GENERAL NOTES FOR THE SUCCESSFUL APPLICATION OF LIME WASHES

Lime in general is an extremely versatile building medium, used in some form or another on most buildings built before the middle of the 19th Century.

Despite the huge array of paints that have been introduced this century there are still many occasions that limewash is simply the best and cheapest form of decoration for historic buildings, none more so than Churches.

Buildings such as these are often constructed using solid walls with two skins of dressed stone with a rubble core fill between. They are unlikely to contain damp-proof courses and will always contain varying degrees of moisture, depending on the time of year and the overall condition of the building fabric (for instance, how good is the pointing? Is there leaking rainwater?).

Moisture must be allowed to migrate freely through these walls to evaporate and this is best achieved using lime based mortars, renders and paints. Changes in temperature and humdity will often result in condensation and a porous, absorbent finish is desirable to prevent the walls "running" with water.

Research carried out at all levels has proven limewash to be the most permeable type of decoration known, allied to the fact that has been used as a decorative finish for hundreds of years throughout the world. It is without doubt, a tried and tested product!

The material being applied to the wall surface is calcium hydroxide, suspended in water.  The water evaporates and atmospheric carbon dioxide readily combines with the wash to form calcium carbonate, a process known as carbonation.  During the carbonation process the lime wash hardens, develops its colour and makes it bond to the substrate so that a thin sheet of limestone is formed on the surface.

The most important part of the carbonation process is not to allow the limewash to dry too quickly.

Painting of limewashes should be avoided in strong drying winds or under strong direct sunlight. If works do continue under such unfavourable conditions, measure should be taken to protect the works, such as fog misting with a spray.

PREPARATION

Limewash is normally applied to a sympathetically porous substrate, such as lime plaster, clay bricks, soft stones etc.

Surfaces should be clean and free of grease and vegetable matter such as lichens etc. All loose or flaky material should be removed.

Any organic growth should be treated with a suitable biocide in accordance with the manufactuers instructions with all dead material being removed prior to lime washing.

APPLICATION

Limewash is supplied in a plastic container. Upon opening, you will find several inches of clear water lying on top of settled limewash. This water should not be discarded - simply mix in with the settled lime below.

Apply limewash using a large, long hair brush. Application should be vigorous using horizontal, vertical and diagonal strokes, ensuring the wash is applied as thinly and evenly as possible. If applied too thick, crazing and cracking will occur when the limewash hardens off. If this should occur, wash off using hot water and a stiff bristle brush and ensure that the new coats are properly applied.

Regulate work to one coat a day, allowing individual coats time to carbonate as re-coating too soon may result in the previous coat pulling away and hampering proper carbonation.

It is important to regularly stir the limewash during the painting process.  The best tool for this is a balloon whisk, but a simple stick will be effective.  Stir vigorously until the contents are one and continue to do so every ten to fifteen minutes during application. The last limewash from the tub should be as thin as the first.

HEALTH & SAFETY COSHH ASSESSMENT

Limewash is alkaline, so every effort must be made to prevent any from getting into your eyes. If this happens, rinse the eye thoroughly for several minutes.  If discomfort should continue, seek medical attention as soon as possible.  It is advisable to keep an eye bath and suitable fluid to hand, for irrigation purposes.

The wearing of gloves is advised as limewash can dry the skin and will possibly have more serious affects for sufferers of Dermatitis.

There are no risks from fumes, vapours or burning when heated.  By virtue of the way it should be applied, lime washing can be a messy operation and the wearing of overalls and suitable protective equipment is advised.

Splashes of limewash should be cleaned up promptly.

For further information, please don't hesitate to contact us.