This section is from the book "Cyclopedia Of Painting", by George D. Armstrong. Also available from Amazon: Cyclopedia of Painting.
In repainting an old surface, it is especially important that the contractor consult a practical painter. Carefully examine the surface to he painted before commencing the work and determine whether there is any loose paint or whether the undercoat is in condition to break loose as soon as an elastic coat is applied over it. If the building has previously been primed with ochre, watch out for spots that have received a heavy coat and are ready to break loose. Examine the surface for dampness from basements, drain pipes, down spouts and wet soil. Before starting to paint, see that dampness has not undermined the paint and that the boards do not contain enough moisture to cause the paint to break loose as soon as other coats are applied over them. Look out for loose scales, fine or powdered. They do not appear to be dangerous, nevertheless, they will keep the paint from adhering solidly to the surface and make it soon break away. Be careful about mildew, as this condition is always a sure sign of dampness, and paint applied over mildew will soon spot or peel. Examine the surface to see whether the paint of previous coatings has shriveled. Paint applied over a shriveled undercoating will soon break loose.
Prepare the paint according to the surface over which it is to be applied.
When the surface to be repainted is in good condition and not cracked or peeled, thoroughly clean the building free from dust, dirt or soot. Wash mildewed spots with turpentine. It is seldom that one mix of paint will answer for all parts of the building. Portions of the house that are the most exposed and weather-beaten should receive the most elastic coat of paint. Portions that are protected, like under porches and verandas, and portions shielded by trees and other buildings, which would render them in about the same condition as under verandas, should receive a coat of paint mixed so as to penetrate the old surface and dry hard and firm without high gloss. If one mix of paint, which will satisfy the exposed portion of the building, is applied over the entire surface and to the protected or hard parts of the building, this oily or elastic coat of paint will dry with a full or heavy gloss, retarding the drying of the second or finishing coat, also causing blistering, checking, cracking and flatting in a short time.
For an exposed or weather-beaten surface, the paint should be mixed with 2-3 oil and 1-3 turpentine to assist in penetrating the old surface, as well as parts on which some paint still remains. It should be applied with a full brush to fully satisfy the surface and be well and evenly brushed out so as not to have an excess of paint on the surface where the old paint remains.
The cornices and protected portions should receive paint that is mixed half flat or with enough turpentine to force penetration through the old paint, thus firmly binding this coat to the surface and preventing the second or finishing coat from crawling. The paint should be applied smoothly and evenly and be well brushed in. Do not flow the paint on and expect a uniform coat.
When the surface is thoroughly hard, putty all cracks, seams and nail holes, knifing the putty well in. One mix of paint for finishing coat can be applied over the entire surface. This will dry uniformly. The paint should be mixed to medium heavy and elastic consistency and be well and evenly brushed out.