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This section contains technical information and advice
on everything from sanding equipment and abrasives to floor
coatings and maintenance products.
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APPLICATION OF BONA
FINISHES
Best application results can be achieved by using a Bona applicator
or Bona waterborne roller. The choice is up to you.
Tools and mixing vessels
Avoid using a brand new roller or applicator to apply a final
finish coat. If unavoidable, prepare the roller or applicator by
rubbing quickly by hand for a few minutes to remove loose fibres
then wash roller thoroughly in warm water and repeat. Trim the ends
of the roller with a sharp pair of scissors if necessary.
Room Temperature
Must be between 12 degrees celsius and 30 degrees celsius during
application and whilst drying. Mask off windows to avoid areas of
direct sunlight. Low temperatures combined with restricted air
circulation will result in increased drying times.
Ventilation
Slightly open windows to ensure proper air circulation during
drying, especially in colder weather. Keep windows closed during
high temperatures.
Coverage
8-10m2 per litre per coat. It is very important that the correct
coverage rate is observed as the performance of Bona finishes are
in direct relationship to the amount of material applied to the
floor. It is very easy when using waterborne finishes to apply too
little. Always apply at the rate of 8-10m2 per litre per coat.
Drying Time
1-4 hours per coat at 20 degrees celsius/50 per cent relative
humidity until surface can be abraded. The floor will take light
traffic in socks after 12 hours but will not reach ultimate
hardness for 10-14 days - sometimes longer in cold weather.
Abrasion between coats
Bona sealers need to be sanded, however if this is necessary, use a
Bona Scrad and Scrad Wing and move the rotary machine quickly over
the surface. When applying 3 coats of finish it is usually only
necessary to sand prior to final coat. Lightly abrade the floor
with a 220 grit screen or Bona Scrad. When using a rotary machine
it should be moved quickly and lightly over the surface. It is
preferable to use a machine with a buffing speed of 240 rpm or
slower. Carefully remove all sanding dust, etc. by 'tacking off'
with a Bona tack mop prior to final Bona finish application.
Clean-up
Tools should be cleaned thoroughly in cold water immediately after
use. Use acetone for dried finish.
Storage
Store away from frost and heat (Do not leave product in vehicles in
warm weather).
Shelf Life
At least one year in un-opened original container.
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CORRECT SANDING TECHNIQUES FOR
WATERBORNE FINISHES
When using solvent polyurethane finishes on newly sanded floors, a
degree of 'grain raising' is always apparent. This is particularly
true for waterborne finishes. There is no current technology that
will eliminate this, but by following the steps below, you will
significantly reduce the amount of grain raising when using Bona
finishes.
1. Sanding
Ensure the floor is sanded level by always angle cutting first.
Make sure your last sand is with 120-150 grit abrasive. We
recommend always finishing with 150 grit on softer timbers like
Baltic Pine, Radiata Pine, Oregon and Tasmanian Oak. Use of a Bona
Scrad (equal to 320 grit) as a final procedure will further reduce
grain raising.
2. Final Sanding
Complete your sanding with a 150-220 grit screen or Bona Scrad and
Scrad wing. This will 'burnish' the wood and reduce porosity as
much as possible. Very simply, the less water penetrating the
surface, the less swelling of the wood fibres that can take place.
Less penetration of the finish into the wood will also allow for a
higher film build.
3. Application of Sealer
Apply PRIME as per instructions. Do not apply sealer too thickly.
If necessary, sand PRIME using the Bona Scrad system. Allow to dry
thoroughly before applying the next coat - otherwise a white
discolouration may occur. This discolouration usually disappears
when the finish dries.
4. Abrading between coats
Abrade prior to application of final coat with a 220 grit screen
disc or Bona Scrad. Remember to move the rotary machine quickly
over the surface. Moving the machine too slowly over the floor
builds up heat caused by friction, which can result in softening of
the finish. This may cause clogging of the screen or Scrad. (This
is because all waterborne finishes are 'thermoplastic'). Try to use
a machine with a rotary disc speed of 240 RPM or slower.
