There are as many recipes as there are makers of it. We include several recipes here.
Whitewash, or calcimine, kalsomine, or calsomine is a very low cost type of paint made from slaked lime (calcium hydroxide) and chalk (whiting). Various other additives have also been used.
A typical recipe is:
a) 62 lb quicklime, shake with 15 gallons water in a covered barrel. Wait until steam stops. Stir occasionally.
b) 2.5 lb rye flour, beat up with 1/2 gallon cold water the 2 gallons boiling water.
c) 2.5 lb salt. dissolve in 2.5 gallons water.
Mix (b) and (c) then pour into (a) and stir until all is well mixed.
Consistency is perfect for brushing.
Lime is a natural and sustainable product, and has traditionally been used throughout the world to protect and decorate buildings. In North America, modern paints and coatings replaced the use of lime early in the 20th century.
Recently, people have begun to rediscover the many benefits of this amazing natural product. Lime coatings have proven invaluable in the restoration of old buildings, the perfect complement to rammed earth and straw bale construction, and as a replacement for modern coatings such as cement stucco and paint.
Lime in its raw state is calcium oxide CaO made by heating calcium carbonate CaCO3 over 9000C to release carbon dioxide (40% by weight). After slaking with water to Ca(OH)2, it can be used in its natural white state or tinted using lime-tolerant pigments to create beautiful, lasting color. When used in a plaster, paint or wash, slaked lime absorbs carbon dioxide from the air as it cures, reverting back to its natural state to form a tough, permeable coating of limestone.
Lime coatings have distinct advantages over more modern products:
- Waterproof when cured
- Vapor permeable, allowing moisture to escape
- Completely UV resistant
- Will not shrink or crack
- Stain resistant
- Unaffected by temperature fluctuations when cured
- Easy and inexpensive to make.
Here are some general guidelines for the use of lime coatings:
- Application of lime renders and coatings must take place within a set temperature and humidity range for proper carbonation
- Lime is applied in the proper thickness to allow for carbonation and adherence
- Lime, as calcium oxide, is caustic and requires simple protection and safety measures during application
- Substrate must be evaluated for compatibility with lime coatings and properly prepared or primed
For thousands of years lime has proven itself to be a stable and long lasting building material. Realize the same benefits in your modern world with the use of lime plasters, washes and paints
Limewash and whitewash are made stronger with CO2, animal blood (usually of pigs), adobe as substrate; pozzolanic materials and also cement make it harder-wearing; linseed oil and also wheat flour improve adhesion to substrate; dilute glues improve paint toughness.
Whitewash cures through a reaction with carbon dioxide in the atmosphere to form calcium carbonate in the form of calcite, a reaction known as carbonation.
When the paint initially dries it is uncured, and has almost no strength. It takes a period of anything up to a few days, depending on climate, to harden.
It is usually applied to exteriors. Occasionally it is colored and used on interiors, such as the hallways of apartment buildings, but it is not popular for this as it can rub off onto clothing to a small degree.
Whitewash is especially effective on adobe-like materials because it is absorbed easily and the resultant chemical reaction hardens the substrate. Also whitewash and adobe are both very low cost building materials.
The coating has anti-microbial properties that provide hygienic and sanitary benefits for animal barns.
Lime has a long history of use, serving both functional and decorative purposes. A limewash is a thin coating that serves as a protective layer but also lends itself wonderfully to artistic expression. When applied, the lime within the wash begins to react with carbon dioxide in the atmosphere in a process called carbonation, gradually returning it to its original state, limestone. As it reverts, the crystals within the lime expand and adhere to the surface below.
Lime and ochre provide a synergy with the additional light refraction from the lime crystals combined with the texture of the ocher. This colored plaster then provides a finish coat eliminating the need for painting. Ochers and earths produce warm shades and are permanent to UV. Oxides produce cool shades and are often used in small quantities with ochers.
To obtain colored lime plaster:
- ochers and pigments can be added in ratio to the weight of lime to be employed, before the addition of any aggregate. This ratio should not exceed 20%. If using lime putty rather than hydrated lime powder, half the weight of the putty should be calculated.
