The pads on woodwind instruments must be airtight. That is, really airtight. Touch a particular note for the duration of a semiquaver. If the seal is less than perfect, that note won't speak easily. Squawks, gurgles or silence can result. The tiniest, most trivial, leak makes playing difficult. Big leaks sabotage performance completely.
Instrument repairer Eddie Ashton has a convincing way of displaying and measuring how much an instrument leaks. Using a lump of Bostik Blu Tack and a rubber tube, he fits a vacuum gauge to the instrument. He then pops another rubber tube into his mouth, sucks the air out, then reads off how good a vacuum he can create. Next, he stops sucking, blocks the bore with his tongue, and notes how long the vacuum lasts. Surprisingly, even new instruments are far from perfect.
Cynics will point out that this test is applied in the wrong direction. A woodwind instrument is never required to hold a vacuum. This is one of the many challenges with maintaining and fixing wind instruments. As here, matters are often concluded with the observation: "Well, it's the nearest we can get."
According to Ashton, leaks can sometimes occur because of tiny cracks in the wood, or even because key support holes drilled 'blind' into the body of the instrument can penetrate a fraction too far. Air escapes from what is, visibly, an imperceptible hole. End grain that is open inside the tone holes - at the 'top' and 'bottom' sides of the hole - can also be leaky. But the biggest loss of air comes from the pad itself.
"A conventional pad is made by stretching a piece of skin over and around a disc of felt, then securing it on the underside. In use, the felt acts as a resilient cushion,' explains Ashton. Because of condensation from the player's breath, pads endure constant wetting and drying. They are operated by a mechanism mounted onto the wooden body of the instrument, itself subject to movement as the timber responds to atmospheric changes. The key mechanism is - in engineering terms - fairly crude, to keep the cost and the weight down. "It's probably got lousy loose bearings, which means it doesn't come down in the same place twice," says Ashton. Considering these variables, and a dozen more, it's not surprising that air escapes.
Ashton gives a second convincing demonstration. This time he places the blade of a screwdriver gently onto the surface of a conventional pad. Where the screwdriver touches the pad surface, the skin (and the supporting felt) sags, similar to the way that the mattress of a bed gives way when you press it with your hand. The surface distorts. This is what happens to a traditional pad when it meets any imperfection. The pad distorts over a wider area.
Next, Ashton takes another pad, one made from a black plastic material backed with cork. He places the blade of the screwdriver on its surface, again pressing gently. The blade sinks into the surface. But this time the surrounding material doesn't move. Ashton puts it succinctly: "Adjacent places on the face of the pad are unaffected by each other, allowing microscopic inaccuracies of the tone hole to be accommodated." This black plastic material (which is of a cellular structure, like a very thin sheet of tiny bubbles), and the way it is fitted, are the twin secrets of Superpads.
Eddie Ashton lists the advantages: "The pads are compliant enough to be forgiving yet firm enough to be accurate. They're very quiet. They're impervious to moisture yet don't encourage clogging. They are exactly the same consistency from the centre to the outside edge."
About the second secret of Superpads - the method of fitting - Eddie Ashton is saying very little, beyond admitting that the black plastic, which is fixed to a cork base, is the simple part of his improved pads. "The clever bit is the unique way by which the pads are set in the key. That ensures that each one is perfectly positioned without any application of force, and regardless of key orientation with its tone hole," he says. About the source of the black plastic (it's a type of neoprene) he reveals nothing, except to say that he came across it by accident. The manufacturing process means that this material is the thinnest of its type that can be made.
Are there any disadvantages? Well, the pads are black, and some players don't like the colour. There's an element of tradition in this preference: pads have always been either white or brown. But woodwind pads are largely invisible, only being seen by people within three or four metres of the player, at most. So the colour is insignificant. There is a second disadvantage: "They are so good that you won't believe it," claims Ashton, with a smile.
After eight years of production, there is now a healthy number of professional woodwind players who have had the pads fitted. A photo gallery in the Cadishead, Manchester, shop that Eddie Ashton runs with his brother Don is testimony to having won over these most conservative of musicians.
The most telling development is the number of approaches now being made by other clarinet makers and repairers. Eddie Ashton can recount several tales of amazingly shady offers and the proffering of unfair deals. But that's another story.