Aranmula Kannadi and Its secret metal combination
Producing distortion free images the art of making metal mirrors has long been practiced in various parts of the Old World. By 1400 BC, bronze containing as much as 30 weight percent in tin were used to create mirrors. Although brittle, high – tin bronzes also known as speculum metal, yielded a highly polished surface & a clear reflected image.
The art of making metal mirrors by casting & polished copper-tin bronze was well understood in India & these mirrors were very popular for their clarity, Indeed, the ancient art of making metal mirrors is still practiced without modification, by a few family-based artisans in Aranmula, a small village in southern India. As traditional as the mirror making technology is the artisan’s belief that the composition of the metal-mirror is divine & that some undisclosed metal alloy with the copper & tin are responsible for the distortion free images.
How the secret metal combination found?
A few centuries back the high priest of Aranmula Parthasaradhy temple found that the crown made for deity was cracked. The local king then summoned the head of the bronze smith clan and ordered him to make a new crown within three days.
The crown made out of the compilation of copper and tin turned out to be a marvel of art and craft. It was silver like color, brittle like glass, shone with rare brilliance, and when cleaned acquired the quality of reflection. The makudam or crown as kannadi bhimbom(mirror image) was preserved in the Aranmula temple till 1946. The casters soon worked out the ratios different metals used.
The chieftain of aranmula liberally patronized that craft persons and even laid down an order that the mirror should form one of the eight auspicious articles used in all Hindu religion rites including marriages.
They then made a small KUMKUMA CHEPPU or vermilion container, in bronze and fitted
it with a small bronze and fitted it with a small bronze mirror on the cover, this become very popular among the elite of malayali society. Under the patronage of a few aristocratic ladies the vaalkannadi (Hand held mirror) flourished.
There has been the mentioning of metal mirror in many puranas including Rig-Veda. Even in the carvings of Kajuraho there has been depiction of hand held mirrors. The mirror is oval shape or as per the ancient, it is shaped as the ‘YONNI MUKH’ or Vaginal face. It depicts femininity, just as Shiva Linga depicts masculinity. There are many temples in which the vaalkannadi is used to symbolize Goddess, i.e. Goddess with out form it is a temple dedicated to Goddess Saraswathi, Veena is place next to the mirror. The mirror has a lot of ritualistic importance.
The Vaalkannadi has been used by the ladies of wealthy families for make up and also to admire themselves. It has also been an item of social symbol.
How the Aranmula Kannadi is making?
A kowa or crucible made of wrought iron having an approximate capacity of holding 9 Kg of molten metal is cleaned. The pieces of pure chembu (copper), eeyam (tin) and nagam (zinc) are added in proportion. The mouth of the kowa is sealed with clay. An opening lid made of clay, is also provided. Two vertically opposite holes are provided to pour out the molten metal. One of these holes acts as an air vent.
The Kowa us then placed in an open pit furnace charged with burning charcoal. It is then covered with pieces of thondu, as thondu retains the heat. It is heated to about 400 degree Celsius (approximate melting point of brass).
The molten metal is poured onto flat surface (usually the ground itself). Once cooled, the alloy is then broken into 
pieces using a chuttika(hammer). The broken pieces are then inspected for the quality of the alloy. If found satisfactory, then it is remelted. Else more amount of the alloying elements are added. The molten metal is then poured into the preheated mound. It is then left for cooling. Once cooled, the clay mould is broken and the casting is removed. The casting is checked for any deformities. Usually the master craftsman prepares four to five mirrors and polishes them at a stretch. When one gets heated he does the polishing for the next one while the other cools.
To achieve high quality reflective surface the polishing can go on from one to two days. Once the required polished surface is achieved it is then further polished using a piece of cotton cloth. Then final polishing is done using a velvet cloth. The velvet tends to absorb the oil that was applied earlier on to the mirror. Hence, further polishing is continued on another dry piece of velvet.
The velvet cloth is placed on the ground and the mirror along with wooden blank is moved in the desired direction. Once satisfactory finish is achieved the disk is just heated to separate it from the wooden blank and the mirror is mounted on a brass fame.
The finished mirror would be brighter and beautiful. The making process of aranmula kannadi contains a lots of efforts, expertise and patience.
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And Here it explains….
Aranmula Kannadi is made up of Cu-30% bronze. When bronze containing 30% Sn is slowly cooled, precipitation of brittle Cu3,Sng phase occurring along with alpha solid solution phase gives distortion free image in Aranmula metal mirror. Micro hardness value measured on the mirror under a load of 0.4903N falls between 520-540 VPN which is near to that of hardened steel which explains the brittleness of the mirror and the care needs to be exercised during polishing especially of very large size. Macrostructure shows both columnar and equiaxed grains revealing the direction of solidification as well as the very slow cooling rate to which the mirror disk is subjected to. Microstructure reveals Cu-Sn solid solution (°=) and the brittle intermetallic phase Cu31Sn8