I did laugh when I saw the Cossor advert from the late 1920's and pictured below: -
Just look at these fateful words, "......His clutching thieving fingers cannot harm this new Cossor...." For those who are wondering why this bumbling prose has tickled my pique, its because I was once accused of having clutching thieving fingers!@#$%! Alas my career in radio crime didn't take off and I did have ambitions of cat burgling an Enigma machine but I don't have a head for heights and besides, Enigma heists are passe as they have been done before. Anyhow, enough waffle so lets move on to other aspects of this Cossor advert.
Remember, this is from the early days of the "dull emitter" valve in which nickel wire was treated with successive layers of Barium admixtures to provide a viable emissive coating. Unfortunately, with multiple heating cycles, the emissive coating could flake and break away which reduced the emissive properties of the coated filament and if this wasn't enough this led to hot spots in operation due to localised overheating of the nickel substrate which changed it's crystallinity, ductility and tensile strength leading to multiple failure modes such as sagging and filament breakage.
The famed "kalenisation" process refers to a surface active adjunct that was added to the emissive coating to make it stick better. The aetiology of the name is from the china clay that was this mystery adjunct - you may know it as Kaolin,which was named after the hill in China (Kao-ling) from which it was mined for centuries.