- To mix, slake the pigment in an equal volume of water to create a homogenous paste. This can then be added to the wet plaster mix.
- The use of a mixing paddle attachment is recommended. When adding pigment color to plaster, it should be considered as an aggregate. Therefore it may be necessary to adjust the water to your mix, particularly when using Ochers.
- Rather than adding additional water, it may be sufficient just to thoroughly saturate the substrate before application of the plaster, and if necessary, light misting of the plaster with water while it is being worked.
Proper Atmospheric Conditions
Proper temperature and humidity are required for the carbonation process to be successful:
- Temperature should not be below 41 ºF (46 ºF for dark colors) at any time during the application or carbonation process. Do not allow freezing to occur.
- In temperatures above 86 ºF or in very low humidity, surface and subsequent coatings must be misted with water.
- Exterior coatings should be protected from wind and sun to protect from drying too quickly an opaque covering such as damp canvas or burlap works particularly well.
- Surfaces must not have a surface temperature below 41 ºF (46 ºF for dark colors) and must not be excessively hot or excessively wet.
- The most critical period of carbonation is the first two to three days.
Lime wash is pure slaked lime in water. It produces a unique surface glow due to the refraction of calcite crystals. Limewash and whitewash both cure to become the same material.
When limewash is initially applied it has very low opacity, which can lead novices to overthicken the paint. Drying increases opacity, and subseqent curing increases opacity again.
Additives that have been used include water glass (silica gel), glue, egg white, Portland cement, salt, soap, milk, flour, earth, blood.
Whitewash is sometimes coloured with earths to achieve colours spanning the range of broken white, cream, yellow and a range of browns.
Historically pig's blood was added to give the colour Suffolk pink, a colour still widely used on house exteriors in some areas of the UK. Animal blood also further reinforces the earth based substrate to some degree.
Pozzolanic materials are occasionally added to give a much harder wearing paint finish. However paint with these added has a short open time, so pozzolan can only be added at point of use.
Linseed oil is sometimes added (typically 0.5-2%) to improve adhesion on difficult surfaces.
Cement addition makes a harder wearing paint in white or grey. Open time is short, so this is added at point of use.
Dilute glues improve paint toughness.
Wheat flour has been used as a strength-enhancing binder. Salt is usually added to prevent the flour going mouldy later in damp conditions. The use of salt brings its own issues.
Simple lime paints are very low cost. A 25kg bag of lime makes around 100kg of paint, and costs around £6 in the UK (2008).
The complete success is well known of the formula for whitewash adopted by the United States Government as a coating for lighthouses, and for its effectual prevention of any moisture striking through the walls. It is simply the mixing with fresh water, in the most thorough manner, of three parts Rosendale cement and one part of fine clean sand, thus giving a gray or granite color, dark or light according to the color of the cement; if a very light color is desired, lime is used with the cement and sand; if brick color is sought,, enough Venetian red is added to the original mixture to insure that result.
Care is exercised to have the various ingredients well mixed together in applying the wash, have the wall wet with clean, fresh water, followed immediately with the cement wash. This method preventing the bricks from absorbing the water from the wash too rapidly, and it also gives time for the cement to be properly set.
The mixture is made as thick as can conveniently be applied with a whitewash brush in the usual manner, and the wash is well stirred during the process of its application. It is stated, however, that though this mixture is so admirably suited for the purpose in question, it cannot be used to advantage over paint or whitewash because it needs to bond with the concrete or brickwork underneath.
For the purposes of this article, lime powder refers to Hydrated Lime Type S. This is lime that has been industrially slaked and is ready for immediate use. All ratios in this instruction have been carefully calculated by weight using this lime powder to ensure proper proportions.
Not all lime is created equal. Be sure to purchase from a quality building supply store. The lime should not be more than 2 years of age and should be a striking white. Do not accept lime that is gray in color.
Lime washes have traditionally been made using lime putty, lime that has been slaked or soaked and comes in a paste form suspended under water to prevent carbonation.
