[en]LIGHTenment Journey.

 

May 7th, 2026. You are invited to participate to the [en]LIGHTenment Journey.

Location: United States

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About the Cyanotype process.

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Cyanotypes. Photochemical blueprinting (also known as cyanotype process , from the Greek kyanos-blue) is one of the historically oldest photographic techniques that produce intensively blue pictures. Today it is classified as the member of a family of alternative photographic processes. This process was developed in 1842 by the English natural scientist and astronomer Sir John Frederick Herschel (1792-1871). Cyanotype was thus the third photographic technique after daguerrotype and talbotype (calotype), with which stable photographic pictures could be obtained. Unlike previous silver-based techniques, cyanotype is based on the light sensitivity of iron(III) complexes, which makes it comparatively inexpensive. Herschel himself is the author of today’s common expressions such as negative, positive, photograph and snapshot. Figure 1: Sir John Frederick Herschel, English astronomer, mathematician, chemist and pioneer of photography, especially the cyanotype The intensive blue color of cy...
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About the phenomenon of Chemiluminescence.

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Chemiluminescence is the emission of cold light as a result of a chemical reaction. In a chemiluminescent reaction, reactive intermediates are formed which enter electronically excited states. Subsequent transition back to ground state is accompanied by a release of energy in form of light. The mechanism is depicted in Fig. 5. Fig. 5: Scenarios of a chemiluminescent reaction Compounds A and B react together forming C* and D while C* is in electronically excited or energetically rich state. C* can get rid of its extra energy by several pathways:Non-productive non-radiative transitions producing heat (undesirable process) Direct deexcitation of C* by a radiative transition with concomitant emission of light characteristic for C* Indirect deexcitation – C* transfers its extra energy to a a suitable fluorescer that can act as a temporary energy acceptor and then emit the energy in form of light. The emission spectrum is then dependent on the structure of fluorescer. This can be used with a...
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About the theory of Fluorescence.

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Fluorescence is a physical phenomenon during which a material is electronically excited by absorption of a quantum of electromagnetic radiation and subsequently emits light. Fluorescence represents a subcategory of cold-light emission – luminescence. The origin of fluorescence is related to the material´s ability to absorb electromagnetic radiation and subsequently release the extra energy in form of a characteristic emission radiation. The irradiated material enters a so called high energy “excited state”. The return from the excited state to the ground state is linked to the emission of a photon. When this happens instantly (<10-8 s), we speak about fluorescence. The wavelength of the excitation radiation is almost always shorter (and therefore higher in energy) than the emission radiation. (There are only very few exceptions to this rule).The typical examples of the excitation radiation are light in UV region, visible light, X-Rays and radioactivity. In the latter case we speak ...
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