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Emulsion Painting Practice

Preparing the Surface
Methods of Application
Cleaning Brushes and Equipment After Use

By Ray Lewhite.

In recent years plastic emulsion paints have been added to the ever-growing range of decorative materials available to the home decorator. These emulsion paints possess properties which instantly appeal to the amateur and have, therefore, provided a further stimulus to the do-it-your self world. However, as is the case of the older established types of decorative paints, it is essential to fully recognise there particular properties and features in order to ensure the most successful results.
In the first place what are these plastic emulsion paints? The dictionary defines an emulsion as a milky liquid having oily or resinous particles in suspension which ordinarily will not mix.
In the case of the majority of emulsion paints offered for sale in the retail shops these are based on polyvinyl acetate derived from vinyl resins, and are known as P.V.A. paints. From the emulsion in water base, which is the binder for the paint, various additives such as thickening, dispersing and stabilising agents are added together with a plasticiser to impart flexibility. The necessary high strength colouring pigments are selected for there alkali-resistant properties.

Quick Drying Properties

Painting with Emulsion
Apart from the ease of application, the rapid drying is probably the outstanding feature of these emulsion paints, as time is usually an important factor in home decoration. The absence of objectionable odours and inflammable fumes is also greatly appreciated. Emulsion paints dry by the evaporation of the water content and this feature ensures that under average warm and dry conditions, a second coat may be applied within one or two hours of the first. This fact substantiates the manufacturers that a room can be redecorated in a single day, so far as the preparation and treatment of the ceiling and wall surfaces are concerned
When thoroughly dry and hard over a period of time emulsion painted surfaces can be washed with soap and water or a mild aqueous detergent solution, sugar soap etc., to remove finger marks and accumulated grime and to restore the original newly painted appearance.

Preparing the surface

Painting with Emulsion
It should be recognised that emulsion paints do not posses outstanding properties of penetration to bind down existing wall coatings such as distempers and the like which may be in an advanced state of flaking, powdering and general disintegration. In such a case it becomes important to remove all traces of unsound or loosely adherent material by washing down, using a scraper or soft wire brush. If complete removal is not altogether possible, it is often advisable to first apply a sealer coat of an orthodox paint to act in this capacity and provide a base the emulsion paint when dry. Most retail shops offer such a material which is usually described as a plaster sealer or primer.
In common with other types of decorative materials, emulsion paints have very limited tolerance to grease and dirt, and washing down in the usual manner is required prior to application.
The low penetrative power means that some form of mechanical grip or "key" must be made by rubbing down with sandpaper on for example, a hard gloss painted surface if the conditions are such that concentrations of moisture are likely to be subsequently present as in bathrooms and kitchens. The reason for this becomes apparent when it is recognized that emulsion paints have some affinity to water and may tend to swell by absorption of moisture. The alternate swelling and shrinking as room conditions change may occur to an extent which is sufficient to detach the coating from the underlying paint in the form of flaking.
This occurs particularly if the bond or force of adhesion between the two is weak, because the hard gloss paint coating itself forms a barrier which does not permit the moisture to penetrate any further. In these circumstances and under severe conditions it is generally advisable to use conventional gloss paints to avoid the risk of failure.

Methods of Application

Painting with Emulsion
The water content of emulsion paints normally precludes their use on ferrous metal surfaces in that rusting may be promoted unless a suitable rust suppressing primer is first applied. To apply emulsion paints direct to wood may also be a dangerous in that water is introduced to the wood and again a suitable primer is first required. Application in very damp atmospheric conditions is also not advisable in that the normal drying rate is considerably retarded and this may be somewhat detrimental to the film.
On the other hand, emulsion paints are particularly suitable for application to newly plastered and cement rendered surfaces in that the waiting period before decoration can be applied is greatly reduced compared to that required for gloss paints on conventional media; the slightly porous or permeable nature of the emulsion paint allows the wall to breathe and subsequently dry out through the film. The inert nature of the resin and the absence of drying oils, such as linseed oil, obviates failure due to the formation of soapy-like deposits on the film, resulting with reaction with the alkaline salts of the plaster or cement.
The slightly porous nature of the coating also completely minimises failure due to efflorescence, a powdery eruption of the coating due to the crystallisation of salts brought forward, to the extent that this will not occur sufficiently to weaken the adhesion of the coating. The efflorescence generally occurs on top of the coating and can be brushed-off without injury. However, this does not mean emulsion paints can be applied almost immediately to newly plastered walls, as it still becomes important to allow a reasonable interval of time for the excess moisture to dry out, otherwise this moisture will tend to repel the emulsion coating and may result in very poor adhesion.
Wetting the wall and observing the speed of which the wetness disappears can provide a rough guide to the condition of the plaster. It should be noted that emulsion paints have valuable mould-resistant properties and can be considered as fungi-resistant.


Painting with Emulsion
As stated, emulsion paints have great ease of application and may be applied by brush, roller or spray. For brushing, emulsion large emulsion flat brushes are commonly used. All types of home decorators rollers, lambswool, nylon, etc. are suitable. The lightweight portable types of spray equipment can also be used. When brushing the emulsion paint is best applied without prolonged brushing out; that is to say applied in a criss-cross manner and not laid-off vertically from ceiling to floor as in normal painting practice. The virtual absence of brush marks on drying out is a particularly pleasing feature. Most emulsion paints are applied un-thinned, except in special circumstances such as on very porous surfaces in which case the emulsion paint may be thinned only sufficiently to overcome the drag on the brush caused by this absorption; over-thinning of course, reduces the opacity.
Painting with Emulsion
Using the small capacity spray plants, thinning is often necessary in order to provide a smooth wet coating, but again the minimum of thinners should be used. Manufacturers of emulsion paints market a suitable type of thinners, and whilst water only can be used this almost invariably reduces the sheen of the finish and lessens the wearing properties.
Normally, emulsion paints dry a slight satin finish sheen with a slightly textured surface in the case of roller and spray applications. The degree of sheen can be increased if required by adding a percentage of the emulsion glaze which is marketed for the purpose, rather like adding more varnish to a normal type of semi-matt paint. This transparent P.V.A. glaze has also a novel use as a protective film over wallpapers to render them washable.
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Special Paint Finishes.