A technique sometimes used to guarantee minimal grain-raising on
very dry or very soft timber such as Baltic Pine is to spray the
floor with a fine mist of water just before the final rotary sand.
This deliberately raises the wood fibres and results in far less
grain raising when the finish is applied.
Using BONA Waterborne
finishes in high temperatures
1. Before application - Control the temperature! Keep the
interior temperature below 30 degrees celsius - use air
conditioning if possible to bring down room temperature before
application. Do not run air conditioning while applying finish.
2. Mask off all sliding glass doors or large windows to
prevent sunlight from heating the floor. Even in a cool room, where
there is direct sunlight, the floor can become extremely hot. If
applying Bona finishes in such conditions the levelling agents will
dissipate too rapidly and prevent the finish from naturally flowing
and levelling.
3. In areas of extremely high temperatures, you may add 5%
of water to the finish. This amount will not affect the levelling
and flow properties of the finish but will extend the working time
for application. However, only add water in extreme situations and
under no circumstances add more than 5% (50ml per litre). Again be
sure to apply finish at the correct rate.
4. During application...
In warm conditions apply the finish liberally. Applying heavy coats
will allow more working time. Do not apply thin coats or 'overwork'
the finish. Always apply at the correct rate of 8-10m2 per litre.
Do not open windows during application as this will shorten drying
time - keep windows closed.
5. Use of a Bona applicator in place of a roller will reduce
the risk of bubbles drying in the finish during extremely hot
conditions.
Important note
While transporting Bona waterborne finishes to a job site, it is
possible for the temperature of the product to become excessively
warm. Allow the finish to cool down to room temperature before
application. Do not store in work vehicles.
Remember
If the temperature outside is 30 degrees celsius or greater, the
temperature inside your car, truck or van may be more than twice
that when sitting outside in the sun. Do not leave Bona waterborne
finishes in these high temperatures. Always store in a cool
place.
Trouble
Shooting
Sometimes unforeseen problems occur when coating a floor with any
floor finish, but it is usually relatively easy to identify the
cause. Here is a guide to the most common difficulties when using
waterborne polyurethane and how to avoid them.
Abnormal grain raising
The final sanding was done with sandpaper that was too coarse.
Too much finish was applied for the first coat.
The timber was
extremely dry.
The timber was very soft - the temperature was very low.
The floor was not sanded completely level.
Please note
Use 120 grit or finer sandpaper for final sanding.
We recommend using at least 150-220 grit for softer timbers like
Baltic Pine, Radiata Pine, Tasmanian Oak, etc. Use the 'spray
technique' -
Use the recommended amount of finish.
Unsatisfactory levelling out
(leaving brush strokes and imprints from applicator or roller)
The finish was applied too thinly, causing finish to dry too
quickly.
High temperature and low humidity can cause the finish to dry too
quickly.
The floor was too warm due to direct sunlight - windows not masked
off.
The finish was too warm or too cold.
Windows were open on a warm day.
Blisters and Bubbles
The finish has dried too quickly.
The finish was applied too thinly.
The finish was not at room temperature.
The floor was too warm due to direct sunlight.
The finish was too old or stored incorrectly and the de-foaming
agent stopped working.
Please note
Use the recommended amount of finish.
The floor and finish should be a normal temperature.
Mask off windows to avoid direct sunlight.
Keep windows closed in warm weather.
Observe shelf life of product and always store in cool place -
never leave in work vehicles.
Adhesion problems following re-coating
Floor has been treated with wax or polish.
No abrading done first.
Floor abraded but not thoroughly enough.
Please note; Always use Bona Cross-Linker whenever re-coating using
Mega.
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RE-COATING PRE-FINISHED AND
PREVIOUSLY SANDED FLOORS
Bona products normally have an excellent adhesion to pre-finished
and previously finished surfaces. If in any doubt always check the
adhesion on a small area first.
1. Prior to application the surface must be clean and free
from wax, polish, grease, dirt and other contaminants.