Before use in washes it must be sufficiently thinned to a suitable fluidity. Thus the water content when using lime putty can vary considerably. When following this article's weight ratio guidelines for pigments and additives, it is up to the end user to make the proper conversions to determine ratios when tinting washes made from putty.
Choosing a Suitable Surface
For lime to properly adhere to a surface the two must be:
- Chemically compatible: such that lime will not adversely react with the surface, causing the two to separate, (the lime flakes or falls off). As with lime plasters, the supporting surface must be able to withstand a pH of 12 or more. Otherwise use a primer.
- Mechanically compatible: such that there is sufficient porosity and texture, referred to as "key", to allow the lime crystals to expand, "lock" onto and penetrate the surface.
A limewash has more rigid requirements for compatability with the substrate than whitewash because it is a thin coating.
Surfaces suitable for limewash without a primer are:
Surfaces that are unsuitable for limewash:
- Lime plaster and renders
- Lime and cement based mortars and renders that have proper tooth and porosity
- Previously lime washed supports
- Masonry supports such as brick, stone, terra cotta (mud) and cement block
- Asbestos cement
- Dry wall
- Plaster block
- Hard troweled renders and plasters
- Plaster coating
- Painted interior surfaces
- Smooth surfaces
- Nonporous surfaces.
Preparing Suitable Surfaces
Preparing Suitable Surfaces (Lime and Masonry)
The surface must be fully cured. Very smooth surfaces that don't have enough tooth (roughness) for the lime to bond with may require texturing with medium abrasives or a wire brush. Dust and loose debris should be removed by brushing or dusting, and then washing.
Next, the surface must be prewet (humidified) before each layer of wash is applied. Prewetting can easily be accomplished with a fine mist of water using such tools as a plastic spray bottle, pump sprayer or a garden hose with a suitable mist nozzle.
Prewetting the surface prevents it from absorbing water from the limewash itself, which could impair the critical carbonation process. A light dampness is desired, but too much water on the surface will interfere with cling and coverage.
Depending on the surface, humidity and temperature, it may be necessary to wait several hours (up to over-night) after you prewet before you begin the limewash application.
Dealing with Unsuitable Surfaces
Each surface must be assessed for both chemical and mechanical suitability, and must be fully cured. The unnatural denseness of some modern coatings such as plasters, paints and cements can prove particularly difficult for traditional limewashes to adhere to because they can have both chemical and mechanical incompatibilities. Readymade primers specifically made for use with traditional limewash contain modern additives that alleviate some of these obstacles.
The limewash effect (visual appearance) is determined by the water to lime volume ratio, and can be divided into four distinct types. Each type corresponds to a unique recipe:
- Liming Coat: a thicker application with a more opaque look
- Wash: partially transparent, but with a strong coloring
- Tempera: medium-transparent, with the surface effect of tempera paint
- Patina: strongly transparent with an aged look.
Water to Lime Ratios by Volume
Coloring Limewashes with Pigments
For limewash, pigments are added after the water and lime are thoroughly mixed. Slake (wet) the pigment in an equal amount of water to form a paste. This paste can be left to soak overnight if desired. Add the pigment paste to the limewash and stir – an electric paint paddle is recommended for complete dispersion. How much pigment you add depends upon individual pigment density, intensity of color desired, and chosen recipe.
Here when referring to a maximum percentage of pigment, we mean the saturation limit. Beyond this percentage, the pigment no longer adds intensity of color but instead begins to thicken the mixture, increasing the load that is to be fixed by the lime. Therefore, too high a percentage of pigment will result in mechanical failure of the limewash. The chart below lists limits for Earths, Ochers and Oxides. Note that as the volume of water in your limewash increases so can the weight of pigment before saturation occurs. Use this as a guide – these are upper limits; you can use less than indicated.
Maximum percentage in relation to lime powder by weight
(For Natural Yellow, Natural black and Natural red use instead the maximum percentages shown for Oxides.)
