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Watch hand luminous paint9/1/2023 ![]() ![]() ![]() This phenomenon, called phosphorescence, has a maximum duration of five or six hours, a performance clearly lower than that guaranteed by the self-produced luminescence paste. The induced luminescence paint does not have an autonomous source of energy, in fact it needs to receive a “charge” from the outside in the form of normal daylight charge that gradually diminishes as it transforms into released luminescence. The natural consequence was that, starting from the sixties, a new substance was introduced, Tritium, a paste with induced luminescence. Suffice it to say that the Panerai Radiomir of the 1930s needed a “reclamation” before being exhibited in the museum of the manufacturer in Florence. They were exposed to amounts of radium that no watch owner experiences simply by wearing it on their wrist, however, watches with radium luminescent paste remain dangerous. To give an idea of the harmful potential of the substance, just think that in the Thirties, the Radium Girls, the Radium Girls, working closely with the luminescent paste, licking the brushes with which they applied the paint to numbers and hands, to making them more pointed, they contracted serious illnesses that led to many of them to death. However, this did not apply to the workshop workers who worked on the open watch and in particular came into contact with the luminous material. The watches were relatively safe for the wearer, as the radiation emitted by radium into the air is only a few centimeters and is contained by the watch case itself. It was the First World War that helped to ensure a high demand for watches whose brightness was independent of light, such as the Panerai Radiomir supplied to the Italian Royal Navy until the Second World War. Radium is a highly radioactive chemical element with a half-life, that is the time required for the radioactive emission of a given quantity of material to be halved, of 1600 years. Guido Panerai, Italian pioneer in the field of optics and watches, was the first to patent, in 1914, a phosphor called “Radiomir”, in which the energy produced by the radioactive decay of radium bromide is stimulated by zinc sulphide, thus causing the fluorescent substance to glow permanently. The discovery of radioactivity by Marie and Pierre Curie started the use of self-produced luminescence, but it was the discovery of Radio in 1898, already known for its self-luminous properties, that opened up the application of these materials. The self-produced luminescence was, for most of the twentieth century, the preferred choice by manufacturers, its main feature, and its strong point, is that the watch does not need to be exposed to light to activate the luminescence the light emission is determined by the interaction between the two components of the luminescent paste, a radionuclide and the scintillator.Īlthough at this point we could risk getting lost in the details of chemistry, it is enough to know that a radionuclide is a radioactive atom that, when decaying, emits energy in the form of radiation, while the scintillator receives the radiant energy from the radionuclide and converts it into visible light emission. The first experiments: self-produced luminescence We can divide the types of luminescence into two broad categories, self-produced luminescence and induced luminescence. Since the beginning of the 20th century, the advantages and disadvantages of various chemical methods have shaped how luminous materials are applied to watches yes because a watch shines in the dark thanks to luminous materials, more commonly called “lume”, which are typically found on the dial, on the hands and sometimes on the bezel. Electricity was not that widespread and therefore there was a need for watches that would indicate the time even in difficult light or visibility conditions. Nowadays, finding real darkness is difficult also due to the strong light pollution of our environment, but in the past centuries the reality was different. ![]()
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