2. Lightly cut back the surface to provide a 'key' using a
220 grit screen or a Bona Scrad and Scrad Wing (especially when
coating a pre-finished surface).
3. Carefully remove all sanding dust by sweeping, vacuuming
and finally 'tacking off' by wiping over with a damp cloth. (A Bona
Timber Floorwipe is excellent for this purpose).
4. Apply 1-2 coats of Bona MEGA or TRAFFIC (lightly abrading
between coats if necessary). It is recommended when coating
pre-finished flooring to always use MEGA in conjunction with Bona
Cross-Linker.
NB: Waxed or polished floors should always be sanded back to
bare timber.
COATING OF NATURAL CORK
When coating cork tiles we recommend applying one coat of Bona
PRIME followed by 2-3 coats of Bona MEGA.
NB: Only use Bona finishes on high-density cork tiles. Never
use Bona finishes on low or mid-density cork tiles. Because of
variation in density of cork tiles, it is possible to experience
particle separation particularly with light coloured/low density
tiles. If in doubt check by sanding and coating 2 or 3 test tiles
first.
CARE AND MAINTENANCE
Bona finishes should be used in conjunction with a regular
maintenance program. Consumer expectations regarding the
performance of polyurethane floor coatings are often higher than is
reasonable.
Floor sanding contractors should adequately brief their customers
regarding what to expect from their floor coating. ie. it is not
indestructible and that preventative maintenance will keep the
floor looking better for much longer.
When coating a floor with Bona finishes your customer should be
presented with a copy of the Bona brochure that outlines how to
maintain their new floor. This should preferably be given to them
at the start of the job and not the end when it is often
forgotten.
After applying final coat
Floors will take light traffic in socks after approximately 12
hours but will not reach ultimate hardness for 10-14 days in normal
drying conditions - sometimes longer in cold weather.
Carpets and rugs
Should not be put in place until after 14 days. Avoid walking on
the floor with shoes for the first 48 hours at least.
Preventative Maintenance
The floor should be kept free of dust and grit by using a dust
control mop. Avoid using bristle brushes, brooms and vacuum
cleaners.
Entrance Mats
These should be installed inside and outside to remove grit from
the bottom of shoes.
Floor Protectors
Felt should be placed on the bottom of furniture to minimise
scratching and scuffing of floor surface. Bona Wood Floorgards are
ideal.
Cleaning
Remove dirt with a damp cloth or mop and use a neutral pH detergent
if necessary. Do not use abrasive cleaners. Never wet-mop a timber
floor. Bona Timber Floorwipe Kits contain a cleaner specifically
designed for timber floors and guarantees that too much moisture is
not applied to the floor.
Important: Do not clean the floor with damp mop until finish
is completely cured. At least 10-14 days depending on climatic
conditions.
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CHATTER MARKS
'Chatter Marks' is a well-known term in the floor sanding industry
all over the world. It describes a closely spaced repeating drum or
'ripple' mark which is visible in the floor following the sanding
procedure. Impossible to feel with the hand, chatter marks often
show up more obviously when the finish is applied to the floor and
can ruin what could otherwise have been a great job.
Many floor sanding contractors literally spend hours cutting these
chatter marks out of the floor with a rotary sander and while they
might succeed at removing the 'chatter', they create another
problem; circular marks in the floor which can look even more
unsightly than the original imperfection that they were trying to
correct. In any case, using a rotary sander to remove chatter marks
is one of the biggest time-wasters in the floor sanding industry
today. Understanding some of the causes of chatter marks and
knowing how to rectify them will enable you to improve the quality
of your work and save valuable time.
Worn or out-of-balance sander parts often create vibration that
produces chatter. These vibrations are often difficult to detect
while the machine is operating. Sophisticated vibration monitoring
equipment is the most effective way of detecting the source of any
problems rather than a time consuming trial and error process.