Additive Binders for Enhanced Adherence
Additives have traditionally been used with limewash to enhance its adhesion to the support surface. They generally fall within three categories:
- Resins such as linseed oil
- Glues such as casein or methyl cellulose
- Modern binders like PVA, (polyvinyl acetate)
Linseed Oil is inexpensive and natural but it will alter the matt (flat) quality of a limewash, (it will also yellow over time).
Casein is inexpensive, natural and will not alter the matt quality of the coating. Prepare by soaking in hot water at a ratio of 2.5 pounds casein per gallon of water. Allow mixture to stand overnight.
Methyl Cellulose is a plant-based glue. It is inexpensive, and has the additional benefit of enhancing water retention. This slowing of the drying process is especially important in dry, hot or windy conditions where drying too quickly in the first two or three days can interfere with the important carbonation process. Do not use in wet conditions or on overly wet supports. Preparation: 20 grams per gallon of water. Allow mixture to stand overnight. It is the weakest of the binder additives, and really serves more to extend the "open time" of the limewash so that it does not dry too quickly in dry or hot conditions.
PVA, (polyvinyl acetate) is strong and inexpensive. We recommend our Acrylic Resin - a superior product that, unlike other PVA products, dries crystal clear. Dilute the proper amount with some of the water used from the chosen recipe then add to the remaining limewash mixture.
Additives are added after the initial mixing of the lime and water at a ratio of 1 to 10% of the volume of prepared limewash, before adding pigment. These additives can enhance binding strength and thus help to overcome less than perfect surface and application conditions. They can also assist in stabilizing the pigments within the limewash mixture. Since these are positive effects, their use is fairly common. However, these additives will also affect the porosity of the final lime coating, and a decision on whether to use them or not should take this fact into account.
One important rule: always add the same ratio of additive binder for each successive coat. Also, never exceed this 10% volume ratio as your limewash will no longer be a lime coating, but will primarily become a distemper paint.
It is best to test your mixture to be sure ratios are correct and that, when dry, the desired color and effect has been achieved. Dry color will be lighter than when wet. Limewashes also will dry to be more opaque than when wet, so do not make the mistake of applying too much in one coating.
Several thin coats are the key to limewash success – never apply too thick. For exteriors, 5 coats is recommended. For interiors, 3 coats should suffice. Lime is hard on brushes so choose a longhair masonry brush, (or sponges for patina applications). For mixing, the use of an electric paint-mixing paddle is recommended, along with rubber buckets, rubber gloves and eye protection. Mix only the amount of limewash to be used in one day.
Secco or "dry application" for cured surfaces: prewet the porous surface and allow it to sit several hours or overnight. When applying, do not spread the wash out as you might do with paint – apply with an even stroke and pressure to work the wash into the surface. Stir the wash between strokes.
Water can be added to dilute the thick layer of wash that will be found at the bottom of the bucket as the wash is used. Apply your strokes vertically, then horizontally, finishing with a vertical stroke. When applying successive layers, allow the limewash to dry for 1 to 3 days between coats. Mist the surface with water and use slightly higher ratios of water with each successive coat – this ensures good adhesion and carbonation.
Fresco or "wet application" for partially cured, damp lime plasters and renders: in the Fresco technique, limewash is painted onto fresh, wet plaster using similar application techniques as with Secco. However for Fresco, use the lime powder-to-water dilution for Tempera – 1 part lime to 4 to 6 parts water. This technique requires that the surface must have carbonated (hardened) enough so as not to deteriorate as it is being brushed, but not be excessively dry as to inhibit proper adhesion of pigments with the lime in the surface. Technique and climatic conditions play a major factor in application time and success.
A thicker limewash is often used as a maintenance coat on interior or exterior masonry. Since it is thicker and more opaque than a wash, brush strokes will be apparent. Be cautious about using this recipe – although at first it may seem to cover better and be successful without all the work of several thinner coats, liming coats can easily be applied too thick which will result in failure due to poor application technique:
- 1 part water
- 1 part lime powder
- Additive binder at a ratio to the total volume of limewash mixture at no more than 10%
- Pigment by weight (ratio to lime powder) of no more than 10% Ochers, 5% Oxides maximum
A wash has less texture than a liming coat, but still masks the surface. To obtain the best result, stir between every stroke.
