I saw this post in MMD, (Mechanical Music Devices) about touching up nicks and dings in plates. I contacted the author for permission to repost. ---------------------------------------------------------------------------- - Thanks for the e-mail. Of course you may post my MMD comments to the Pianotech list—if you think they are of any interest or use! Just to explain where I'm coming from, I'm not a professional tuner or technician but I started piano lessons when I was four (about 46 years ago), got interested in fine instruments from the age of about 15, and I've been involved with rebuilding for over 30 years—particularly top name player pianos. I was fortunate enough to be given effectively a private apprenticeship by the late Lionel Box (died 1976 aged 86) who was Bechstein's top tuner/tech in London between the wars and Bösendorfer's in the 70s. In the 70s I was technical development and production manager at James Bourlet & Sons, the oldest and once the most famous picture framer and restorer. That post involved a lot of research and trials in restoration and manufacturing technology, and I learned an enormous amount, not just about gilding! I believe gesso for best adhesion to iron plates would need to have a greater proportion of glue to whiting and almost too much tallow but still only a very small amount. I have to say that I think a good quality water based vinyl/acrylic spackle would do as well and probably better today. Regards Patrick Handscombe Wivenhoe, Essex, UK. >>>>> From: prodiver@dircon.co.uk(Paddy Handscombe) To: Mechanical Music Digest <rolls@foxtail.com> Date: Sun, 25 Jun 2000 22:45:43 +0100 Subject: Filling & Gilding Cast Iron Piano Plates Many very well cast piano plates (frames) here in Europe seem not to have been filled, just primed, before gilding, but the filler of choice certainly before WW1 seems to have been gesso (pronounced jess-oh), the same gesso used since time immemorial as the ground for classic English water-gilding of picture frames, furniture, etc., and sometimes as a 'stopper' for wood before finishing. There are as many recipes for gesso as there are gilders, but most list animal glue (non-crystallising), whiting (hydrated calcium sulphate powder) and tallow, simmered and stirred until creamy and applied hot. Best water gilding practice involves applying as many as eight coats, but piano plates probably had fewer. Properly-formulated gesso will stick to anything, but will crack if allowed to dry too quickly. When quite dry the surface is rubbed down to a perfect, almost polished finish. Then it can be stained, painted, lacquered, whatever. It is possible to colour liquid gesso, black for instance, by stirring in pigment. But traditionally, prior to real gold water gilding, two coats of red, yellow or black 'bole' (bolus), a fine clay suspension, are applied to the plain gesso, and the surface rubbed smooth again. Red is used for classic antique gilding, yellow for bright burnished finishes, and black often under silver leaf. The colour of the bole is significant since the leaf is so thin, and also not all classic gilding is intended to achieve perfect coverage. I have never seen black gesso or bole used on a piano plate; I suspect that areas of blackening occur through a harmless reaction between iron, humidity and calcium sulphate. In water gilding the substrate is wetted with a tincture of water, glue-size and alcohol just before each real gold or silver leaf is applied. Areas may be double-leafed for perfect coverage or durability. Finally the leaf may be highly burnished into the gesso with agate-tipped tools until it effectively becomes plate, or left matt. This is how Broadwoods double-gilt their plates, if at all, until about 1902. But for years they had reservations about gilded plates, feeling that, like veneered furniture, French polish and coasters, they were just too nouveau-riche. Even into the 1920s some Broadwood models had beautiful deep green painted plates and deep crimson stained sound boards. They also declined to put the name John Broadwood & Sons on the fall in brass, and certainly not with a decal, doing the job perfectly and discreetly in inlaid box or pear wood. Until 1914 some Broadwood instruments were still cased in solid, cross-laminated mahogany or walnut, and they were famous for their stunning 'steel Barless' pianos in painted or stained 'Arts and Crafts' cases designed by leading country house architects like Edwin Lutyens. Patrick Handscombe Wivenhoe, Essex, UK. <<<<<<<<<<<
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