The West London Railing Company & The Kensington Railing Company are part of TIHH Group of Companies, Supplying: Railing Restoration, Railing Reconditioning and Railing Painting in London, Surrey and the rest of England |
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WESTMINISTER COUNCIL GUIDELINES
8. MAINTENANCE: CLEANING & PAINTINGPainting is the most common and, in the majority of cases, the best protection that can be given to railings, if it is done regularly and effectively.Corrosion begins at breaks in the surface of the protective paint and then spreads beneath it. Paint-work on iron should be maintained annually. Defects should be made good by completely removing the old pain and any rust and then priming and painting before more rust is formed. Painting over rust is a waste of money and time. It will not only stain and flake away quickly but it will also attract corrosion and help it spread, by trapping moisture under the cracked surface. Ironwork which is coated with many layers of paint will lose much of its crispness and detail. Especially if the old paint is defective, it is sensible to remove and replace it. Cast iron and wrought iron require different methods of cleaning. A test area which includes the various types of metal and different types of detailing, should be selected and the cleaning method(s) demonstrated on this, so that the correct variables for the job can be determined. The use of experienced operatives is essential. - Click here to contact us 8.1 SURFACE PREPARATION AND CLEANING METHODSCorrect surface preparations is probably the most important single factor in the success or failure of a painting operation. Even the best paints may fail on a badly prepared surface, whilst the simplest and cheapest paint may perform well if the surface is correctly prepared. Good surface preparation is essential for good adhesion which, in turn, will provide a satisfactory appearance and an effective protection to the old railings.The preparation of a sound surface for painting will involve one or more of the following: Removal of old paint; Removal of rust; Removal of loose metal flats or 'mill-scale'; Removal of soluble salts, solidified atmospheric dust and other substances. (Each of these processes requires special knowledge and methods.) 8.1.1 REMOVAL OF OLD PAINTAll paint is loose, perished or flaking, will be removed. It may not be necessary to remove all previous paint coatings, if they are sound, hard and firmly attached to the metal (provided they do no hide important detailing of the ironwork, and they do not make the texture of the material 'lumpy' or 'spotty' in some areas).Small areas of paint may be removed with paint strippers. Their residues will be removed by white spirit or water, as appropriate. Flame cleaning and hot air blowers are also used as they are effective paint removers. It must be remembered that paint removal may reveal cracks, corrosion and casting defects which were not previously visible. Allowance should therefore be made at the outset for dealing with these problems. 8.1.2 REMOVAL OF 'MILL SCALE' FROM WROUGHT IRON AND STEEL'Mill scale' is formed on wrought iron and steel railings, as the result of the hot rolling process and their manufacturing. As the sections leave the mill rolls, they cool and the surface oxidises, producing 'mill scale' (a non-metallic, brittle surface which is easily damaged and tends to detach from the underlying metal). Rust can form at the break in the scale and can spread between it and the metal. Loose or defective 'mill scale' will be removed (sound, adherent mill scale is thought to give corrosive protection towrought iron). Generally, mill scale can be removed by abrasive action, helped, if necessary by application of heat. 8.1.3 REMOVAL OF RUSTRust is an unsatisfactory base for paint and will be removed before any of the new coats are applied. Rust which remains provides a source of further corrosion beneath new paint surfaces. Very small amounts of rust can normally be cleaned with abrasive action and can be treated with a chemical rust converter. Deeper affected patches of metal may need to be repaired with metal fillers after cleaning and treatment. In more severe cases, the affected part of the metal may have to be removed and replaced.8.1.4 REMOVAL OF OTHER FOREIGN SUBSTANCESAny other foreign substances, such as soluble corrosion salts, grease or solidified atmospheric dust are undesirable and should be removed. Such substances may be firmly embedded on old railings and not be easily removable by simple wash; targeted local abrasive cleaning or the use of hot water with detergents and other mild chemicals may often be necessary. 8.1.5. CHOOSING THE RIGHT CLEANING METHODCleaning of old painting from railings can be done with different methods, depending on the type of the metal, the actual design and detailing on the parts and sections and very significantly, on the condition of the railings.In ordinary cases, cleaning of metalwork before painting can be achieved satisfactorily by manually applied abrasion.Manual cleaning allows good targeting of action and less risk of accidental damage of the metal. In cases of very extensive cleaning projects or railings of complex design, or defective ironwork, one or more of the following methods will be employed: * Mechanical cleaning - * Dry air-abrasive cleaning - * Wet abrasive cleaning -* Flame cleaning - * Chemical cleaningIf a set of railings can be dismantled, it can be immersed in a bath of acid, which can remove paint rust and scale. This chemical method is known as 'acid pickling'. It can be very effective but it is recommended that the dismantled parts are taken away and treated in the workshop where the cleaning process can be carefully controlled. The main advantage of the chemical cleaning methods is that, if they are undertaken by experienced specialists, they can be highly effective and adaptable to specific requirements.Special attention is drawn to the fact that these methods use concentrations of chemicals which are potentially dangerous