Paint Removal
We are mostly asked to strip paint from bricks, stone, renders, timber and metal. To see photo examples of these please Click here.
Below is our guide to stripping paint from masonry and some brief technical information.
Painted External Masonry
Masonry is most often painted as protection against our great British weather. Sometimes painting is carried out because its fashionable but all too often it is done to avoid tackling what's perceived as a more difficult or costly job and so hide something. Where this has been done problems can become more serious because you can't see what's going on. This is particularly true of older buildngs with solid walls which rely on the ability of the masonry to efficiently allow the passage of water vapour. This process is often described as allowing the building to breathe. Virtually all masonry construction will absorbe a percentage of the water it receives by way of inclement weather. To what extent depends on several factors including the condition of the mortar joints and the porosity of the building material. In older buildings with solid wall constructions (without a cavity) water and water vapour will permeate through the masonry and as drier conditions prevail externally it will evaporate. In these circumstances it is a matter of balance and the cycle of wetting and drying out is quite normal. Problems only occur when something interferes with or prevents this process. Here we are considering the problem is layers of paint. Relative to the life span of a building paint systems do not last long. Coming under attack from sunlight (UV) temperature changes and air pollutants they soon lose the characteristics such as good adhesion, flexibility and impermeability for which they were originally selected. When this happens a paint systems ability to prevent water absorbtion is much lessened and more importantly any water that does get behind the coating can remain trapped there. One of the first signs that anything is wrong may be dampness on an internal wall. If you have this problem and your home is properly damproofed check there is no water pentration from the likes of leaking downpipes and if not and your external walls are painted then it's worth taking a closer look at this to see if the paint film is sound.
Paint removal?
Removing unsound or unwanted paint without damaging the surface often requires a combination of methods. We always start by using the least aggressive or intrusive method working up the scale as may become necessary. We need to consider many points and although we are talking about stripping paint from masonry the following questions apply equally to any surface brick, stone, wood, or metal where there is a need to ensure the surface is not damaged.
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The Paint System - What type of paint is it? Oil based, water based, natural or synthetic resin based? The list is a long one. All of them can be removed however some are much more difficult than others. Interestingly one of the most difficult to remove is sound limewash which is arguably the least intrusive to masonry as this does allow the transmission of water vapour. We often find limewash under modern masonry paint on older buildings and always test to see if that is the case. Masonry paint should not be used over limewash as adhesion is always poor and it will eventually become detached.
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What material has been over painted? Stone,brick, plaster, timber, metal? Can it withstand any type of paint stripping process? Is the surface likely to be damaged by the use of hand or mechanical tools? steam? pressurised water? paint softening chemicals? abrasives?
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Any practical and logistical problems? These affect the how the paint can be removed including whether the work is internal or external. Is it in an area that can tolerate any proposed stripping process?
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Methods of stripping? After considering the above we can then choose the most appropriate method.
Successfully removing paint particularly from masonry often requires one or a combination of these methods:
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Chemical Stripping Agents - Pastes, poultices and gels applied to the surface of the paint and allowed to react with the paint film usually to soften it and make it easier to remove. In recent years we have thankfully seen an increase in the availability of products that do not include hazardous solvents making them safer to use and more environmentally sound.
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DOFF & Aquilla Steam Systems - These are not the same as the hot water pressure washers you can hire at your local DIY store. They operate at considerably higher temperatures producing steam at high pressure through a lance and should only be available to contractors whose personell have been trained to use them. They can strip certain types of masonry paint without the use of any chemicals.
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Micro Abrasive Systems - We coined this phrase a number of years ago and it's now commonly used to describe air powered systems that fire very fine granules at the surface of the paint to break it down. Most incorporate the use of water to suppress any dust created. All are designed to operate at very low pressures 0.5 - 2.5 bar. The JOS, TORC & FLIROK systems we use are recognised leaders in this field.
Sandblasting Equipment - Most people have heard of this. Regrettably some people still use it to strip paint from or to clean masonry. We have included it here solely to discourage that. It is not the same as any of the micro abrasive systems mentioned above and unless your building is made of engineering bricks sandblasting will almost certainly cause irreversable damage to your brickwork or stone masonry and the mortar joints. We also have blast cleaning equipment but only use it for it's proper intended purpose -The cleaning of Iron & Steel!
Philip Wright - Kimbolton Restoration Ltd. 2007.
