Early 19th century square and grand pianos typically use a keyboard cloth that is about 1.5mm thick applying two thicknesses to the back-touch and front rail of the keyframe and one thickness to the balance rail. One or two thicknesses of cloth are used on the hammer rail.
The two images above show a keyframe from an 1812 Broadwood grand piano where the new cloths have been applied. A single thickness of the high quality 2.5mm cloth has been used on the back-touch and front rail and a single piece of the former quality of 1.5mm cloth on the balance rail. It is important that whatever cloth are used, the correct amount of key dip is achieved. For this instrument it is about 7.5mm and this has been achieved with this arrangement of cloth. The 2.5mm cloth is about twice the thickness of the original cloth and therefore it is a good choice in place of two thicknesses of the thinner cloth. The 1.5 mm cloth is used on the balance rail because the 2.5mm cloth would be too thick. The balance rail cloth has been cut in a single castellated piece as it would have been originally, but individual bushings can be cut instead. A high quality 1.5mm cloth is planned for production in 2020.
18th century square pianos may have a different arrangement and typically a single piece of cloth is used in front of the key lever guide pins of the naturals over one piece of veg-tanned leather and for the sharps, individual leather rectangular pads, often covered in cloth, used in front of each key lever guide pin. The thickness of the cloth used would be about 1.5mm but in some early square piano, the thickness may only be about 1.0mm. Part of the keyframe from a 1777 Christopher Ganer square piano is shown below with this arrangement. In this instance, the pads for the sharps are not covered in cloth and the cloth on the balance rail is not castellated.
A typical single action square piano would normally only use a single piece of cloth on the front rail. It is important that the amount of compression of the cloth is limited to avoid the hammer blocking on fortissimo and not reaching the string on piano playing and therefore it would be unusual to find two thicknesses of cloth. The 2.5mm cloth is unsuitable for use on 18th century square pianos.
Early pianos use the front rail as a stop for the travel of the key levers. Some examples also have a secondary stop above the back of the key lever. Harpsichords and spinets may use the jack rail as the stop with a secondary stop at the front rail. The 2.5mm high quality cloth is suitable for this application possibly using more than one thickness.
Where cloth are glued in place such as the hitchpin cloth, it is best to use Seccotine fish glue for this purpose rather that hide glue to limit the risk of the glue bleeding though the cloth.
If you are restoring or building several instruments it is best to buy the cloth off the roll by the metre and having both the 2.5mm and 1.5mm cloth provides the flexibility to build exact thicknesses as required.
More information about the new high quality 1.5mm cloth will be given when available. For further information about any of the cloths please contact Graham Walker using the Contact form.