V. SANDING AND FINISHING HARDWOOD FLOORS
A.
Before
floors are sanded and finished, make certain that nothing is done to get them wet and that
nothing is spilled on them.
Grease, oil, wax, and other oily substances, may seriously affect the
final finish. Coffee, tea, and
blood are among the worst stains and can be virtually impossible to remove.
B.
Acclimatization
If at all possible, allow at least
three days between completion of installation and sanding. This allows the wood to acclimatize and
any glue to dry thoroughly.
Failure to do so may result in "sunken" joints.
C.
Sanding
Because parquet has the grain of the
wood going in several directions and usually has woods of varying hardness
(some show the slightest cross grain scratch), sanding must be done with close
attention to detail. While the
following process is specifically designed for multi-directional floors, it
works well on all wood floors.
1.
The
first sandings can be done with a standard drum or belt sander and edger using
50 or 60 grit sandpaper. If the
floor is particularly rough, the first "cut" may require using 36
grit paper with the second cut using 50 or 60 grit paper. Passes should be done parallel to the grain
of the primary wood or field.
CAUTION: If a water-based finish is used,
steel wool should not be used as it will cause rust spots.
2.
The
next cut should be done with an 80 grit paper or sanding pad. A random orbital floor sander is
strongly recommended for this sanding and all further sanding and
scuffing. We have had excellent
experience with multiple-head, random orbital floor finishing equipment.
3.
The
next sanding should be done with 100 grit paper, sanding pad or screen. If a random orbital machine cannot be
obtained, a standard rotary buffer must be used for this and all
further work. Special attention
must be paid to swirls, cross grain and other sanding marks. While barely visible at this point, any
scratch will become glaringly obvious when the finish is applied.
4.
A final
sanding using 120 grit paper or pad may be appropriate.
5.
At this
point a strong light should be shined across the floor to highlight any
remaining scratches and a close check given for any other marks or
imperfections. A hand-held, random
orbital sander may be used to buff out these marks.
D.
Filling
When working with wood there are
always small gaps and fissures, nail holes and tear-outs. With a floor done primarily in a
commonly used wood such as oak, ash or maple, filling can be done with
commercially available putty. When
unusual or exotic woods are used, finding a ready-made filler that will give a
reasonable match and age like the actual wood is nearly impossible. The following steps should be followed:
1.
Putty
for fill should be made on site.
a.
Using
80 or 100 grit paper on the belt sander, grind up a chunk of each kind of wood
used. (Clean the sandpaper and machine between woods.)
b.
Put
several tablespoons of this sawdust in a small plastic cup and add some of the
finish material in small amounts, mixing well until it reaches putty
consistency.
2.
After
using the belt or drum sander (the first one or two cuts) fill using the
putty. Leave the putty
over-filled. When there is a space
at the joint of two different woods, it is generally better to use the darker
fill. You may have to
experiment. Allow to dry.
3.
Finish
sanding as outlined above. Apply
the first coat of finish. When the
finish is dry enough to walk on, but not fully set, reputty as needed. Allow to dry.
4.
Buff/sand
and apply second coat of finish.
Check and reputty, as needed.
E.
Staining,
Bleaching and Pickling
1.
Basically,
there are two types of stain.
Pigmented stains are ground-up solid pigments suspended in a
carrier. Dye stains are chemicals
dissolved in a solvent. The stains
are applied to the wood, allowed to soak in, excess wiped off, then dried. The carriers or solvents include
lacquer, mineral spirits, alcohol and water. Some seal the surface; some do not and should be followed
with a sealer. The selection of
the subsequent surface protection must be correct and therefore we recommend
that the work be performed by a professional.
2.
A
professional finisher can intermix "canned colors" by the same
manufacturer to create different tones.
The final finish selected will impact on the final color. You should not mix stains of one base
with finishes of a different base i.e., oil with water. While we do not recommend staining or
dying wood floors, if you must, keep the following in mind:
a.
Do not
rush the process: adequate drying time is critical.
b.
Do not
expect to stain a floor to match cabinets or furniture: the stain "takes" differently
because the dimensions, wear on the woods, and staining processes are very
different.
c.
Do not
expect a monochromatic floor: each
piece of wood in the floor is an individual and will accept the color
differently.
d.
Deep
scratches, spots worn through to the wood and repairs must be restained and may
never match the original stain.
3.
