The paint should frequently he stirred up in the pots. The pigment, being heavy, has a tend ency to settle to the bottom, and unless it is kept in suspension by frequent stirring the house will be streaky.
Covering Knots. It is essential for the dura bility of the paint that all knots or sappy places in the wood shall be coated with some material which will seal up the resinous matter within the wood and prevent it from causing blisters or otherwise destroying the paint. The best material known for the purpose is pure orange shellac. This is better than bleached shellac, since the latter has lost much of its strength owing to the chemicals employed in bleaching. A wood alcohol shellac, although inferior to one made by dissolving the shellac in grain alcohol, is good enough for cover ing these knots and sappy places. It is the practice of some painters to shellac knots be fore priming, but other experienced painters maintain that better results are obtained by priming first. It is therefore well for the archi tect and builder, in a matter of this kind, to defer to the judgment of the painter, insisting only that all knots and sappy places should be well coated with shellac. One reason advanced for shellacking after priming is that the shellac is better protected from the action of moisture which may penetrate through the boards, shellac being very susceptible to moisture.
Care in Spreading Priming. As many paint ers are careless about the quality of the material they use for priming, so they are equally indif ferent to the workmanship that is used in spreading it. There is no excuse for the care less workman who slaps on the paint in a hit or-miss fashion, brushing it on in any direction just so that the wood will be covered. It takes little if any more time for the painter to apply the paint smoothly and evenly, avoiding brush marks; if these are left on the priming coat, they will show through the subsequent coats.
The priming should be well brushed out and rubbed into the grain of the wood. Unfor tunately it has become common to use a wide (four-inch) wall brush for outside painting, be cause the men can cover a greater space in a given time. The journeymen prefer this kind
of brush because less exertion is required; but there is no doubt that better and more durable painting will be accomplished where the paint ers use the old-fashioned round brush known as the "pound brush." There is more spring to the bristles of this kind of brush, and when used properly it will work the paint into the wood most effectively.
Why Thin Coats Are Best. Paints should always be applied in thin coats well brushed out. No greater mistake can be made than the usz, of heavy coats of paint, although it is the cus tom of many architects to specify "good heavy coats." Heavy coats almost invariably cause blistering or wrinkling of the paint skin, and will not last as long as thinner coats. The old practice of making the priming coat thin, and then following it up with two or more coats of paint mixed moderately stout and well brushed out till they were thin on the surface, largely accounted for the durability of the painting of a generation ago. Three thin coats of paint will give fifty per cent more wear than two heavy coats, although less material is used in the three coats.
Using Putty. All cracks and nail-holes must be thoroughly filled with putty, in order to make a firm and solid foundation for the subse quent coats of paint. This puttying is usually done after the priming, but some painters pre fer to putty before priming, claiming that bet ter results are obtained. The putty should be made from the best grade of bolted whiting, mixed with pure raw linseed oil. Very little pure putty is sold commercially, and much trouble results from the use of putty made from marble dust and kerosene or containing these materials. The saving effected on a house by the use of cheap putty is so slight that the pure should always be insisted on.
Some painters make their own putty by mix ing the whiting and oil together in very much the same way as bread dough is kneaded. Although such putty may cost a little more, it will not shrink and fall out like the cheap putty, nor will it discolor the paint that is applied over it.