Waterproof long oil varnishes should not be applied to furniture, because they dry too slowly, are too soft, lack high luster, and do not rub well.
Furniture finishers prefer short oil varnishes because they dry hard and quickly and have a brilliant luster.
The wood finisher's problem at first is the selection of a suitable varnish.
The experienced wood finisher is particular about the brush or brushes used in spreading varnish.
A brush of the proper size, with well set bristles of medium stiffness, should be selected.
Either flat or oval-shaped brushes may be used.
Oval brushes are preferred for large, surfaces where big brushfuls of varnish are necessary for rapid work.
An old brush which has been used with paint or shellac is unsatisfactory.
Even a high grade new brush, "set in rubber," requires preliminary treatment before it is ready for use on a last coat job of varnishing.
A new brush should have the dust and loose bristles removed before it is fit for varnishing any type of wood surface, whether it is frieze boards, bar rail moulding, or wood frames.
It is best to use a new brush for undercoat work for a while, until all loose bristles are removed or fall out.
Then, after a careful cleaning in turpentine, it is ready for finishing work.
All surfaces should be examined to find out whether they are properly dry before varnishing is begun.
Trouble is almost sure to follow if you apply a second coat of finish over a partly dried undercoat.
Dusting and cleaning the object to be varnished just before varnishing is begun are very important operations that the amateur may overlook.
Dust is continually settling and should be removed just before spreading the varnish.
If there is much dust on a piece of furniture or some other object which is to be varnished, it is preferable to take the article away from the varnish room for dusting, in order to avoid scattering dust into the air of the finishing room because some of it is very apt to settle on a newly varnished surface and spoil the finish, especially on a piece of specialty wood for fireplace designs, designer window toppers, or bar rail moulding.
After removing the loose dust with a dusting brush, the surfaces should be wiped with a piece of cheesecloth or chamois skin dampened with water.
A piece of muslin or cheesecloth may be dampened with benzine or turpentine for cleaning a surface which has an undercoat on it, or a "tack-rag" may be made by dampening a dustless and lint- less rag in very thin varnish.
Such a "tack-rag" if nearly dry, will take up all dust and leave a surface ready for varnishing.
All fragments of sand and dust must be removed from the cracks, corners, and pockets in the cells of the wood, or these waste particles will be dragged out by the brush in flowing on the varnish and will spoil an otherwise perfect finished set of designer window toppers, wood corner blocks, or frieze boards.
Old surfaces which are to be re-varnished should be washed thoroughly with moderately strong soapy water, then rinsed and wiped, preferably with a chamois skin dampened in clear water.
After washing and drying, all old varnished surfaces should be smoothed down with fine sandpaper which also removes the gloss.
Then they should be carefully dusted and wiped to make them clean and dustless.
Old wax finishes, or surfaces that have been treated with a varnish remover containing wax, should be cleaned properly with benzine, turpentine, or even high-test gasoline.
Such surfaces should be wiped, after treatment with the waxsolvents, in order to remove all traces of wax.
New films of varnish will not adhere satisfactorily to surfaces having even a small amount or a very thin layer of wax on them.
The finishing room and the wood finisher`s clothes should be as free from dust as possible.
Sometimes the floors in finishing rooms are sprinkled with water to lay the dust.
The rooms should be dry, however, because varnish does not dry well on damp days.
When the weather is damp or rainy the windows should be closed.
Ventilation without drafts is desirable because fresh air helps oxidation of the drying oils in the varnish, and speeds up the evaporation of the solvents and thinners.
The temperature of a varnishing-room during the winter time should be between 70° F.
and 80° F.
, and certainly never below 60° F.
, because warm varnish spreads more satisfactorily.
If varnish has been seriously chilled by exposure to very cold weather, it should be warmed by placing the container in warm water, and finally strained, particularly if it is not properly mixed or has separated into its original ingredients to some extent.
Varnish should not be thinned by the finisher, because the manufacturers put as much thinner in the mixture as it will stand and still give satisfactory service.
If you need a thinner varnish, you can place the container in warm water or add a small amount of turpentine.
If thinner is added to a varnish, you should wait at least twelve hours so that the ingredients may become properly mixed.