Marine Spar Varnish and Brightwork. The varnished wood on many boats is referred
to as "Bightwork". You can have just a few pieces of brightwork such as hand rails, toe rails, transom or your whole
boat can be finished brite. Doing the brightwork on a entire boat can be quite time consuming and may require extensive
periodic maintenance but for the do-it-yourself persons can be a great source of pride.
There are three primary types of varnish, alkyd, polyurethane, and two part.
The alkyd varnishes are made from a base of natural oils such as linseed or tung oil. These varnishes can
also be a blend of the two oils. With the addition of UV asorbents or reflectants the alkyd marine spar varnish can
have a very high gloss, flexibility and good surface hardness, as well as water and weather resistance. Most marine spar varnishes
are made from these bases.
Polyurethane varnishes are made from a polyurethane oil base. Originally these
varnishes had a more plastic finish which had very high flexibility and high abrasion resistance. These varnishes did
not contain UV inhibitors and were mainly used for interior finishes and flooring.
Two part varnishes refers to the newer types of clear finishes requiring a base and
a hardener to be mixed. Often these are Linear Polyurethanes and they have a extremely agressive solvent nature that
prohibits their use over existing varnish or one part enamels. They have extremely high UV resistance and abrasion resistance
due to their surface hardness. However, in our experience they are somewhat lacking in flexibility which may lead to
cracking when coated over a bare wood substrate. These are best used when a epoxy primer surface has been applied to
wood first. Lastly, in the event of damage to the wood, these two part systems can be very hard to make invisible repairs.
Here at Classic Craft we continuously test varnish in the outdoor enviroment to see how well
they are holding up. We compare our own tests with testing done by others, such as the Practical Sailor Periodical,
to verify that we are using and recommending the finest finishes available.
Application is pretty straight forward. We do not recommend the over thinning of varnish
as some persons do. Wood is much like a mesh screen in that it will pass certain size molecules and not others.
Remember a wine barrel passes very little water over great periods of time and that the water molecule is one of the smallest
and most universal solvents there is. So why would anyone expect large molecule solvents and thinners to penetrate the
wood any deeper. Also, excess thinning can lead to solvent entrapment under the surface dried varnish and later bleed
back into the varnish attacking it. Follow the manufactures directions on thinning they really want you to have good
results with their product and they will not steer you wrong.
We thin our first coat of varnish 10% and subsequent coats are never thinned. Applying
varnish this way will lead to quicker surface build and less porosity in the final varnish film. If you are applying
in cool weather we recommend heating your project to a minimum of 55 degrees farenheit and also placing the varnish in a pan
of hot water to warm it.
In really hot climates the varnish may dry to fast not allowing for a proper flow out.
At this time you may want to add a retarded to increase drying times. We like to use the Penetrol product for this purpose
or a very small quantity of boiled linseed oil.