Regular machine servicing including cleaning and checking for wear
of drums, wheels, bearings, fans, pulleys, V-belts and belt- sander
roller systems is highly recommended. Whether you own a
conventional slotted drum or a continuous belt-sander, your
equipment must be well maintained in order to avoid chatter marks
that are commonly caused by one or more of the following;
(a) The sanding drum. This is often the first place to
start. Before balancing is carried out, the technician can
ascertain any drum run-out to indicate that the drum is
'out-of-round'. This should be rectified before any balancing work
is done.
(b) Bearings. Check all the bearings with the machine turned
off. It is often not the bearing itself, but worn bearing housings
that can cause vibration problems.
(c) Fan blades. Often operating at speeds of up to 8,000
rpm, even the smallest chip on a fan blade will produce
vibration.
(d) V-belts. Worn or cracked V-belts should be changed.
Routine replacement once a year is a good rule of thumb.
(e) Motor. Vibration could emanate from an out-of-balance
rotor shaft. Likewise, drum mounting shafts that have been knocked
or are worn may need re-balancing or replacing.
(f) Pulleys. An unbalanced pulley will also cause vibration.
Worn or chipped pulleys should be replaced.
(g) Drum condition. Check that the drum covering (either
rubber or felt) is in good condition with no signs of delamination.
Before having the drum dynamically balanced, it should be
thoroughly cleaned. Depending on the drum design, it may be
necessary to use compressed air to blow out months and perhaps
years of dust build-up. This super-fine dust can collect inside the
drum and cause imbalance; most commonly with conventional
drums.
(h) Rollers. If you have a belt sander, the roller assembly
should be removed, cleaned and checked for smooth operation. Look
for wear and check that the bearings are running smoothly.
Servicing the upper roller should be carried out at regular
intervals.
(i) Wheels. Check all wheels for dirt or hard filler that
may be adhered. Use a scraper to gently remove putty or a solvent
soaked cloth to dissolve dirt. Wheels should be checked for flat
spots and being out-of-round. You might go so far as to leave the
machine with wheels off the ground when not in use.
(j) Conventional drums. For many reasons, these seem to be
more prone to leaving chatter marks than continuous belt drums. The
most obvious difference is the large gap in the drum. If you use
packers (strips of sandpaper) to help get the paper tight, try
placing them behind the end flaps of the sandpaper, instead of
between the flaps. This will reduce the size of the gap slightly.
Having the paper too tight or too loose may also affect the amount
of chatter. Experiment with different tensions to get the best
results.
(k) Uneven paper tension. This will be obvious if the paper
is tighter at one end of the drum compared to the other. Uneven
tension will contribute to vibration and can often be heard as a
flapping sound when the drum is lowered to the floor during
sanding.
(l) V-belt tension. Assuming they are in good condition, try
tightening or loosening the V-belts. This can reduce overall
machine vibration and chatter marks as a result. Pay particular
attention to the smaller V-belt that drives the fan. This is often
overlooked and can contribute noticeably to machine vibration.
(m) Excessive drum pressure. Using too much drum pressure,
especially when fine sanding, can cause the left or right wheel to
leave the floor which results in uneven drum pressure. Using the
lowest setting when fine sanding will give you a much better
result. It is often not a good idea to put extra pressure on the
drum by pushing down on the drum pressure handle or pulling up on
the machine, especially when walking backwards.
(n) Worn abrasives. If the sandpaper is worn, the floor can
show chatter marks. Some contractors deliberately dull sandpaper to
'burnish' the floor. This practice is not a good idea if you want
to reduce chatter marks.
Ridding floors of chatter marks is often a matter of trial and
error. The difficulty is that they are often caused by a
combination of factors. Sometimes chatter marks are mistaken for
'waves'. In other words, ripples which are more widely spaced.
Waves are often the result of the sanding technique employed by the
operator.
(o) Sanding speed. The speed at which you allow the machine
to move is often critical to the final finish. Moving the machine
too quickly or too slowly can often create a wave effect in the
floor. Depending on the machine you are using, experiment by
walking faster or slower if 'waves' are a problem.
