The art of Kalai is the process of coating an alloy surface such as copper or brass by deposition of metal tin on it. The word "Kalai" is derived from Sanskrit Word Kalya Lepa which means "white wash or tin". A cultural Sanksirt work by Keladi Basava called "Sivatattva Ratnakara" mentions "Kalaya-lepa" in the chapter of cookery or "Supashashtra" which means applying Kalai on utensils. People practicing the art of Kalai are called Kalaiwala or Kalaigar. Basically, Kalaigars or Kalaiwalas are community craftsmen.
History
Vessels with Kalai, both on its interior and exterior have been found in the excavations of Bramhapuri at Kolhapur, Maharashtra which adds to the archeological evidence of Kalai Art. From this evidence, P K. Gode, who studied tin coating on metallic vessels in India, stated that the history of tin coating dates back to 1300 C.E. The history of Kalai is also recorded in “Parsibhashanushasana” of Vikaramasimha and also in the famous Ain- I -Akbari by Abul Fazal.
Spiritual approach
The copper vessels with Kalai were used to store water and cook food earlier because of a spiritual belief that copper attracts and transmits a divine consciousness also called “Chaitanya”. The spiritual approach to the use of copper vessels to store water is that Copper and Tin have Sattva-Raja component that is transferred to water.
Scientific approach
Kalai is required to be done on the vessels after approximately every two months of the doing the same. Earlier, copper and brass vessels were used because of their high conductivity. High conductivity of copper vessels reduces the fuel cost. Tin also conducts heat almost as quickly as copper, so there's no question of copper losing its conductivity because of the Kalai. The vessels had to be tin-coated frequently to maintain the taste of the food as after sometime the food tastes bitter and it led to even food poisoning. The copper, in traces gets dissolved in water when the water is stored in a copper vessel for a long period of time. This scientific process is called “Oligodynamic effect”. Copper reacts with certain foods and can lead to gastrointestinal symptoms. By doing Kalai, the deposition of tin layer works as a safe substance between the copper and the food. Tin will melt if the temperature is above 425 degrees Fahrenheit. Tin from the copper vessel wears away with time so usage of metal utensils, so wooden or siliconspatulas should be used. Cooking of acidic foods should be avoided. A chemical reaction between copper and oxygen called Oxidization turn the copper vessels black. If Kalai is not done on the copper vessels, copper will react with the air's moisture and create copper carbonate, which is green in color. This can make a person severely ill.
Process
Kalai can be done in various ways. Virgin grade Tin, caustic soda, sal ammoniac or ammonium chloride, and water are used in the process. The first step of Kalai is to clean the utensil with water. There are two ways of cleaning the utensil further to remove any impurities such as dust. The first is to clean it with caustic soda. The other is to wash it with dilute acid solution which contains gold purifying compound known as ‘Sufa’. If the latter is used, the utensil should be cleaned immediately after applying the dilute acidic solution as it may bear a mark if not done immediately. After the cleaning, the vessel is heated on burning coal for about 2 to 3 minutes. The Kalaiwala, Kalaigar or Kalaikar then digs a small pit in the ground to burn the coal. He/she prepares a temporary blast furnace to do Kalai and blows air through bellows. After the vessel turns pinkish hot, virgin grade tin is applied on the hot vessel. This step is called ‘casting’ by the Kalaigars. The ‘Nausadar’ powder is sprinkled on the vessel. The tin melts rapidly which is then rubbed evenly on the utensil with the help of a cotton cloth or a swab of cotton. The rubbing process is known as ‘Majaay’ in Hindi. A whitish smoke with the peculiarsmell of ammonia is released when the ‘Nausadar’ powder is rubbed on the utensil. A silvery lining appears on the vessel with a shine. The final step of Kalai is to dip the utensil in cold water.
Kalai was earlier done with silver instead of tin but now it would be expensive for the Kalaigars to use silver. As the stainless steel and aluminum ware came into being, the usage of copper and brass utensils reduced which led the Kalaigars to suffer losses. Now-a-days only some hotels and a very few people use vessels with Kalai done on it. As a result, there are a very few Kalaigars left. The art of Kalai is vanishing.
