Varnish is a protective clear finish made from plant resins and solvents that is applied to wood and other surfaces. It enhances the natural grain and protects from environmental damage like water, abrasion, and UV rays. There are different types of varnishes classified by their resin and solvent composition, including oil, spirit, turpentine and water varnishes. A good varnish dries quickly to a hard, durable and weather-resistant film without cracking or hiding the wood grain. Common ingredients are resins like copal and shellac, solvents like linseed oil, turpentine and alcohol, and metallic driers that accelerate the drying process.

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2. What is Varnish?
 Varnish is a solution of resin or resinous
substances (such as common resin, amber,
copal, shellac etc) in alcohol, turpentine or
oil.
 It enhances and gives warmth to the grain
of the wood and is resistant to impact, heat,
abrasion, water, and alcohol.
It can be used
as a topcoat over
worn finishes.

3. Why varnishing is done?
 To intensify or brighten the appearance of
natural grains in wood.
 To render brilliancy to the painted surface.
 To protect painted surface from atmospheric
action.
 To protect unpainted wooden
surfaces of doors, windows,
roof trusses, floors etc from
atmospheric action.

4. Surface preparation Knotting Stopping Coat of Varnish
The wood
surface is
made smooth
by rubbing it
using sand
paper or
pumice stone.
It is the
process of
covering or
killing all
knots in the
wood work
with a
substance
through which
the resin
cannot come
out or exude
since the
resin coming
out the knots
would
damage the
paint
It is done by
means of hot
weak glue
size so that
pores on the
surface are
filled up.
• Boiled
linseed oil
can be
applied in 2
coats .
• The dry
surface
should then
be rubbed
down with
On the clean
surface, two
or more coats
of varnish is
applied.
• The next
coat is
applied
when the
previous
coat has
dried up
thoroughly.
PROCESS OF VARNISHING

5. Characteristics of a good varnish
 It should dry rapidly
 It should form a hard film on drying.
 It should not crack on drying. It should have
sufficient elasticity.
 It should be durable and weather resistant.
 It should give uniform and pleasing appearance.
 It should not hide the natural
grain of the inner surface of
timber.
 The colour of Varnish should
not fade away with time.

6. Properties
 transparent
 hard
 protective finish
 It is combination of a drying oil, a resin, and
a thinner or solvent.
 glossy but may be designed to produce satin
or semi-gloss sheens by the addition of
"flatting" agents.

7. Ingredients of Varnish
 Driers
 Resins or resinous
substances
 Solvents
DRIERS
Driers accelerate the process of drying of a
varnish. Common driers used in varnishes are
litharge, white copper and lead acetate.

8. ALKYD- TYPE OF DRYER
 Typically, modern commercially produced
varnishes employ some form of alkyd for
producing a protective film. Alkyds are
chemically modified vegetable oils which
operate well in a wide range of conditions
and can be engineered to speed up the
cure rate and thus harden faster.

9. RESINS OR RESINOUS SUBSTANCES
 The quality of resin depends largely on the type
of resin used.
 Various types of resins in use are copal, resin,
shellac, amber, mastic, gum dammar etc
 Copal is a hard and lustrous resin
obtained from ground where pine
trees existed in past.
 Resin is obtained from pine trees.
 shellac is obtained by exudation of
some insects which grow on some
type of trees in India.

10. SOLVENTS
 Boiled linseed oil
 Methylated sprit
of wine
 Turpentine
 Wood naphtha
 Amber, copal
 Shellac or lac
 Mastic, gum
dammar
 Raw copal and
other cheap
varieties of resin
Type of
solvent
Type of resin

11. Classification of varnishes
 Varnishes may be divided into the
following four categories based on the
type of solvent used:
1. OIL VARNISHES:
these varnishes use linseed oil as
solvent in which hard resins such
as amber and copal are dissolved
by heating. These varnishes dry
slowly, but form hard and durable
surface. Recommended for all
external wood work and for joinery,
fittings.

12. 2. SPIRIT VARNISHES OR LAQUERS:
These varnishes have methylated spirit of wine
as solvent in which soft resins such as
shellac are dissolved.
They dry quickly but are not
durable.
French polish is a variety of this
type of varnish.
it is commonly used on furniture.

13. 3. TERPENTINE VARNISHES:
These varnishes use
turpentine as solvent in
which soft resins such
as gum dammar, mastic and
rosin are dissolved.
They dry quickly but not
so durable.
These are cheaper than
oil varnishes.

14. 4. WATER VARNISHES:
These varnishes are formed by dissolving
shellac in hot water, using enough
quantity of either ammonia,
borax, potash or soda.
They are used for varnishing
wall papers, maps, pictures,
book jackets etc

15. Types of varnishes
POLYURETHANE:
varnishes are typically hard, abrasion-resistant,
and durable coatings.
 They are popular for hardwood floors but are
considered by some wood finishers to be
difficult or unsuitable for finishing furniture or
other detailed pieces.

16. ACRYLIC VARNISHES
 Acrylic varnishes are typically water-borne
varnishes with the lowest refractive index of
all finishes. Empty citation (help) and high
transparency. They resist yellowing. Acrylics
have the advantage of water clean-up

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