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The Making of Ebonite - Hard Rubber

A freshly delivered batch of Coutchuk. First Quality, X1, is needed to get the best results. P1070795.JPG Sulfur Powder. The first round of ebonite production - Furs made from caoutchouc, sulfur and linen oil. The autoclaves will shortly be shut, then slowly heated up to 152 degress. Adding a pressure of xxx atm. will induce an exothermic reaction which vulcanizes the rubber into Ebonite. The first round of vulcanization - caoutchouc, pure linen oil and sulfur mixed into pale yellow furs loaded into the 18 m long autoclaves. The yellow furs now are turned into shiny black hard rubber - but this first round is only meant to be ground to ebonite powder. The second round of mixing and vulcanizing will produce the high quality hard rubber. The black sheets crushed into particles of 3 mm diameter. P1070812.JPG These 3mm parts are being crushed between these two large iron rolls to become Ebonite Powder. P1070813.JPG Rubber powder all over.......... The ground hard rubber powder is now being filtered to achieve the finest possible ebonite powder. Here is where the Samples of Here is where hard rubber dust and caoutchouc are being mixed to be then made into black hard rubber. P1070850.JPG P1070853.JPG The Extruder - the soft rubber mix in here is being compressed, to shape into rods, but more important - to become homogenous and absolutely free of air. A difficult task especially regarding marbled material. Long periods of extrusion grant perfect consistence, but to get a wonderfully marbled rod with lots of contrast it needs a shorter period. Freshly extruded rods, still soft, ready to be pushed into the iron tubes. Every single rod diameter needs a set of tubes with diameter just a tiny bit bigger. 2 still soft red rods, which will become coral red after vulcanization. Heat and sulfur attacks the organic pigments - in the end, the bright colors seen here exit drastically changed. Its a magic science to know in advance, which color in the beginning produces which color in the end. On top of it - changes in extrusion tecnique, changes in climate outside - winter or summer - will always slightly vary results. P1070857.JPG P1070855.JPG P1070856.JPG Soft Talkum all over - every freshly extruded rod has to be covered with talkum to keep them separately. A refused rod of extruded rubber mix. You have to thoroughly clean the iron tubes before reloading for another round of vulcanizing. Here you see how the agressive environment of heat and sulfur slowly reduces the machinery to rust. P1070845.JPG P1070846.JPG Sulfur quickly attacks the iron rods, in which the hard rubber rods are being vulcanized. These sheets carry the rubber inside the autoclaves. Sulfur and heat attacks the iron and produce flakes of rust all over. 6 autoclaves in a row, each 18 meters long. This machine polishes the rough rods to precise diameter. Stock of large diameter black hard rubber. Colored rods. Ebonite rods of extra large diameter - used to produce sealings in the industry. Such a rod of about 90 mm in diameter needs two rounds of vulcanization - each 72 hours. Imagine the energy needed to keep up 152 Degrees celsius for such a long period of time. Some new colors and patterns. It was hard NOT to grab one of these to bring home into the workshop. Even more colored rods. To produce Coral red is an extra challenge - the legendary coral red hard rubber of the 20ies was made using anorganic pigments - often loaded with cadmium and other toxic metals. (Thus - you better not eat your Duofold Parker...) - Ebonite nowadays is made using organic fully non toxic pigments. Its not only rods of ebonite - this polished sheet of black hard rubber can be used to produce flat product like guitar picks. P1070863.JPG
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