While
many people like the contemporary look of bleached or white/pastel-stained
hardwood floors, the National Oak Flooring Association, an organization
comprised of hardwood flooring manufacturers, says be forewarned. The attractiveness could be fleeting
and cause problems that won't occur with a natural or dark-stained hardwood
floor.
4.
One
problem common in bleached and white/pastel hardwood floors is the appearance
of cracks between the flooring boards.
All hardwood flooring expands or contracts with changes in humidity
levels, but the cracks that appear in dry seasons usually disappear when the
air is more humid and the flooring expands. Cracks are much more noticeable with artificially-lightened
floors.
5.
Bleaching
to achieve an exact hue cannot be assured with a natural wood. Use of white or pastel stains is the
other method of creating a light colored floor. However, natural variations of wood grain and texture do not
accept the stain uniformly and stains do not always produce the same color as
shown on the color card.
6.
Bleaching
also can interfere with adhesion of the surface finish. Often, chemicals in the wood will have
a reaction with the bleach.
Several years after installation, discoloration and black splotches may
"mushroom" up under the finish.
In addition, bleaching can soften the surface of flooring.
7.
Because
of the greater labor and time required, contractors usually charge considerably
more if a light-colored finish is specified. A few contractors are refusing to accept such jobs, and
others include in their contract a waiver of responsibility for the final
appearance of the floor.
8.
Maintenance
is another consideration. Dirt is
a floor's worst enemy and it shows up more on a lightened hardwood floor. Runners and throw rugs may be needed in
high traffic areas because lightened wood floors show wear sooner. Follow a regular maintenance program
designed to keep floors clean.
9.
If you
want a light colored hardwood floor, we recommend choosing a wood that is
naturally light in color. If you
must bleach or stain, here are some things to keep in mind:
a.
Have a
competent professional install and finish it. See a demonstration panel or, better, a floor he or she has
done.
b.
Be sure
your client is prepared to make compromises like living with tiny visible
cracks or having the finish turn a slightly different color as it ages. This ageing process varies with
different types of wood.
c.
Don't
rush the floor finisher -- it may take as long as 10 days to achieve a good
light-finished floor because of the extra drying time the materials used require.
F.
Selecting
Finish for Hardwood Floors
The last step to a beautiful hardwood
floor is the finish. The finish is
intended to protect the wood from wear, dirt, oxidation and rapid exchange of
moisture. The selection of finish
should be done with care and with the advice of a professional. There will be certain systems each
finisher will favor based upon their expertise and experience. With good communication about the
client's desires and the finisher's advice, the proper selection can be made.
1.
Durability
versus hardness
The hardness of a wood flooring
finish does not necessarily make it the most durable. The most durable finish is the one which protects the wood,
adheres well, applies the smoothest, resists and does not show wear, and is
easily maintained and repaired.
Eventually any finish will wear and need to be renewed. You want to be able to do this
inexpensively and without having to sand down to the wood.
2.
Ultra-violet
rays (UV)
UV from the sun or florescent lights
will have an effect on most woods.
Most woods improve as this "patina" develops. Some, such as cherry, do not reach
their full beauty until after several years of exposure to the sun. On the other hand, some woods, like
teak, change color and heavy furniture, rugs, etc, can block the light and
leave "light puddles".
Finishes with UV block will slow down (but not stop) the effects of
UV: better polyurethane finishes
have UV block.
3.
Level
of Finish Gloss or Shine
a.
Finishes
range from gloss (high shine) to semi-gloss (medium luster) to satin
(matte/flat).
b.
A high
gloss floor shows scuffs, scratches. traffic areas and dirt much more readily
than the softer look of a satin, low-luster floor. It may also show dust, dirt and scratches and require
greater care. Aesthetically, while
a high gloss finish tends to obscure the natural character, texture and color
of wood, it may be appropriate in areas with poor lighting.
c.
A matte
finish is very flat, lessening the natural luster and depth of the wood. It may be appropriate in areas with extremely
strong light. Matt finishes are
highly likely to have slight streaking, even with the most careful application.
d.
A
semi-gloss finish retains the glow of gloss without the glare, and enhances the
natural luster and depth of the wood.
Properly done, it has the appearance of a freshly waxed and buffed
floor, the look most people expect from a wood floor. Many manufacturers now market a semi-gloss and many
finishers can blend gloss and matte for the finish most appropriate to the
space.
4.
Surface
or Penetrating Finish
a.
