Varnishes are liquid coatings containing a resin dissolved in an oil or solvent that form a protective film. They are used as decorative and protective coatings on wood and painted surfaces. The key ingredients are a resin such as rosin, copal or shellac dissolved in a solvent like linseed oil, turpentine or spirits. Different types of varnishes are used depending on the solvent - oil varnishes dry slowly but are durable, turpentine varnishes dry quickly but are less durable, and spirit varnishes containing shellac are commonly used for furniture. Japans contain asphalt and are applied to metal surfaces. Varnishes protect surfaces from moisture damage and weathering while enhancing the natural

1. Varnishes
Building Construction Material

2. Definition
• A Varnish may be defined as a
“homogeneous liquid Containing essentially
a resinous substance dissolved in a suitable
oil or a volatile liquid”. A Varnish does not
contain any pigment. However it is always
used as a finishing coat.

3. Varnish

4. Function of Varnish
• More Commonly a Varnish is used over a
wooden object as a decorative & Protective
Covering.
• The Varnish brings out the grains of wood in a
brilliant manner when given without a paint.
• On the painted surface, varnish imparts a
delicate brilliance.
• Moreover, the resinous material dissolved in the
varnish forms a thin film on the drying which
protects the surface below from deterioration to
moisture.

5. Function of Varnish

6. Ingredients of Varnish
• The two essential component of varnish are a
base or resinous substance and a solvent. The
resin of varnish may be natural or artificial.
Natural resin used in varnish are rosin, copal,
shellac, amber, and dammar. Synthetic resin
include phenyl, and vinyl resins.
• The main solvent used in varnish are boiled
linseed oil , turpentine, and methylated spirits.
Water has also be used in some special varnishes.

7. Natural Resins

8. Artificial Resins

9. Rosin

10. Copal

11. Shellac

12. Amber

13. Dammar

14. Solvent Used In Varnish

15. Type of Varnishes
• Some common types of varnishes distinguished
on the basis of the solvent of constituents are as
follows:
Oil Varnish
• Those Varnish in which linseed oil has been
used as a solvent form this group. The base
material may be amber or copal. Although they
dry slowly, they form a hard and durable film.
Hence they are popular for use in external finish.
They are quite resistant to weather changes.

16. Oil Varnish

17. Type of Varnishes
Turpentine Varnish
• These are made by dissolving gum, mastic
or rosin in turpentine. They have the
advantage that they dry quickly. At the same
time, the film formed is neither much
durable nor resistant to moisture. Hence
they are used only in interior work.

18. Turpentine Varnish

19. Type of Varnishes
Spirit Varnishes
• They are commonly used varnish for
furnitures. They consist of Shellac dissolved in
methylated spirits. French Polish is a varnish
belonging to this group.
• Sometimes a small quantity of a pigment is also
added to give a desired shade to the finish. The
spirit varnish are also not much durable. They
are also not resistant to weather changes. Hence
these can be given only on wooden articles
protected from rain, gases and light.

20. Spirit Varnishes

21. Type of Varnishes
Japans
• These are a class of varnishes that have asphalt
as an Important ingredients. Asphalt is
dissolved in a linseed oil in the presence of a
volatile thinner.
• JAPANS are applied mostly to metal surfaces.
The surface is first- given a coat of JAPANS
and then heated to baking temperature at 210 0 C
for few hours. On Cooling, the paint forms a
coating that is highly resistant to chemical
corrosion.

22. Japans

23. References
• Building Construction : Dr B.C. Punmia
• Civil Engineering Material : Prof. Singh
• Internet Web Sites

24. Thanks…