< OIL PAINTS
MODERN COMMERCIAL PAINTS
Modern commercial paints are generally highly evolved and extensively tested coatings. In their various guises, modern paint products offer the user a vast range of finish options (flat, matt, gloss, luminous, textured. pearlescent and so on). By the same token, types of compatable primer and finish paints are available for application to a wide range of materials, and for most conceivable situations. Suitable paints for sculpture include high performance polyester and polyurethane TWO PACK paints (a paint body with separate hardener and a matching thinners), this type is exceptional for coating works exposed to potentially extreme environments. Paint coatings can be applied to metallic surfaces by various techniques including brush, roller and spray diffuser. There are too many paints and finishes for metalworks to be practically listed here; however, there are a number of common factors concerning the use of paints on cast (or wrought) metalworks.
Any selected paint should be purchased in sufficient quantities to enable the total surface area of the work to be completed from a single consignment (especially the case if a paint is ordered to a unique specification). Where possible, use paints which carry either a BSEN, ASTM, RAL [ref], or other colour reference standard. It is also important to ensure that the paint selected is suitable for the environment in which the coated work is to be eventually situated. Both interior and exterior locations can, in their own separate ways adversely affect a paint finish, either through the action of wind, rain, heat, vandalism, or the loss of colour fastness under prolonged exposure to ultra violet light.
A further consideration when painting metal artworks, is the potential for an adverse reaction to arise between the compounds present in the paint, and those of the cast alloy. Incompatible paint and metal interactions can lead to discolouration or loss of adhesion. Such incidents can be prevented by the careful selection of a suitable paint and following the correct preparation of surfaces before applying a suitable primer paint or other barrier coating. Appropriate surface conditioning of the cast work (SHOT BLASTING or ETCHING for instance), and the correct primer treatment, may vary according to the specific alloy used for the cast, and the chemical composition of the paint finish. Details and advice on paint compositions and compatibility can usually be obtained from the paint product’s manufacturer (if this information is not already on supplied packaging or data sheets). When consulting a manufacturer on the appropriate preparations for a paint product, it is best to have to hand details of the proposed cast’s ALLOY composition. This information is normally available in the form of a detailed ANALYSIS or CONFORMITY CERTIFICATE, information which can be obtained from the founder via their metal ingot supplier (see SUPPLEMENT).
Metal surfaces for painting should be clean and free of loose particulate, grease, oil, and moisture. Any undercoating or primer coating must be fully dried and allowed to harden, unless otherwise directed. Throughout application, care should be taken to avoid obvious brush marks, runs, ‘curtains’ and the collection of paint in pools. More complicated cast forms and textured surfaces may be better suited to spray painting, with the aid of a compressor and diffuser system. Where protective paint finishes are specified for corrosion prevention, it is essential that both the engineer’s specifications and the manufacturer’s instructions are followed carefully to ensure that maximum protection is imparted to the structure. For corrosion protection, a HIGH BUILD BITUMIN paint (bitumen carried in a hydrocarbon solvent), applied over a shot-blasted steel structure primed with a ZINC ALKYD primer, makes an excellent hand painted alternative to a HOT DIP GALVANISING.
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