514 PARCHMENT, VEGETABLE 



woolly side of a lambskin. But great care must be taken not to fray the surface ; a 

 circumstance of which some manufacturers are so much afraid, as not to use either 

 chalk or lime in the polishing. Should any grease be detected upon it, it must be re- 

 moved by steeping it in a lime-pit for ten days, then stretching it anew upon the 

 herse, after which it is transferred to the scraper. 



This workman employs here an edge tool of the same shape as the fleshing-knife, 

 but larger and sharper. He mounts the skin upon a frame like the herse above 

 described ; but he extends it merely with cords, without skewers or pins, and supports 

 it generally upon a piece of raw calfskin, strongly stretched. The tail of the skin 

 being placed towards the bottom of the frame, the workman first pares off, with a 

 sharp knife, any considerable roughnesses, and then scrapes the outside surface 

 obliquely downwards with the proper tools, till it becomes perfectly smooth : the 

 fleshy side needs no such operation ; and indeed, were both sides scraped, the skin 

 would be apt to become too thin, the only object of the scraper being to equalise its 

 thickness. Whatever irregularities remain, may be removed with a piece of the finest 

 pumice-stone, well flattened beforehand upon a fine sandstone. This process is per- 

 formed by laying the rough parchment upon an oblong plank of wood, in the form of 

 a stool ; the plank being covered with a piece of soft parchment stuffed with wool, to 

 form an elastic cushion for the grinding operation. It is merely the outside surface 

 that requires to be pumiced. The celebrated Strasburg vellum is prepared with 

 remarkably fine pumice-stones. 



If any small holes happen to be made in the parchment, they must be neatly 

 patched, by cutting their edges thin, and pasting on small pieces with gum-water. 



Parchment is coloured green only. The following is the process. In 500 parts of 

 rain-water, boil 8 of cream of tartar and 30 of crystallised verdigris ; when this solu- 

 tion is cold, pour into it 4 parts of nitric acid. Moisten the parchment with a brush, 

 and then apply the above liquid evenly over its surface. Lastly, the necessary lustre 

 may be given with white-of-eggs, or mucilage of gum arabic. 



PARCHMENT, VEGETABLE, or PARCHMENT PAPER. Vegetable 

 parchment is made from unsized paper, of which ordinary blotting-paper is an 

 example, and is well adapted for the process. This is manufactured from rags of 

 linen and cotton, thoroughly torn to pieces in the pulping machine, and it is found 

 that long-fibred paper is not so good for the production of vegetable parchment as 

 that which is more thoroughly pulped. The structure of the waterleaf may be 

 regarded as an interlacement of vegetable fibres in every direction, simply held 

 together by contact, and consequently offering a vast extension of surface and minute 

 cavities to favour capillary action. 



To make vegetable parchment, the waterleaf or blotting-paper is dipped in diluted 

 sulphuric acid when the change takes place, and though nothing appears to be 

 added or subtracted, the waterleaf loses all its previous properties and becomes 

 vegetable parchment. 



This very remarkable transformation is, however, a most delicate chemical pro- 

 cess. The strength of the acid must be regulated to the greatest nicety, for if on the 

 one hand it is too dilute, the fibre of the paper is converted into a soluble substance, 

 probably dextrine, and its paper-like properties are destroyed. If, however, the acid 

 be too strong, it also destroys the paper and renders it useless. 



For the most perfect result, the sulphuric acid and water should bo at ordinary 

 temperatures in the proportion of about two volumes of oil of vitriol and one volume 

 of water, and if the paper be simply damped before immersion, the strength of the 

 acid is altered at these spots, and the part so acted upon is destroyed. 



To make vegetable parchment, the waterleaf is dipped into the sulphuric acid 

 exactly diluted to the desired strength, when in the course of a few seconds the paper 

 will be observed to have undergone a manifest change, by which time the trans- 

 formation is effected in all its essential points. The acid has then done its work, and 

 is to be thoroughly removed from the paper, first, by repeated washings in water. 

 and subsequently by the use of very dilute ammonia to neutralise any faint trace of 

 acid which escapes the washing in water. All minute traces of sulphate of ammonia 

 left by the former process are removed as far as possible by further washings, and in 

 certain cases the infinitesimal trace of ammonia may be removed by lime or baryta. 



The action and intent of these several processes are to render the vegetable parch- 

 ment perfectly free from any acid or salt, and the object is thoroughly obtained in the 

 large way. 



"When the paper has undergone its metamorphosis, it is simply dried, when it be- 

 comes vegetable parchment, differing from blotting-paper, and possessing peculiarities 

 which separate it from every other known material. The surfaces of the paper ap- 

 pear to have undergone a complete change of structure and composition. All the 

 cavities of the waterleaf are closed, and the surface is solidified to such an extent, 