Thankfully, although customers will complain about scratches and
dust in coatings, edger marks and other imperfections in the floor,
it is rare to hear a serious complaint regarding chatter marks.
However, if your drum or belt sander is working as it should and
the correct sanding technique is used, you should be able to
achieve a finished floor that is ripple free.
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HEALTH AND
SAFETY
Fire Risks
Many fires have started in the dust bag of a sanding machine. To
avoid the risk of glowing embers in sawdust starting a fire, always
the bag into a fire proof bin away from any buildings of
combustible material. The use of kerosene to dampen timber or
sanding over exposed nails increases the fire risk. If you see a
spark, stop the machine and punch nails before continuing. Dust
bags have been known to catch alight while the operator has been
edging the floor. In other cases, a slow smouldering inside the bag
may continue for many hours before finally burning through the bag
and combusting. Basic rules for minimising fire risks are;
1. Never leave bags of sawdust in vans or next to
buildings.
2. Don't sand exposed nails.
3. Avoid the use of kerosene.
4. Never leave a part-filled dust bag on a machine.
The right protection
Working with solvent-based floor finishes poses specific health
risks. All of these finishes contain free monomeric isocyanates. It
is well known that isocyanates can cause severe health problems.
Ingredients used in all two-pack and one-pack floor finishes can
result in sensitisation, causing allergic reactions such as
shortness of breath or nausea. Solvent-based finishes can also
cause skin irritation, leading to dermatitis in some instances and
can be absorbed through the skin. For these reasons the Workcover
Authority recommends air-supplied respiratory equipment for the use
of solvent finishes. Despite this recommendation, most in the floor
sanding and finishing industry use half-mask respirators, with
filters specified suitable for organic vapours. At best, this type
of respirator gives minimal protection and in some cases none at
all. Filter life is limited and is dependent on how long you are
exposed, as well as the level of concentration. Filter life may be
only a few hours or less. Due to the poor warning properties of
floor finishes containing isocyanates, there is no way to tell if
the filter is spent. In these instances, you may as well not be
wearing a respirator at all. Half-face respirators often give the
wearer a false sense of security. Why the small number using
air-supplied equipment as recommended by safety experts? Lack of
education is one of the major reasons. Hopefully articles like this
can raise the level of awareness necessary to better protect
yourself against the dangers of working with solvent-based
finishes. It should also be noted that: if you are an employer, you
have a legal Duty of Care to adequately inform and protect your
employees and your customers. Check with a professional safety
equipment supplier that you are using suitable equipment to ensure
adequate protection. As an alternative, forget about respirators
altogether and consider using non-toxic waterborne finishes.
Turn Off Pilot Lights
Read the label on any drum of solvent-based finish and you will see
the warning; "All sources of ignition including pilot
lights must be eliminated". It is common sense. It is also
very easily forgotten. Every year in Australia many floor finishers
learn the hard way that solvent finishes are highly flammable.
Why don't we hear about it more often? It's understandable that the
people involved often choose to keep these stories to themselves.
The fact is, these types of flash fires happen many times every
year. Apart from possible physical injuries, the consequences
include the need to totally re-paint affected rooms and re-sand the
floors; all at the floor sanding company's expense of course! Even
if you always follow a strict safety routine, it is a good idea to
inform your customer. One company returned the next day and applied
the next coat without realising that overnight the customer had
turned the pilot light back on. You can guess the result. If you
are using flammable finishes, make it a part of a strict routine to
turn off all pilot lights and other sources of ignition. Otherwise
use a non-flammable waterborne finish and have one less thing to
worry about.
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TOOL TIME
Super flat sanding with Mirka double-sided discs
Looking for a way to get your floors dead flat in less time?
Mirka double-sided discs are an ideal way for getting all your
floors exceptionally flat - particularly parquetry, borders and
cork as well as strip and plank flooring. Also, the rigidity of
these discs provides a more aggressive and cleaner cut than
traditional single-sided discs or screens, and you don't need a
separate drive disc to run them. All you need is a rotary sander
and a foam or white pad to grip the disc, using the disc as you
would a regular screen.
