ENAMELLING. 



same cautious management of the fire, 

 are to he repeated for every additional 

 coat of enamel the nature of the work 

 may demand. 



As soon as the number of coatings are 

 sufficient, it becomes necessary to give 

 an even surface to the enamel, which, 

 though polished by the fire, is neverthe- 

 less irregular. This is done with a fine 

 grained Lancashire tile and water. As 

 the file wears smooth, sand is used. 

 Much precaution and address are requir- 

 ed in this part of the work, not only be- 

 cause it is easy to make the enamel se- 

 parate in splinters t'rom the metal, but 

 likewise because *he colour would not 

 be uniform, if it were to be ground 

 thinner at one part than at another. 



The deep scratches of the file are in 

 the next place taken out by rubbing the 

 surface wiih a piece of deal wood and 

 fine sand and water. A polish is then 

 given by a second ignition. This polish, 

 however, is frequently insufficient, and 

 not as perfectly uniform as the delica- 

 cy of the work may require. 



The substance used by the enamellers 

 as a polishing material is known by the 

 name of rotten-stone, which is prepared 

 by pounding, washing", decanting ott the 

 turbid water, suffering the tine suspend- 

 ed particles to subside from this water, 

 and lastly levigating it upon a glass plate. 



The work is then cemented to a 

 square piece of wood, with a mixture of 

 resin and brickdust, and by this means 

 fixed in a vice. 



The first operation of polishing is 

 made by rubbing the work with rotten- 

 stone upon a small straight bar of pew- 

 ter. Some delicacy is here required, to 

 avoid scratching or producing flaws in 

 the enamel by pressing too hard. In 

 this way the piece is rendered perfectly 

 even. But the last brilliant polish i,s 

 given by a piece of deal wood and the 

 same rotten-stone. 



This is the general method of applying 

 namel ; but some colours require more 

 precaution in the management of the 

 fire. Opaque colours require less man- 

 agement than the transparent. A variety 

 of circumstances must be attended to in 

 transparent colours ; every colour re- 

 quires gold of a particular fineness. 



When different colours are intended 

 to be placed beside one another, they 

 are kept separate by a small edge or 

 prominency, which is left in the gold for 

 that purpose, and is polished along with 

 the enamel. 



The enamelling upon silver is effected 



nearly in the same manner as that of 

 gold; but the changes tusiaineU by the 

 colours upon silver by tne cuun of the 

 fire are much more considerable than 

 when gold is used. 



Copper is not much used by enamel- 

 lers, on account of the difficulty which 

 attends the attempt to fix beautiful co- 

 lours upon it. When this metal is used, 

 the common practice is, to apply a coat- 

 ing of opaque white enamel, and upon 

 this other colours which are more fusi- 

 ble than the white. 



A good effect is produced in toys by 

 leaving part of the gold bare. For this 

 purpose its surface is cut into suitable 

 compartments by the engraver. This, 

 however, is an expensive method, and is 

 for this reason occasionally imitated, by 

 applying small and very thin pieces of 

 gold upon the surface of the enamel, 

 where they are fixed by the fire, and af- 

 terwards covered by a transparent vi- 

 treous coating. 



A method of taking off the enamel 

 from any toy, without injuring the metal- 

 lic part, is often a desirable object. For 

 tliis purpose a mixture of common salt, 

 nitre, and alum in powder, is applied 

 upon the enamel, and the piece is put 

 into the furnace. As soon as the fusion 

 has taken place, the piece is to be sud- 

 denly thrown into water, which causes 

 the enamel to fly oft' either totally or in 

 part. Any part which may still remain 

 is to be removed by repeating the same 

 operation a second time. 



To coat vessels of iron or copper for 

 culinary purposes with an enamel capa- 

 ble of defending the metal from the ac- 

 tion of any solvent, and for enduring any 

 heat, or transition from heat to cold, ap- 

 pears a desirable object ; and many ex- 

 periments have been made on the sub- 

 ject by Mr. Soen Rinman of the Royal 

 Academy of Stockhlom. 



The following compositions he found 

 answer very well on copper. 1. The 

 white semi-transparent fluorspar and sul- 

 phate of lime, in equal quantities, pow- 

 dered, mixed, and calcinated in a white 

 heat ; then powdered, made into a thin 

 paste with water, and applied a little 

 warm to the vessel, also warmed. Then 

 dried and heated gradually to a certain 

 point, a very strong heat, greater than 

 is generally obtained in an assaying fur- 

 nace, is to be applied as quickly as pos- 

 sible. 2. Sixty parts of lime, one hun- 

 dred of flnor spar, sixty of gypsum, 

 twenty of quartz, and one of manga- 

 nese, are calcinated, ground, and applied 



