Repainting work provides a set of problems quite apart from those occurring in working over new or burnt off surfaces. It is important that these major differences are appreciated if successful retreating of the surfaces is to be achieved. A large proportion of old paint work does not require burning off or house paint removal prior. It is, however, necessary to ensure that the ground is prepared thoroughly in other ways in order to obtain good results.
With favorable conditions, including careful preparation of the surface and the use of suitable paint combinations over a period of years, burning off may be entirely avoided. Much depends upon repainting being carried out at regular intervals, without allowing the paint to deteriorate beyond a reasonable degree.
Where the old paint is firmly adhering to the surface, it provides a satisfactory ground for further paint application.
Repainting requires less work in many ways, because the surface suction has been satisfied, and two coats only are required to give a good serviceable finish. However, in spite of this advantage, a far greater skill and knowledge is necessary to successfully carry out house paint removal. It is necessary to consider the amount of weathering the surfaces will have and, in addition to this, the new paint and treatment must be selected to provide a paint finish which is of similar composition and qualities to the old paint on the surface. Lack of unity or affinity between the new material and the old work will inevitably lead to faults developing in the work through an uneven tension between the various layers of the film. Poor adhesion is also likely to result under these circumstances. It becomes apparent, then, when purchasing new materials for use over old paint work that greater consideration should be given to the characteristics and qualities of the old material in order to select a similar type of material and, if possible, the same brand as that which was used previously. By this means, uniformity of tension will be maintained through the depth of the coatings.
Home Interior Decorating – Preparation of Old Painted Surfaces
Interior house painting tips for the interior of your home
Although washing down is not always necessary, particularly when exterior house painting, it will be an advantage to do this. The removal of paint and dust will allow a smoother and cleaner paint finish and ensure against any new fault developing. A cleaning solution of washing soda and water will be ideal for removing dirt and other impurities, and it can be in no way detrimental when home interior decorating. When washed down, the surface should be swilled off with fresh water and allowed to dry out thoroughly before any paint is applied. Rubbing down is an important process in treating old paint work in order to achieve a smooth surface and to provide a key for the new coatings.
When dry rubbing is carried out, M2 glass paper is usually the grade most suitable for exterior painting. On more particular work, pumice stone or garnet paper may be used in conjunction with the cleaning solution. Exterior house painting is based largely upon the action of preventing moisture from penetrating into a surface, requires careful attention to filling or stopping all holes, cracks and joints. No paint combination will last in a satisfactory condition once unlimited moisture has found a means of penetrating behind the paint film.
To achieve this objective, the stopping should adhere to the edges and walls of the cavities without any shrinking. Linseed oil putty is more durable for exterior oil paint work.
Enamels and lacquers require putties more in character with the particular finishes. These are usually of a harder drying nature than the linseed oil putty. Putties are highly pigmented mixtures which are more absorbent than the old painted surfaces, and require two coats of paint over the top to achieve a uniform nonporous surface coating.
“Sinking in” will occur over putty which has only one coat of paint applied. Linseed oil putty requires a coating the same day that it is applied so as to incorporate the stopping and the paint coating and give a smoother appearance to the work.
Undercoats
The first coat of paint over old work should be an undercoat. These pigmented mixtures are formulated to give better adhesion and to provide a foundation for the finishing gloss coating. Gloss coatings do not adhere to hard, smooth surfaces, and are likely to skin over without actually gaining any sound key. The finely granulated surfaces of the undercoat supply the necessary tooth.
It should be noted that the undercoats, although requiring to be fairly turpentinic mixtures, should not be hard drying or brittle, as this will cause uneven tension during the exposure of the surface.
An old, slightly powdering, painted surface provides the best foundation for the new mixture. The binder in the new undercoat penetrates into the slightly porous surface of the old film, sealing down the loose pigment and binding the two coatings together. In actual practice, however, the various portions of exterior house painting work seldom ever weather, at similar speeds or degrees, and for this reason greater attention is necessary to sanding or cutting down the hard, smooth face of more protected portions of the old paint to provide a roughened surface to which the new material can key. This applies also to the renovating of old enamel and interior painted surfaces and on this work wet rubbing will be found more effective. The undercoat should be rubbed down with F2 glass paper to give a smoother finish. It should be appreciated that the rubbing down of new coatings is only carried out to smooth down any irregularities in the previous coating caused by dust or fine nibs on the surface, or for the elimination of any coarseness through brush marks, etc. As the paint is fresh and only relatively hard, the rubbing should be very lightly done, in order to prevent damage to the paint.
Interior Painting – One Coat Paint Work
One coat paint work is seldom successful when embarking on an interior painting job, although it may be used on metal surfaces such as roofs, spoutings, etc. The uneven weathering of exposed surfaces leads to uneven suction or porosity of the surface coating, with the new material sinking into the powdering sections of the surface. Thus the putty work will also show up in dead patches, because it has received only the one coat. It would be incorrect to say that one coat work is impossible, and indeed there are some occasions when it may be advisable where too many coatings will cause faulting. However, when painting a house interior requires putty, or where the surfaces are not thoroughly rubbed down, trouble will develop.
Materials for Interior House Painting
The different conditions governing wear on interior surfaces in the home call for materials of varying characteristics. In many cases the required qualities are entirely at variance with those required for exterior paint mixtures. Interior finishes, although protected from general weathering, are still open to faulting or damage from other sources. Some consideration should be given to this when selecting the type of material to be used on painting house interior.
Quality Mixtures
Quality is one of the most important factors in the selection of materials when interior house painting. Stinting in this direction will inevitably result in inferior work, and as the possible saving achieved would be relatively small, any risk would not be worth while.
Hand Mixing
Although most materials can be prepared by “hand mixing” by the skilled craftsman, the modern painter is able to purchase materials for any practical decorative use from the paint manufacturer.
Machine made Coatings
The use of these materials, machine processed and finely adjusted under carefully prepared formula, is likely to result in more uniform qualities and less inconvenience on the job.
Limitations
However, it also imposes a degree of restriction, and it will be found advisable to pay particular attention to the manufacturer’s instructions regarding the use and thinning of machine made paints.
Testing
It should be borne in mind that reputable manufacturers market their products only after exhaustive tests, and reasonably good results can be expected providing due care is given to the mixing and preparation of the paint coatings.
Individual Conditions
Each room presents a different set of problems and should be considered on its own merits when painting the house interior.