Because Mirka double-sided discs are more aggressive than screens,
you can even move up a grit (i.e. use a 120 grit disc if you
usually use a 100 grit screen). Drive the disc with the pad on the
bottom of your rotary. When one side begins to dull, simply turn
the disc over for a fresh cutting surface. Say goodbye to messy
disc cement or spray adhesive forever.
You will find that a big benefit of Mirka double-sided discs is
that they will not 'dish out' the soft grain, always leaving a very
flat, even and smooth floor. Ask for Mirka double-sided sanding
discs from your nearest Ezi Floor Products distributor.
How to minimise swirl marks
One of the major reasons for customer call-backs, is swirl marks
visible in the floor. These blemishes are either scratches in the
timber itself, or in the coating. Abrading a finish coat that is
still not fully cured, means that even the use of fine abrasives as
high as 220 grit, will not guarantee a swirl free result. Screen
discs are commonly used, in the belief that this type of disc will
keep scratches to a minimum. In fact, the opposite is true. The
open mesh configuration of a screen disc, can actually produce a
more 'wild' scratch pattern that is more obvious than scratches
left by a conventional closed coat abrasive. Of course, customers
should always be properly informed that low-voltage down lights
will make a totally scratch free finish very difficult to achieve.
However, when abrading high gloss finishes, the use of screens
often leaves scratch marks that are unacceptable. A far better
method for sanding between finish coats is to use the Bona Scrad
system. A Scrad disc is a cross between a screen and a pad, with a
320 abrasive grit, mixed into a super-fine scouring material.
Depending on the degree of abrasion required, additional Scrad
'Wings', ranging from 120 grit to 220 grit can be attached to the
Scrad. These Wings are made of a special abrasive, designed to
resist heat build-up and reduce clogging. If your aim is to
minimise swirl marks, there is no better method than the Bona Scrad
system.
Moisture Meters - Why every floor sander should have one
The issue of edge-bonding has been a hot topic in recent times.
This phenomenon occurs as a result of a combination of timber
shrinkage and the glueing effect of polyurethane floor coatings.
The result is an unsightly clumping effect, with a number of boards
bonded together and large gaps between un-bonded boards. In extreme
cases, the result can be severe splitting within the boards. The
timber industry has responded by recommending that Tung Oil type
seals be used instead of polyurethane. The down side is that these
finishes have extremely poor wear properties unless regularly
maintained. Better wearing polyurethane finishes can be used and
the risk of edge-bonding greatly reduced by ensuring that the
timber has reached the correct Equilibrium Moisture Content (EMC)
before sanding and finishing commences. This is impossible to
ascertain without a proper moisture meter. Here is one example
where a moisture meter proved invaluable. A floor sander in
Adelaide was about to finish 100m2 of Tasmanian Oak flooring with a
polyurethane coating. The timber had been delivered to site with a
supposed moisture content of 12-14% and correctly acclimatised.
Installation had been completed for some weeks. As a precaution,
the floor sander took moisture readings that showed a moisture
content of between 13% and 16%. As a result, the work schedule was
revised and the sander returned some weeks later when the floor had
reached a much lower EMC. If the floor sander had finished the
floor without checking the moisture content, timber shrinkage would
certainly have occurred. The result would have been some degree of
edge-bonding. The floor sander could very well have been asked to
take responsibility. Why take the chance? A moisture meter is an
excellent investment and should always be used in conjunction with
timber correction figures to ensure accuracy. Ezi Floor Products
can supply timber moisture meters from between $250 and $450. Phone
1800-626-001 for more details
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TRADE TIPS
Don't Get Ripped Off
It's amazing how much floor sanding equipment is stolen each year.
Check with your insurer that you are covered for equipment stolen
from vehicles or job sites. A good insurance policy will also cover
you for damage to machinery as a result of a collision or
overturned vehicle. However, always ensure that your vehicle or job
site is locked, otherwise you may find it difficult to claim.