- 2 part water
- 1 parts lime powder
- Additive binder at a ratio to the total volume of limewash mixture of 1-10%
- Pigment by weight (ratio to lime powder) of no more than 22% Ochers, 15% Oxides maximum
Lime Tempera is like a watercolor in its color intensity, utilizing both round and flat brushes. It is applied in both dry and fresco techniques:
- 4-6 part water
- 1 parts lime powder
- Additive binder at a ratio to the total volume of limewash mixture of 1-10%
- Pigment by weight (ratio to lime powder) of no more than 65% Ochers, 35% Oxides maximum
Patina coats give great transparency that will enhance the texture of a surface using either brush or a sponge. Used with both the dry and fresco techniques, it also acts to even out areas:
- 20 part water
- 1 parts lime powder
- Additive binder at a ratio to the total volume of limewash mixture of 1-10%
- Pigment by weight (ratio to lime powder) of no more than 95% Ochers, maximum of 55% oxides.
Lime Plasters and Renders
Historic Whitewash Formula
Mix Parts "A" & "B" for a brushable consistency.
- Part A:
- Salt: Common Sodium Chloride: 12 pounds salt
- Alum: Powdered, Common Potash Aluminum: 6 ounces alum
- Molasses: Unsulfured, Light Brown/Clear: 1 quart molasses dissolved in 1.5 gallons water
- Water: Potable: 1.5 gallons water
- Part B:
- Quicklime: Quick Lime if you want to "slack" it, or Non Caustic, Hydrated Lime if you don't want to "slack" it. 50 pounds (1 sack) quick lime, mix with 5 gallons hot water. Allow to stand for 24 hours.
- Optional: Type I or Type II Portland Cement: White, non-staining, Type I or Type II Portland Cement can be substituted for up to ten percent of the lime material to produce a more durable coating.
Notes: Use this formula at your own risk. Ordinary lime, or quick lime, is caustic. To get the lime you want for whitewash you have to "slack" the quick lime with hot water at least overnight. The result of slacking is hydrated lime, or Ca(OH)2. But if the slacking is not complete or thorough it can burn your skin. If you are worried about incomplete slacking, buy hydrated lime instead of quick lime. Regular garden lime, which is really ground limestone, is of no use.
There is a traditional whitewash made as follows:
Mix the flour and salt, then pour into the quicklime. Stir till well mixed. Consistency is perfect for brushing.
- 62 lb quicklime, shake with 15 gallons water in a covered barrel. Wait until steam stops. Stir occasionally.
- 2.5 lb rye flour, beat up with 1/2 gallon cold water the 2 gallons boiling water.
- 2.5 lb salt. dissolve in 2.5 gallons water.
Quick Lime can be used. When lime is added to moisture it heats up. Really heats up. Do not use plastic buckets or utensils. They will melt.
Whitewash is really only lime and water. Other ingredients added for durability. We use one cup salt (table salt - sodium chloride), 2 cups lime, 2 cups calcium chloride to a gallon of water. The consistency should be like milk. For larger amounts - a stiff paste can be made of 38 lbs quicklime to 8 gallons of water or 50 lbs hydrated lime to 6 gallons of water, then thinned with additional water to the milk consistency.
Other names of the limes used are chemical hydrate, ag spray hydrate, finishing lime, pressure hydrated lime. The more refined the lime the smoother the paint, especially important if you plan to spray the paint.
One old timer uses kerosene in the mixture. She likes the oil base for painting.
Caution: Prepare whitewash in well ventilated areas. We always do this outside.
Hydrated Lime or option is casein, which makes the solution oil-based also. In the days when they had an abundance of milk, it was used as the liquid - this gives the whitewash a latex-like quality. Anyway the calcium chloride added keeps the paint from being so chalky and adds to the durability, nice if used where temperature get very cold. White glue or white Portland cement can also be added to get a heavy cream consistency if you want a thicker paint.