and removing thin layers from the surface. There are
many different types of materials used as abrasives - soft abrasives
may be composed of nut shells or feldspars, hard abrasives can
be silica quartz, carbide or even diamond.
Bleaches : Bleaches are typically oxidizing
agents (generate oxygen) and are useful in stain removal. Enzyme
types are available which are non-hazardous.
|
Preservations |
Sealing
Water
Repellents Silicone (synthetic oils) : Generic synthetic
oils which tend to leach from surfaces and migrate. Of limited
use due to the tendency of attracting dust and limited life
expectancy .There are many types but you can generally rely
upon the fact that you get what you pay for. This type also
darkens many types of stone surfaces.
Siliconates : Water based silicone derivative
useful for light colored, porous stone. Inexpensive.
This type should not be used on dark colored stone or important
surfaces. Any residues not absorbed will disfigure surface with
a salt-like precipitate. May be useful for some limestone and
concrete surfaces. Only water beads. Re-coating is not possible
due to the fact that it repels itself.
Siloxane : These are state of the art today
in long life and high vapor transmission. Moderate cost. Used
primarily for exterior stone surfaces including marble, granite,
limestone, slate and cement based building products as well.
Suitable for clay pavers and roofing tiles. Highly recommended
for most surfaces exposed to weather and/or high humidity. Does
not darken most surfaces. Solvent based is normal. There are
some new emulsions available which can comply with VOC restrictions.
Stearates :This is the cheap water repellent
sold to consumers in chain stores and hardware stores for wood,
concrete, masonry etc.. Performance is poor and short lived.
Not recommended for most building stone.
Oil Repellents : These are proprietary products
which repel oil as well as water and other liquids. There are
a number of these specialized products designed for use on stone
surfaces. Most are fluoroplymer-based but there are some other
types (rather exotic)
Drying Oils : These are the original natural
polymers. They include Tung , Linseed and Soy. These oils become
solid as they dry and are of potential use for sealing stone
surfaces. They are organic and hence they are relatively sensitive
to aging and may (read: will) yellow with age but are useful
in some situations.
Waxes : Waxes may be natural or synthetic
and include Carnuaba, paraffin, montan, beeswax etc. They are
typically formulated into paste waxes or emulsions for sealing
purposes. Their effect is less than permanent and typically
they are re-applied on a regular basis.
Silicates : These are mineral glasses which
fill up pores and densify porous surfaces. Very useful for restoration
of stone which is under chemical attack or exterior weathering
as it can replace lost minerals (repair) and provide protection
from further degeneration. They are specialized materials which
require expertise to formulate and apply for predictable results.
Finishing
Dressing
Waxes : This category is primarily paste waxes
composed of paraffin, beeswax, and some synthetics. They can
be very effective for maintaining a shine and prevention of
stains. Some professional products contain dyes or pigments
which can be useful in bringing out or maintaining the color
of red, black and green stones (primarily for furniture). Carnuaba
based waxes may be suitable for some low abrasive surfaces and
is used in specialty maintenance products.
Coatings : Coatings are usually acrylics,
urethanes, epoxies, varnishes, lacquers etc. and have limited
use on natural stone however there are some typical uses of
these film forming polymers. The most common coating is the
janitorial type floor finish that is applied to floors to maintain
a physical barrier which isolates the stone surface from abrasion.
These coatings are considered temporary or sacrificial and are
used primarily because the coating is easier to restore when
it gets damaged than the stone surface would be without the
coating. In general, film-forming coating are avoided on natural
stone if possible.
Soaps : Soap is potentially useful in a number
of categories because of the residue that soaps tend to leave
behind. The residue can be utilized as a sealer in some situations
or may be intentionally built up and used as a natural paste
wax or dressing. Soaps are very valuable for maintaining stone
surfaces and in most cases are 100% reversible. Soap residues
"dress" or nourish a stone, preventing the stone from drying
out and being overly absorbent.
|
Restoration |
Consolidation
Natural
stones age and weather with time. Binding of loose particulate
is a desirable process when it is necessary to arrest degenerative
processes. Limestone and sandstone are both excellent candidates
for binding processes which replace lost minerals which hold
the stone together.
There are many types of potential binding agents including various
polymers (acrylic, urethane, silicones, polyesters etc.) as
well as mineral based silicates available. Caution must be exercised
in the evaluation of a potential binding agent as the physical
compatibility of the binder with the stone is critical.
Binding agents and processes are underutilized today primarily
due to lack of historical data regarding suitability and lack
of knowledgeable restoration specialists.
Filling
It is sometimes desirable to fill cavities in natural stone
in order to decrease maintenance costs, avoid mechanical trapping
of soils and contaminants or for design considerations.
Hardening : Some stones may be chemically hardened
in order to resist abrasion more effectively. Limestone may
be hardened by a number of chemical processes including silica
impregnators, silico-fluoride treatments, or binding processes
may give a hardening effect.
Strengthing : Stone strength is usually the
result of an increase in stone density brought about by binding
processes.
Grinding : Grinding is the historical method
of restoring a worn and weathered stone surface to it's original
cosmetic condition. It is also the pre-conditioning stage for
polishing with oxides. Silicon carbide and diamonds are the
most common abrasives used.
Polishing : This is usually a mechanical abrasion
process sometimes coupled with chemical action. A typical polishing
compound is composed of aluminum and/or tin oxides and water.
Oxalic acid is used as an additive for polishing some marbles.
|
|