Translation:Manufacture of artificial silk
MANUFACTURE OF ARTIFICIAL SILK
If every soldier carries a marshal’s baton in his knapsack, every chemist has a legendary million tucked away in a corner of their laboratory. Thus, there are many chemists. To claim this tempting fortune, countless researchers have dedicated themselves to creating a textile capable of rivaling silk; numerous studies have been pursued in this direction. One of the latest innovators, Mr. de Chardonnet, a former student of the Polytechnic School, appears to have succeeded. He has struck gold, and it is said he sold his process for precisely a million to an American company. We shall have even more chemists! This is a victory over politicians, who swarm in numbers yet produce little. Mr. de Chardonnet had set up a tiny artificial silk factory in the Machinery Gallery at the Champ de Mars. Visitors marveled as silk emerged from the machine before their eyes. It was in 1887 that Mr. de Chardonnet first presented his experiments to the Academy of Sciences. Since then, he has refined his process and succeeded in creating a textile from scratch that so closely resembles silk that an untrained eye could easily mistake it. Fabrics woven from this artificial silk shimmer like natural silk, boast an appealing appearance, and are often quite elegant. They would be a sensation for export. But on this point, let us yield the floor to Lyon’s manufacturers.
Mr. de Chardonnet uses raw materials such as cotton and sulfurous pulp from softwoods. This cellulose is treated with nitric acid, much like the process for making gun cotton. The resulting nitrated cellulose dissolves easily in alcohol and ether. The solution is then spun into fine threads. According to the inventor, the continuity of the thread, its transparency, play of light, and silky sheen can only be achieved by spinning a liquid solution. The solution is spun like collodion (a nitrocellulose mixture) and then partially stripped of its nitric acid. Here’s how the process works in practice: The cellulose is dissolved at a concentration of 6.5% in a mixture of 38 parts ether and 42 parts alcohol. The collodion is placed in a tin-lined copper reservoir, where an air pump maintains pressure of several atmospheres. At the base of the reservoir is a manifold fitted with vertical glass tubes, each ending in a capillary tip. A second tube surrounds each of these and receives a flow of water through a lateral pipe. This water circulates around the tubes connected to the reservoir and drains away very slowly. Under pressure, the collodion flows from the reservoir, exits through the capillary openings, and solidifies instantly upon contact with the water, emerging as a thread. A mechanical clamp automatically grasps the thread and winds it onto rotating bobbins. The threads are gathered into a raw-silk-like bundle, and the skeins are processed similarly to cocoon silk.Next, the denitration process is carried out simply by immersing the material in water containing diluted nitric acid at temperatures between 35°C and 25°C. The material becomes gelatinous and readily absorbs dyes and salts. At this stage, the threads lose all explosive properties. They can even be made non-combustible by soaking them in ammonium phosphate after the bath. This artificial silk thus becomes less flammable than cotton. The density of artificial silk is 1.40, placing it between that of raw silk (approximately 1.06) and processed silk (around 1.43). The breaking strength ranges from 25 to 35 kg per square millimeter. In comparison, raw cocoon silk has a breaking strength of 30 to 45 kg/mm², while processed silk averages about 25 kg/mm². Elasticity—defined as elongation before rupture—is comparable for both types of silk. As for luster, the new textile reportedly surpasses the brilliance of cocoon silk. Artificial silk is said to dye as effectively as natural silk, and it is even claimed to be the only fiber that behaves so readily in dye baths.
At the Trocadéro, in the forestry pavilion, another inventor showcased what he called 'French silk'. This too involves pyroxylin or trinitrated cellulose, but this time dissolved in crystallizable acetic acid with a small amount of gelatin added. Mr. de Chardonnet had experimented with this preparation method but abandoned it, finding the resulting thread brittle and prone to breaking. Mr. du Vivier claims to achieve the opposite result. Similar combinations had previously been tested to produce filaments for incandescent lamps. In any case, the samples we observed reportedly possess a luster superior to natural silk and a tenacity, it is asserted, only slightly inferior to silk. The inventor uses cellulose derived from black poplar cotton or boxwood, which is reduced to an impalpable powder and subjected to standard nitric acid treatment.
In both processes, the production cost of artificial silk is said to be very low—around 5 to 6 francs per kilogram.