Partial Embedding Technique for Replication of Fibres 



283 



a bundle with a diameter of at least half of the size 

 of a fibre, but even then we could not clearly visua- 

 lize the size and shape. 



By shadowing the paper with metals such as gold 

 it was possible to see the fibrils themselves and the 

 membrane-like fibrils which have already been re- 

 vealed by the phase contrast microscope in previous 

 investigations. 



With the aid of the X-ray microscope it is also 

 possible to study coated papers and metal lamina- 

 tions. Coated papers, art papers and machine- 

 coated papers are provided on one or both sides 

 with a layer composed of a pigment, e.g. CaCOg or 

 kaolin, and a binder, e.g. starch or casein. The 

 filler of the layer can be distinguished very easily 

 from the cellulose fibres and the place of the pig- 

 ments in the layer is clearly seen. 



In particular titanium oxide and clay gave con- 

 trasts better than those obtained with calcium carbo- 

 nate. There is no possibility of removing fillers by 

 cutting cross sections with the aid of a microtome 

 knife. This is often the case with the techniques used 

 so far. In the microscopical slides frequently much 

 loading substance is present outside the sections. 



In case of laminations the punctures in the layer 

 appearing when the metal at that spot is too thin 

 were seen as bright pits in a grey field. 



The magnifications used in these investigations 

 are low, mostly ranging from 17 to 20 times. Higher 

 magnifications may be applied with success e.g. 

 when the size, shape and distribution of fillers must 

 be examined. In that case a high resolution of the 

 microscope is necessary. When studying the network 

 of the fibres a low magnification is sufficient. 



On account of the results obtained in our investi- 

 gations we consider the X-ray microscope a useful 

 instrument for the study of the structural details 

 of paper. 



In comparison with the methods used up to now 

 in this field the X-ray microscopical technique shows 



some advantages which we can summarize as follows. 



(i) The three-dimensional paper structure can be 

 examined without any disturbance of the links 

 between fibres and fillers. 



(ii) The paper can be studied in its whole thickness 

 without any refocusing of the microscope. It is 

 possible to get an impression of the fibres and 

 fillers situated in front as well as in the backside of 

 the paper in one picture. The reconstruction of the 

 structure of the paper from serial sections in the 

 normal light microscopical techniques is not neces- 

 sary. 



(iii) Stereomicrographs can be obtained in a simple 

 way. Consequently it is easy to study the whole depth 

 of the paper. This results from the great depth of 

 focus of this technique as compared with the focus 

 of the normal microscope. 



On account of these advantages it will be useful 

 to improve this method. 



In the first place the resolution of the microscope 

 must be at least as high as the resolution of the 

 normal light microscope. 



In the second place it will be necessary to raise 

 contrast in such a way that even the finer fibrillations 

 are clearly visible in the image. It is recommendable 

 to use for this purpose a chlorine zinc iodine solu- 

 tion instead of the alcoholic iodine solution used so 

 far. It is possible that also some use of contrast may 

 be obtained by using different targets and adopting 

 the target to the chemical nature of substance under 

 investigation. This will be valuable when examining 

 the loading substances. 



In the third place it is necessary that the exposure 

 time is fairly low. 



References 



1. VAN Nederveen, G. and Isings, J., Tappi 37, 103 (1954). 



2. Pelgroms, J. D., Paper Trade J. 134, No. 1, 25 (1952). 



Partial Embedding Technique for Replication of Fibres 



J. Dlugosz 



British Rayon Research Association, Manchester 



When the surfaces of textile fibres are studied with 

 the transmission electron microscope there is fre- 

 quently a need for a routine method for their repli- 

 cation since the number of different fibres submitted 

 for examination may be considerable. 



As the thickness of a textile fibre is usually greater 

 than 10 // it is difficult to make a replica which will 

 retain, after the necessary manipulation, the geomet- 

 rical shape of the fibre even supposing that the 

 replica film can be freed from the fibre. For these 



reasons it is convenient to restrict the surface of the 

 fibre to be replicated to such an extent that the 

 resulting replica will be fairly Hat. 



This can be achieved by the partial embedding 

 of the fibre in some medium to a controllable depth. 

 Less than half of the fibre should emerge from the 

 medium. 



A method designed to fulfil these two requirements 

 i.e. the ability to control the depth of embedding 

 and to embed in one preparation a large number of 



