Cleaning Historic Buildings in the UKOver centuries historic and ancient buildings acquire surface pollutants and layers of paint that spoil the look and structure of the original substrate. We can remove these residues using non-abrasive, environmentally sound methods. |
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Historic Building Cleaning UK
Before stripping any historic surface, ask yourself if it is really necessary, Stripping may well remove interesting earlier surfaces, and the wrong method can damage the ancient fabric underneath. In some cases it may be unjustified on historical or aesthetic grounds, particularly if the intention is to leave items stripped that were always meant to be covered.
In many old buildings there may be paintings on plaster, stone and timber (such as panels, doors and beams) that are hidden beneath layers or subsequent paintwork. There could also be ancient paint types of technical interest or valuable colour schemes which have remained undisturbed for many years and which contribute to the archaeological interest of the building. Where there is a likelihood that such paintwork exists, records should be kept and both investigation and treatment should be done by a specialist conservator.
• Softwoods in Victorian and Edwardian era buildings were often intended to be painted. Internal doors and areas of panelling have sometimes been severely damaged as a result of the vogue for stripping back to the natural finish only to deliver an inappropriate final finish.l
• Prolonged soaking of items, such as doors, in caustic baths can cause lasting damage to the timber.
Top
Methods of removal from Historic Buildings
All forms of paint or grime removal are laborious and slow. Different paints or polutants respond to different methods and it is therefore helpful to be able to identify the thickness and the type of paint (i.e. water or solvent thinned, bitumen or polyurethane based, etc.) that has been applied, also the nature of the substrate, before deciding upon its means of removal. Manufacturers of the paint can often provide useful and critical advice. It may be necessary to try several techniques, or a combination of methods to achieve success. Tests should be made over small trial areas in the first instance to see if the paint can be lifted and to ensure that the substrate will not be damaged.
Heritage Victoria or any of the equivalent state government heritage agencies throughout Australia can be contacted for guidance.
Water washing can be helpful in removing limewashes, whiting and soft (size-bound) distemper.
When removing paint from plaster KEEP WATER TO THE MINIMUM; prolonged soaking will soften plaster, especially gypsum-based historic plasters.
Steam stripping is usually undertaking using an appliance designed mainly for stripping wallpaper. It generates steam at low pressure and the steam is applied to the paint film via a hose capped with a perforated metal applicator.
Water-thinned paints are softened by steam and then removed with a sponge, brush, scraper and water. Steam in conjunction with a solvent stripper can be effective in removing multiple applications of old emulsion paint, including polyvinyl emulsion.
There are two main types of chemical paint removers: solvent (non caustic) and alkaline (caustic). Both are available in liquid, gel and poultice form. Manufacturers provide instructions on application, removal and methods of disposal.
All chemical paint removers constitute a health risk. Some can burn on contact with the skin and vapours and sprays are toxic if inhaled. Operators should work in well ventilated areas, wear protective clothing and face masks. The strippers are also flammable.
Solvent (non caustic) removers are usually based on methylene chloride. They are effective in removing oil-based paints, tar and some emulsions.
They are available as either water-rinsable which enables the wax residues to be removed by a thorough wash down or sprit rinsable when wax deposits can be removed with white spirit.
Alkaline (caustic) removers are based on caustic soda, potash, washing soda or similar material. They should only be used as a last resort. They are easily absorbed by porous surfaces and the harmful residues are very difficult to remove. Application should be restricted to small areas. They are NOT SUITABLE for plywood, veneers or hardboard and can be harmful to brickwork, stonework, metal and most types of plaster or putty. They may raise the grain of timber and they may also darken or bleach some woods.
Poulticing may be necessary for stubborn areas of ancient paintwork where paint is embedded in pits and grooves such as brickwork, stone ashlar and timber beams. The poultice may be made up by using powdered clay, such as attapulgite or sepiolite which is added to water and mixed to a paste together with a solvent stripper. The mix once applied is covered with a thin plastic film that helps to impede evaporation of moisture in the paste. The paste is removed with a knife and the surface is washed down thoroughly with clear water; a sponge or bristle scrubbing brush may be necessary to remove any paint residues. Proprietary caustic based poultices are also available.