It's also important to have a record of machine serial numbers and
it's a good idea to consider letter punching the serial number in
an inconspicuous place on your machine. That way you will be able
to identify your machine if it is recovered. Most thieves will
remove the factory serial number to make the machine more difficult
to trace.
Never leave equipment on vacant job sites over-night and always
ensure vehicles are locked when unattended. That way you will
significantly reduce the risk of being ripped off.
Join an Association
There are many advantages in being a member of a trade
association.
You will find a floor sanding association in every mainland
Australian state. While they might have slightly different names,
the stated aims of every timber flooring association are very
similar: To provide a code of practice, training, education,
support and to raise the standard and image of the floor sanding
and finishing industry. Some of these associations might not be
perfect, but it's always easy to sit back and criticise. Get
involved. All of these associations have executive committees and
always appreciate contributions from new members. If you want to
find out how to contact the association in your state, call Ezi
Floor Products and we'll be happy to provide details.
Minimise Grain-raising
If you use waterborne finishes you'll know about the problem of
grain-raising. One technique to reduce grain-raising, is to spray
the floor thoroughly with a fine mist of water just before the last
rotary sand. The idea is to deliberately raise the wood fibres
before the final sanding process with for example, 150 grit. You'll
get far less grain-raising when the first coat of finish is
applied. Results vary according to timber species, but this
technique works extremely well with soft timbers like Radiata and
Baltic Pine. It might seem like a lot of extra work but it can
actually save time because there is often no need to sand the first
coat.
Don't make your samples look too good
It is a good idea to make sample boards to show customers examples
of various timbers and finishes. However, don't make them look too
good. If you produce samples that look 'perfect' by sanding
smoother, or applying an extra coat of finish, your customer has
every right to expect you to duplicate that standard on the floor.
Samples that show slight sanding marks and a few specks of dust
will be a more accurate reflection of how the floor will look.
Place the samples on the floor to demonstrate how the finish will
look from a standing position. Make sure your samples are realistic
and your customers won't have unrealistic expectations.
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UNDERSTANDING ABRASIVES
Abrasive Grits
There are 3 main types of grit used in the manufacture of flooring
abrasives. For many years Aluminium Oxide and Silicon Carbide grits
have been most commonly used. More recently, Zirconia grit has been
introduced to the floor sanding industry in Australia and has been
well received due to its' longer wearing properties. Its'
distinctive blue colour makes it stand out, but it is important to
realise that Zirconia grit is very expensive and is therefore mixed
with a cheaper grit like Aluminium Oxide to keep the cost down.
However, there is no industry standard that states what this ratio
should be. For example some 'blue' material contains as little as
10%-30% Zirconia grit. On the other hand, Mirka's 'Mirkon' brand is
a 50% Zirconia and 50% Aluminium Oxide mix.
When you're comparing brands remember, as a general rule the higher
the price, the more Zirconia content and the better the
performance. When it comes to abrasives, you really do get what you
pay for.
Electrostatic bonding
Better quality abrasives are electrostatically bonded with the
process of applying the abrasive grains to the backing material
performed in an electrostatic field. The electrostatic process
guarantees an even distribution of grit on the backing material and
means that the sharp cutting tips of the grit remain in a vertical
position. This process ensures a better quality sanding result.
Closed Coat versus s Open Coat
The amount of abrasive grit applied to the backing determines
whether the coating is closed-coat or open-coat. A closed-coat is
one in which the abrasive grains completely cover the surface. An
open-coat is one where the grit covers between 50% and 70% of the
surface with visible gaps between the individual grains. Open-coat
products have greater flexibility and resistance to clogging than
closed-coat. However, closed-coat products cut more aggressively
and have an increased working life. Closed-coat products are the
most suitable for timber floor sanding applications.
Anti-Static Products
Some abrasive products are put through a special process to prevent
the build-up of a static charge that attracts sawdust and causes
the abrasive to clog prematurely. In the next edition of The
Sanding Scene we will examine in more detail the differences in
abrasive backing materials.