Surface
finishes, true to their name, lie on the surface of the floor and take all the
wear. When the finish is worn, the
floor should be sanded and another coat of finish applied. Surface finishes provide the wood with
varying degrees of protection against water spills and staining. However, only the top of the wood is
sealed, causing an unevenness in expansion and contraction, particularly when
the floor is installed on concrete or over dirt.
b.
A
penetrating finish sinks into the pores (vessels) of the wood. It allows some breathing through the
top, is easily renewed, but provides less protection. When combined with a surface finish, it accentuates the
beauty, depth, and richness of the wood.
5.
Finish
Types
There
are many different kinds of wood floor finishes available and the technology is
changing rapidly.
a.
Wax is the oldest, and in some ways the
best finish for wood floors. It is
the easiest to apply, least expensive, fastest drying, easiest to repair, and,
with proper care, will last forever.
Wax should be applied over a penetrating oil. Water will spot a waxed surface and frequent buffing is
required. Periodically the floor
should be stripped and rewaxed.
The alternates to wax developed
through the years are films which take the abrasive wear of foot traffic. When they wear out they should be
recoated to protect the wood.
b.
Shellac is seldom used today. It is alcohol-based, fast dry, and
repairable, but water marks and humidity turn it white.
c.
Natural
Varnish has good gloss, is easy to work and less
expensive but less durable and difficult to repair, high in VOCs (volatile
organic compounds; fumes which are noxious, even poisonous).
d.
Man-Made
Varnish has good
gloss and durability, but is difficult to repair, high in VOCs .
e.
Lacquers are now available in satin or gloss,
but do not wear well, are very difficult to apply, have noxious fumes and are
highly flammable, high in VOCs.
f.
Epoxy
Ester is all
man-made, good gloss, recoatable, hard and durable, and great for maple gym
floors. It is difficult to apply
properly, high in VOCs and very,
very expensive.
g.
Penetrating
Oil with Sealers and Hardeners is easily applied, gives soft, oiled-wood look, should be
renewed once or twice yearly based on use
but easy to do, provides limited protection, is highly recommended under
waxed floors. Because it is easily
repaired, it is an excellent choice for commercial and other high wear
areas. One coat is highly
recommended under other oil base finishes as it brings out the grain and
featuring.
h.
Moisture-Cured
Urethane has
excellent durability, is most wear-resistant of finishes, gloss only, smells
terrible and extremely weather-sensitive but only during application,
expensive, difficult to apply, requires very specialized application and is
loaded with VOC's.
i.
Acid-Curing
Urea Formaldehyde is
very durable, is fast drying and non-yellowing, called "Swedish
Finish", very difficult to apply, highly flammable, low flash point,
obnoxious odor, high VOC's, expensive.
j.
Water-Borne
Polyurethane is hard
but less durable than moisture-cured or oil polyurethane, comes in gloss or
satin, has "milky tone, kills woods natural luster and gives a "flat" appearance
to most woods, discolors many woods, grain raise requires careful attention by
the finisher. Fast dry, water
cleanup, non-flammable, non-yellowing, little odor, easy application, recoats
any existing finish except wax, expensive, , VOC compliant.
k.
Oil-Based
Polyurethane is very
durable, relatively hard, and comes in gloss, semi-gloss and matte-flat: better brands, contain UV blockers,
"speed dry" products are available, moderately easy application,
moderate VOCs. Brands using soy or
safflower oil based polymers are very low ambering, tung oil based polymers
will give darker tones.
6.
Application
of Finish
Whatever finish system you choose,
there are some basic guidelines which apply across the board. If you have questions, any reputable
manufacturer will be glad to give technical advice on the best procedure for
applying their product and most have a technical representative (tech-rep) you
can call.
READ THE DIRECTIONS ON THE CONTAINER. Application procedures can differ even with the same type
product from different manufacturers.
a.
Clean
the entire floor well before each application of finish. It is best to vacuum, wipe with
"tack cloth", spot check with a clean rag and retack entire floor if
any dirt shows on rag. With water
based finishes a damp terry cloth rag makes an excellent tack cloth.
b.
Whenever
possible, the finish should be applied with brush or applicator strokes
parallel to the direction of the grain of the primary wood or field.
c.
We
recommend that oil-based penetrating sealer be used for the first coat. This gives the floor depth and
"life" and helps many woods hold color. It can also deepen the color, so test on a scrap piece of
each wood first. Waterbase sealers
will not do this.
d.
If the
floor is "scuffed" (lightly sanded) between coats, step 2 must
be repeated immediately before the next application of finish.