RESINOGRAPHY 



'—Tread 



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^ ^ *#.iG 



P^eaker Stock 

 Breaker Cord 



Cushion Stock 



— Carcass Cord + Stock 



Fig. 13. A cross-section of an automobile tire of unknown manufacturer. The section, cut with a wet 

 razor blade, was photographed by oblique, reflected light. Shows the kind, numbers and distributions 

 of the layers and indicates places to sample for identification of the kinds of rubbers and fibers. 



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Fig. 14. Natural rubber tire tread stock filled 

 with carbon black (shown as black round areas 

 and also as commensurate depressions and eleva- 

 tions). An electron micrograph of positive replica; 

 no shadowing metal. Matrix also manifests tiny 

 rubber particles of Type 1(7). 



this wa}^ (Figure 3). Cellulose esters (e.g., 

 collodion) and some vinyl polymers (e.g., 

 "Formvar" polyvinyl acetal) meet the require- 

 ments so well that they are used as replicat- 

 ing media. Gelatin, polyvinyl alcohol and 

 cellulose ethers are hydrophilic and are used 

 as replicating media when organic solvents 



are detrimental. These organic replicating 

 media and substrates are high polymers and 

 as such they could manifest particulate 

 texture as large as that of the specimen. 

 Instead, carbon, silica and other inorganic 

 replicating media should be considered. 

 With any replicating medium or substrate, 

 "blanks" should be run. For similar reasons 

 "blanks" should be run on all photographic 

 materials. 



The general techniques of electron mi- 

 croscopy and replication are described in 

 detail elsewhere in this encyclopedia, and 

 limitations as well as advantages of the 

 electron microscopy have been published 

 (2, 3). The specific advantage of the electron 

 microscope is that it makes visible prac- 

 tically all particles of Type II and significant 

 ones of Type I. The limitations are related 

 to the problems of representing the texture, 

 gaining sufficient contrast and avoiding 

 polymerization, scission or any other change 

 due to the electron beam or vacuum. 



There are also the general limitations of 

 resinography with respect to its infancy. 



536 