UNDERSTANDING FINISHES
Which
finish?
Many customers these days are asking for their floors to be
finished with a 'Tung Oil' finish. The reason is often because they
want to avoid the thick 'plastic' look of a solvent based
polyurethane finish and prefer the more natural appearance of Tung
Oil products. What they often do not realise is that Tung Oil
finishes do not wear very well. No matter what brand, a Tung Oil or
Oil modified finish should be maintained with a sacrificial polish
to provide good wear resistance in high traffic areas. This
immediately creates an ongoing maintenance program for the
customer. The use of a polish also makes re-coating in the future
very difficult.
Waterborne
finishes
Just as "oils aint oils", not all waterborne
finishes are the same. With the increasing popularity of waterborne
floor finishes, it is important to know the differences. There are
many different factors that influence the performance of a
waterborne finish. Of major importance is what is left on the floor
after the finish has dried. This is known as the binding agent or
dispersion. In simple terms, a dispersion is the plastic material
that floats in the finish. This can be likened to very small
plastic balls floating in water. As the finish dries, the small
plastic balls stick together and form a film. There are a number of
different types of dispersions used in waterborne finishes
today.
1. Acrylate dispersion: Used in the very first waterborne
finishes 20 years ago. Acrylate is cheap, but has poor wear
resistance.
2. Polyurethane dispersion: Very wear resistant, but
expensive. Has a poor resistance to water.
3. Polyurethane/Acrylate mix: This type of finish is very
common. Price differences between products are based on the ratio
of more expensive polyurethane to cheaper acrylate. The more
polyurethane, the better the wear factor and the higher the
price.
4. Co-Polymer dispersion: In simple terms, this is a
dispersion where the plastic balls are made of acrylate on the
inside and the wear resistant polyurethane on the outside.
Finishes based on any of the above dispersions form a finish film
by 'physical drying'. In other words, as the water and small amount
of solvents evaporate, the plastic balls glue together. Where does
a cross-linker come into the scheme of things? These additives have
no effect on how the finish dries. However, by adding a
cross-linker to some finishes, it is possible to improve certain
finish properties, such as resistance to chemicals or scuff
marks.
BonaTech Mega is a waterborne finish based on a completely new type
of polyurethane dispersion, developed by Bonakemi AB in Sweden.
Mega uses a chemically curing dispersion. After the water has
evaporated, the 100% polyurethane binding agent reacts chemically
with the oxygen in the air. The end result is an extremely wear
resistant finish. Next time you are deciding which brand of
waterborne finish you should use, be aware. There are
differences.
Common misconceptions
When it comes to the performance of floor finishes, there are many
misconceptions. The most common misconception with solvent-based
polyurethane finishes is that a 2-pack wears better than a moisture
cured (1 pack) finish. The main reason for this misconception is
that many people confuse hardness with wear resistance. Yes, a
2-pack polyurethane will cure to a harder finish, but it will not
offer the best abrasion resistance. This characteristic hardness
means that 2-pack finishes lack flexibility and as a consequence
are not recommended by the manufacturers of cork tiles. The fact
is, if you are making a choice, a moisture-cured polyurethane wins
every time.
When it comes to waterborne finishes a common misconception is that
all brands are basically the same. The fact is, unlike
solvent-based finishes, different waterborne products are based on
a variety of technologies. Most of the better quality waterborne
finishes on the market in Australia contain a mixture of acrylic
and polyurethane and are known as 'co-polymers'. This technology
has been around for more than a decade and produces finishes that
offer good resistance to wear. More recent advancements mean that
the best waterborne finishes are now 100% polyurethane. Finishes
such as Bona Mega or Bona Traffic offer wear resistance comparable
or better than solvent-based products. Considering the added
benefits of being non-toxic, non-yellowing and quick drying,
without the need to vacate premises, it's easy to understand why
these finishes are becoming the first choice with home-owners and
flooring contractors all over Australia.
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