3 CONCLUSIONS

Details contained in patents of the second half of the 19th century furnish useful information regarding the development of the first semisynthetic plastics. At that time, the means of producing them were entirely experimental, as the modern concept of the polymer did not exist until it was introduced by the German chemist Hermann Staudinger in 1920, and even then it was not fully accepted until 1930.

Yet, despite the lack of a firm scientific basis, researchers successfully improved the manufacturing process through chemical modification of the base biopolymer and the use of certain additives.

However, many of these materials were, as we now know, intrinsically unstable and were generally highly sensitive to ambient conditions (temperature, relative humidity, and light). This instability was due to the nature and proportion of the chemical groups (especially nitrate and acetate) of semisynthetic plastics embedded in the structure and to the presence of plasticizers. Such details are recorded in the patents, and therefore examination of these patents can be useful in cataloging artistic works or objects and in determining the measures best suited to their conservation.