When appearances are deceptive – Louis Armstrong and the chemical removal
Before the first note reaches the ear, the eye catches sight of the fascinating metal gleam of the instrument. Brass, copper and silver are the metals which give the brass instrument its body and function.
In order to preserve this impressive metal sheen the instrument-maker must apply a protective coating after polishing. Without sealing it, the instrument would lose its lovely appearance in a very short time.
Hand sweat and fingerprints combined with oxygen and moisture in the air lead to a blemished patina on the surface of the instrument, which is more reminiscent of something found in an attic than a precious instrument.
And yet one occasionally sees musicians who appear with instruments marked with a conspicuous patina.
The existing or missing protective coating leads to nuanced changes in vibrational behaviour and sound characteristics. Only the practised musical ear can really hear these subtleties, though the altered sound character of the instrument can also be perceived by an untrained listener – perhaps subconsciously.
The choice of the chemicals used to remove coating and the necessary temperatures must be made very carefully and requires experience and specialist knowledge, to avoid damage to the sensitive surface of the instrument. The choice of the appropriate process varies from instrument to instrument and depends on the protective coating and materials used.
As a rule this chemical removal of coating takes place by means of a dipping process in our dip-stripping appliances, purpose-built and mostly small but effective.
Whether Louis Armstrong had to use this technique is left to our imagination.