Syahi

Syahi (also known as gaab, ank, satham or karanai) is the tuning paste applied to the head of many South Asian percussion instruments like the dholki, tabla, madal, mridangam, khol and pakhavaj.

Syahi is usually black in colour, circular in shape and is made of a mixture of flour, water and iron filings. Originally, syahi was a temporary application of flour and water. Over time it has evolved into a permanent addition.

Syahi functions by loading only a portion of the stretched skin with weight. In the higher-pitched (usually right-hand) drum (for instance, the tabla proper) this has the effect of altering the resonance frequency of some lower order vibrations more than others. The action on the left hand drum is a little different. On other side (for instance, the bayãn in the tabla), its position is offset and serves simply to lower the resonance frequency.

The application of the syahi is very involved. It starts with a base layer of mucilage, followed by the application of numerous thin layers of syahi masala (flour, water, iron filings and other secret ingredients), which are then rubbed with a stone. Not all of the layers are the same size. But the final product is expected to exhibit a specific shape.

The stone abrasion is crucial to creating the syahi. The material from which the syahi is made is inherently inflexible; if it were simply applied in a single layer and allowed to harden, it would not allow the drum to vibrate freely. The process of rubbing or polishing with the stone creates a tight latticework of cracks which extend down to the very base of the syahi, allowing the skin to resonate freely, despite the inherent inflexibility of the syahi's.

The process from the application of the first layer of glue and the finesse in adding the subsequent layers of syahi is the main determinant in the resulting tonal purity of the instrument and also of the longevity of the layers.

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Wikipedia