Manual abrasive methods such as scraping or carborundum block and water (laborious but often effective) should be used in preference to powered tools.
Powered tools such as sanders, are generally only suitable for flat surfaces. Scratches on the surface is a common result.
Blast cleaning should only be undertaken by an experienced contractor and not used on stone and brick surfaces which can be irreparably damaged by blast cleaning.
Whilst blasting is useful on cast iron but it will destroy a smooth surface on wrought iron. Priming of cast iron immediately after blasting is necessary to avoid surface rusting.
Hot air strippers are not suitable for removing water-based paints in historic buildings, some primers and undercoats, or for removing paint from metal or plaster. They should only be used on masonry when thick layers are to be removed when used on window frames the glass should be protected against cracking by heat which the absence of flame decreases the risk of fire damage to the surface of wood can become slightly scorched and this system has been known to ignite flammable materials such as dust in sash boxes.
Blow-lamps or blow-torches are often quicker but pose a fire hazard. The paint itself may catch fire rotted timber below the paint film ignite and smoulder without being immediately noticeable and electrical insulation may also be unwittingly damaged. Dust in the sash boxes become ignited and it is easy to scorch wood and crack glass.
Top
Specific problems
Most methods of removing paint from brick or stone will damage the base material to some extent and it may be nigh on impossible to remove from porous brick or stone. IMAGE 3 (b/w print 150 mm x 100 mm)
Carefully removing the overpainting has revealed these honour boards and painted banners which have then been conserved by professional painting conservators.
There is no general solution to the removal of graffiti but it is important to begin treatment as soon as possible so that the paint does not have time to harden. Long standing aerosol paints are almost impossible to remove from porous surfaces such as brickwork and stonework. There is also a risk of spreading the paint and increasing absorption in the process. Cleaning with an air abrasive pencil using a suitable fine abrasive, followed by toning down the cleaned patch by rubbing with stone or brick dust, may be successful.
A solvent based (non-caustic) poultice should be tried; if this fails an alkaline (caustic) remover in poultice form might be effective. The brick and stone must be thoroughly washed afterwards. A second poultice (without the chemical incorporated) can be applied to help draw out the residual salts.
Anti-graffiti coats are available to protect walls but they can create problems by trapping moisture and salts behind an impermeable membrane.
Before stripping any historic surface, ask yourself if it is really necessary, Stripping may well remove interesting earlier surfaces, and the wrong method can damage the ancient fabric underneath. In some cases it may be unjustified on historical or aesthetic grounds, particularly if the intention is to leave items stripped that were always meant to be covered.
In many old buildings there may be paintings on plaster, stone and timber (such as panels, doors and beams) that are hidden beneath layers or subsequent paintwork. There could also be ancient paint types of technical interest or valuable colour schemes which have remained undisturbed for many years and which contribute to the archaeological interest of the building. Where there is a likelihood that such paintwork exists, records should be kept and both investigation and treatment should be done by a specialist conservator.
• Softwoods in Victorian and Edwardian era buildings were often intended to be painted. Internal doors and areas of panelling have sometimes been severely damaged as a result of the vogue for stripping back to the natural finish only to deliver an inappropriate final finish.l
• Prolonged soaking of items, such as doors, in caustic baths can cause lasting damage to the timber.
Top
Methods of removal from Historic Buildings
All forms of paint or grime removal are laborious and slow. Different paints or polutants respond to different methods and it is therefore helpful to be able to identify the thickness and the type of paint (i.e. water or solvent thinned, bitumen or polyurethane based, etc.) that has been applied, also the nature of the substrate, before deciding upon its means of removal. Manufacturers of the paint can often provide useful and critical advice. It may be necessary to try several techniques, or a combination of methods to achieve success. Tests should be made over small trial areas in the first instance to see if the paint can be lifted and to ensure that the substrate will not be damaged.
Heritage Victoria or any of the equivalent state government heritage agencies throughout Australia can be contacted for guidance.
Water washing can be helpful in removing limewashes, whiting and soft (size-bound) distemper.
When removing paint from plaster KEEP WATER TO THE MINIMUM; prolonged soaking will soften plaster, especially gypsum-based historic plasters.
