Two grades of varnishes will usually be required by the painter, inside and outside. That which is used outside will cost a little more than that intended for the interior, as it must be made of materials to resist the weather. If the color of the work is dark, oak varnish is the best to use, but there are various grades of pale varnishes suitable for very light work, some can be obtained which have very little color at all. A special grade of varnish is made for application to wall paper, this, however, is a common grade of varnish, and is not recommended. It is much better to pay a little more and get a good copal varnish. Before paper is varnished it is necessary to give it two coats of size. Concentrated size powder may be used for the purpose, two coats are necessary, so as to ensure no portion of the work being missed. If this is not done the varnish will soak in the paper and leave a nasty black mark.
As a rule, a paper wall should not be varnished. The distempered surface of an ordinary paper looks much better, and it may be kept quite clean if it is frequently brushed down lightly. Dadoes are used in halls and staircases because they assist in giving a finished effect to what would otherwise have a mere bare appearance, and also because when varnished they prevent soiling of the paper by dirty hands. The dado is twice sized, care being taken to apply the size a little above the edge of the dado, so as to prevent the varnish running.
The application of the varnish to either paper or wood work requires some care. The painter is apt to try to get over the work too quickly by taking too much in his brush at once, and this is certain to lead to nasty running or tears. The best way is to dip a little more than the tip of the brush into the varnish, to apply it almost in the same manner as paint across the work, and then to finish by lightly stroking the surface all in the same direction with the tip of the brush, so that the varnish flows and the brush marks are obliterated. Special brushes are required for varnishing, and it is useless to attempt to do good work of this character with an ordinary paint brush. There is no economy in buying a cheap varnish brush. The work done with one is very likely to be marred by the bristles coming out, and such tools only last a comparatively short time. A varnish brush when put aside for a day should be put in either raw linseed oil, or, better still, in some of the same varnish in which it has been used. It should be suspended and on no account to be left to rest upon its bristles.
When not required for further use for some time it should be washed out first with raw linseed oil, and then with turpentine, and then wrapped in paper and put away in a cool dry place.