to health and can easily damage the skin and most surfaces on accidental contact. Cleaning, especially the removal of thick layers of old paint, may reveal minor cracks in the ironwork, or other damage that was invisible before. Such damage will be repaired properly; a thorough inspection of the cleaned ironwork is necessary before any preparatory coatings or paint is applied on the metal.8.2. ADDITIONAL MEASURES OF PROTECTIONTraditionally, thoroughly cleaned and dried ironwork is ready to receive priming, undercoating and finishing coats of paint. Extra protection can be given by additional treatments, which are sometimes applied to new ironwork but can also be done to cleaned old railings. Methods of extra protection generally provide a metal coating (a simple process known as spray-metal-coating) or a series of protective alloy layers bonded chemically to the surface of the metal (hot dip galvanising). These can reduce the need formaintenance and increase the useful life of the ironwork. They should never be undertaken without expert advice; maintenance of ironwork treated with these methods may require special primers and paints. 8.PAINTING8.3.1 COLOURHistorically, railings were painted in 'muted' or 'metallic' colours. In the early 18th century dark grey or grey-blue tones were not unusual. At the end of the 18th century, a patinated bronze became fashionable, although dark green, known as 'Brunswick Green' was very widely used. Black has been used on railings in the 18th century and before, but it became more common in the 19th and 20th centuries.Gilding was normally used on railings of mansions and grander town houses or public buildings, to pick out special features such as gate crests, anthems, foliage or other motifs on elaborate compositions. As a matter of general policy, the London Borough of Westminister Council discourages gilding for ordinary railings on historic domestic properties. Where consent is required for gilding, it will normally be refused unless evidence can show that, in a particular case, the proposed gilding is of historical significance and that it would not harm the uniformity or continuity of a group of buildings. 8.3.2 PAINT SYSTEMSTraditional and current conventional paint systems consist of the application of a primer, an undercoat and the finishing coat(s).Paints for all coats within a system will have compatibility with each other and with the metal substrate. There will be adequate adhesion to the substrate and between coats and there should be no under- softening to cause 'lifting', 'wrinkling' or 'bleeding'. For these reasons Kensington Railing Co always obtain all the components of a paint system from the same source, following manufacturers' instructions or specialists' specifications, to ensure such compatibility. 8.3.3 PRIMERSThe type, quality and method of application of the primer are of crucial importance for the appearance and protection of the metalwork. There are different types of primers, which may be more or less suitable for different metals and determine the appropriate type of undercoat and finishing coats. Apart from this type of metal, the choice of the primer depends also on the design and detailing of a specific set of railings and its exposure to weather conditions.Primers will be applied thoroughly, covering all the surface of the metal, including difficult welded corners which are most vulnerable to corrosion. As it is almost impossible to produce a continuous film of adequate and even thickness and free from 'pinholes' with one coat, it is recommended that two coats of conventional primer are applied. Kensington Railing Co apply a second coat of primer, rather than an extra finishing coat, resulting in a longer life for the whole paint system and the metalwork. 8.3.4 UNDERCOATSUndercoats are applied between the primer and the finishing coats. They provide protection to the primer and they form a key-surface of adhesion for the finish. By their relatively thick texture, undercoats increase the thickness of the film; by doing so, they reduce considerably water and oxygen permeability, they smooth the surface of the primed metal to enable the final coat to present an even texture, and they provide adequate opacity for the (often semi-transparent) finish to have an even colour. Very importantly, the relatively thick and flexible layer of the undercoat provides a 'cushion' which absorbs differential micro- movements (due to different consistency and different exposure) between the primed metal and the finishing layers of paint, thus reducing the risk of cracks in the outer film.Undercoat layers are applied evenly and cover the primed metal completely. Two coats are usually preferable to one.8.3.5 FINISHING COATSThese form the external 'skin' of the whole paint system. Their function is to insulate the metal from water and oxygen, to provide a hard protection to the paint system and to give a 'perfect' texture and the desirable colour to the ironwork.There is a very large range of different types of finishing paints in the market. Their differences originate mainly from their chemical constitution. In practice, their performance is assessed on variables such as texture, drying time, surface hardness, elasticity, waterproofing qualities, resistance to weather conditions and atmospheric chemicals, detailed application techniques and even dust repellence, length of potential storage time, and others. The principal criterion in choosing the finishing paint is that it should be compatible with the other paints of the system which is specified for use in a particular case. Kensington Railing Co agree with the London Borough of Westminister Council, 'Preventative maintenance is best achieved by properly planned inspections at regular intervals and by keeping reliable records which should form the basis of a comprehensive maintenance schedule.' Any complete Railing reconditioning should be reviewed yearly, and repainting should take place before the finishing coats cease to provide total protection to the paint system and to the metal. |