Steam stripping is usually undertaking using an appliance designed mainly for stripping wallpaper. It generates steam at low pressure and the steam is applied to the paint film via a hose capped with a perforated metal applicator.
Water-thinned paints are softened by steam and then removed with a sponge, brush, scraper and water. Steam in conjunction with a solvent stripper can be effective in removing multiple applications of old emulsion paint, including polyvinyl emulsion.
There are two main types of chemical paint removers: solvent (non caustic) and alkaline (caustic). Both are available in liquid, gel and poultice form. Manufacturers provide instructions on application, removal and methods of disposal.
All chemical paint removers constitute a health risk. Some can burn on contact with the skin and vapours and sprays are toxic if inhaled. Operators should work in well ventilated areas, wear protective clothing and face masks. The strippers are also flammable.
Solvent (non caustic) removers are usually based on methylene chloride. They are effective in removing oil-based paints, tar and some emulsions.
They are available as either water-rinsable which enables the wax residues to be removed by a thorough wash down or sprit rinsable when wax deposits can be removed with white spirit.
Alkaline (caustic) removers are based on caustic soda, potash, washing soda or similar material. They should only be used as a last resort. They are easily absorbed by porous surfaces and the harmful residues are very difficult to remove. Application should be restricted to small areas. They are NOT SUITABLE for plywood, veneers or hardboard and can be harmful to brickwork, stonework, metal and most types of plaster or putty. They may raise the grain of timber and they may also darken or bleach some woods.
Poulticing may be necessary for stubborn areas of ancient paintwork where paint is embedded in pits and grooves such as brickwork, stone ashlar and timber beams. The poultice may be made up by using powdered clay, such as attapulgite or sepiolite which is added to water and mixed to a paste together with a solvent stripper. The mix once applied is covered with a thin plastic film that helps to impede evaporation of moisture in the paste. The paste is removed with a knife and the surface is washed down thoroughly with clear water; a sponge or bristle scrubbing brush may be necessary to remove any paint residues. Proprietary caustic based poultices are also available.
Manual abrasive methods such as scraping or carborundum block and water (laborious but often effective) should be used in preference to powered tools.
Powered tools such as sanders, are generally only suitable for flat surfaces. Scratches on the surface is a common result.
Blast cleaning should only be undertaken by an experienced contractor and not used on stone and brick surfaces which can be irreparably damaged by blast cleaning.
Whilst blasting is useful on cast iron but it will destroy a smooth surface on wrought iron. Priming of cast iron immediately after blasting is necessary to avoid surface rusting.
Hot air strippers are not suitable for removing water-based paints in historic buildings, some primers and undercoats, or for removing paint from metal or plaster. They should only be used on masonry when thick layers are to be removed when used on window frames the glass should be protected against cracking by heat which the absence of flame decreases the risk of fire damage to the surface of wood can become slightly scorched and this system has been known to ignite flammable materials such as dust in sash boxes.
Blow-lamps or blow-torches are often quicker but pose a fire hazard. The paint itself may catch fire rotted timber below the paint film ignite and smoulder without being immediately noticeable and electrical insulation may also be unwittingly damaged. Dust in the sash boxes become ignited and it is easy to scorch wood and crack glass.
Top
Specific problems
Most methods of removing paint from brick or stone will damage the base material to some extent and it may be nigh on impossible to remove from porous brick or stone. IMAGE 3 (b/w print 150 mm x 100 mm)
Carefully removing the overpainting has revealed these honour boards and painted banners which have then been conserved by professional painting conservators.
There is no general solution to the removal of graffiti but it is important to begin treatment as soon as possible so that the paint does not have time to harden. Long standing aerosol paints are almost impossible to remove from porous surfaces such as brickwork and stonework. There is also a risk of spreading the paint and increasing absorption in the process. Cleaning with an air abrasive pencil using a suitable fine abrasive, followed by toning down the cleaned patch by rubbing with stone or brick dust, may be successful.
A solvent based (non-caustic) poultice should be tried; if this fails an alkaline (caustic) remover in poultice form might be effective. The brick and stone must be thoroughly washed afterwards. A second poultice (without the chemical incorporated) can be applied to help draw out the residual salts.
Anti-graffiti coats are available to protect walls but they can create problems by trapping moisture and salts behind an impermeable membrane.
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