When
was last time you used shellac in wood-working?
Many years
ago, shellac and varnish
were the only options in
furniture finishing. Newer ‘Poly’ finishes
have gained momentum because they offer
much greater ease in application. The flake
form has especially waned in popularity with
woodworkers, because it is very labour inten-sive
to use. However, I would still suggest
you keep some shellac on hand. It does have
a few advantages, especially if you do any
amount of woodworking with pine.
What is shellac?
Shellac is
a natural substance made from the secretion of an insect called
the ‘lac’ beetle,
which is native to India and some Asian countries. The secretion
is collected
from a variety of tree leaves which host the
beetle. The beetle burrows into a leaf,
sucking out the juices for nourishment and
then secreting a resin, which hardens into a
protective coating. This coating is collected,
crushed and dried. Chemicals are added and
then it is drawn out into sheets called shellac.
The time of harvest, the processing, and the
source, determine both the grade and the
colour of the finished product.
Shellac In
Woodworking
Shellac comes
in two forms, ready mixed and flakes. Ready mixed is either in
liquid
form or in spray cans and contains a
preservative, to give it a longer shelf life.
Shellac, being a natural product, deteriorates
rather quickly. Ready mixed shellac contains
other additives, such as drying retarders
which allow for brush applications, and
levelers which will hide brush marks.
The flake form is mixed with denatured
alcohol. |
It
is made in small quantities, which can be used up in a short
period of time.The
flakes are available in at least four types: clear, orange and
several ranges of dark. Luthiers, those who make violins and
guitars, still use shellac in flake form, almost exclusively,
in a long process called “French Polishing”. It is,
sadly, a dying art. However, there are still woodworkers who
will persevere to achieve the very deep, high gloss finish it
gives to wood.*
The “Cut” In
Shellac You have probably heard
the term “cut” referring
to shellac. Cut refers to the proportions of shellac flakes and alcohol
when mixing shellac. For example, a one
pound cut (written as 1# cut) is one pound of
shellac flakes mixed with one gallon of
alcohol. A 1# cut is generally used as a “spit” coat,
which is a thin primer coat of shellac. A 2# cut is two pounds
of flakes to one gallon
of alcohol, for a thicker mixture.
You would never mix a gallon of shellac,
though. It would be a hardened mess in the
container before you even came close to
using it up. Mix smaller quantities using
the same ratio. A pint of shellac is more than
enough to finish say, a guitar, with about
10 coats.
To help you with the mathematics for a
2# cut, try this: mix four ounces (1 pint) of
flakes into 1 pint of alcohol. In order to mix
the flakes and alcohol into a usable liquid the
flakes should first be ground into a fine
powder or, if you prefer, leave the flakes and
alcohol to blend for 24 hours. The results will
be the same.
A faster method is to put the mixture into an
airtight mason jar and sit the jar in hot tap
water. You will have to change the water
several times and shake the mixture often.
A word of caution, however: Never use
boiling water, a microwave or a hot stove
element to hasten the process. |
Advantages In Using Shellac
Shellac, used for woodworking,
has had the natural wax removed during processing,
which makes it a perfect medium for bonding
dissimilar finishing products. When you are
not sure what type of finish has been used in
a re-finishing project, use a ‘spit-coat’ of
shellac first. Shellac will bond to anything,
except wax.
Shellac is also very easy to repair. Shellac
can be used as a wood conditioner to ensure
an even absorption of wood stain.
Use shellac as a moisture barrier to seal the
ends of green wood to prevent cracking and
splitting.
Shellac should be used on knots in pine
and other wood species to prevent
‘
bleed-through’.
When stripping porous wood, use shellac
on those areas that have ‘pits’ of stain or
finish left in them. Wait an hour and then
apply more stripper. The shellac will ‘lift’ those
areas clean.
Shellac VS
Lacquer
Lacquer is
an emulsifying product. In other words, each successive coat
chemically
amalgamates with the existing finish.
Shellac bonds to the previous coat but ‘sits’ on top of it giving a ‘deeper’ finish.
Shellac won’t ‘yellow’ over time and it can be
re-coated in about two hours. Shellac is
non-toxic when it is dry so it can be safely
used on salad bowls and the like. |
