![]() ![]() The removal of the tarnish and also of the soot left on the reflector from the lamp flame, when chimney-less lamps were used, caused the need for polishing the reflectors on a very frequent basis. Unfortunately silver oxidizes (tarnishes) rapidly leading to the need for continual polishing. A second construction method used heavy silver cladding, which was bonded to the copper to improve its reflective qualities. However, plain copper was not a very reflective surface and was soon abandoned. The copper reflectors were then polished to form a shinny surface to reflect the light. ![]() The sheets of metal were then formed into parabolic shapes by hammering into the mold, and still later, iron molds were used to create more refined parabolic reflectors. Later, wooden molds were carved by hand and checked against paper or brass templates. ![]() In the early method, a sheet of metal, usually copper, was fashioned into a crude parabolic shape by hammering a flat sheet using only the skill of the craftsman as a guide. Two general methods of construction were employed. The parabolic shape was very difficult to fashion by hand. Problems with the manufacture of reflectors kept them from reaching their theoretical capabilities. However, approximately 30 percent of the total available light escapes from around the edge of the reflector and is not concentrated into the beam. ![]() This concentrated beam of light can be directed to the horizon and can be manipulated to provide a very useful light for the mariner. Parabolic reflectors gather the light from the focus of the reflector and return it in a concentrated beam in the direction the reflector is facing. A spherical reflector will appear to intensify the brightness of the flame, but will not form the light into a concentrated beam useful to the mariner. Spherical reflectors return the light rays to the focus of the reflector where the lamp is placed. A flat plate reflector reflects light in many directions and only a small portion of the light is reflected forward in a direction useful to a mariner. Flat plate reflectors are seldom truly flat, nor are they always highly reflective. There are three basic types of reflecting surfaces, Flat, Spherical and Parabolic as shown in the drawing. Highly polished metal surfaces behave as mirrors, and when they are made in the shape of a parabola they concentrate the light from a light source placed in the focus of the parabola. Reflection occurs when a ray of light hits a painted or polished surface and is reflected from the surface. In this story we will discuss the various types of reflectors that were used to create the ‘Mirror of Light’. The first method of projecting and directing the light started with the design of the reflector. Experiments were made with the types of fuel being burned, with the design of the braziers, which held the burning fuel, and with ways to direct or concentrate the light from the fire. Lighthouse designers were constantly looking for ways to produce more light. The major problem with early lighthouses was the small output of light from the wood or coal fires then being used. What is Catoptric? It's from the Greek word (Catoptron) for mirror, or reflection, and the lighthouse illumination system based on the principle of reflection was given the name Catoptric System in English. This is a story about the Catoptric system of lighthouse illumination. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |