640 



GILDING 



till the saline crust which covers it becomes homogeneous, nearly transparent, and 

 enters into true fusion. It is then taken from the fire and suddenly plunged into cold 

 water, which separates the saline crust, carrying away even the coat of epargnc. 

 The piece is lastly passed through very weak nitric acid, washed in a great body of 

 water, and dried by exposure either to the air, over a drying stove, or with clean linen 

 cloths. 



7. Of or-moulu colour. When it is desired to put a piece of gilded bronze into 

 or-moulu colour, it must bo less scrubbed with the scratch-brush than usual, and 

 made to come back again by heating it more strongly than if it were to be deadened, 

 and allowing it then to cool a little. The or-moulu covering is a mixture of hematite, 

 alum, and sea salt. This mixture is to be thinned with vinegar, and applied with a 

 brush so as to cover the gilded brass, with reserve of the burnished parts. The piece 

 is then put on glowing coals, urged a little by the bellows, and allowed to heat till 

 the colour begins to blacken. The piece ought to be so hot that water sprinkled on 

 it may cause a hissing noise. It is then taken from the fire, plunged into cold water, 

 washed, and next rubbed with a brush dipped in vinegar, if the piece be smooth ; 

 but if it be chased, weak nitric acid must be used. In either case, it must be finally 

 washed in a body of pure water, and dried over a gentle fire. 



8. Of red gold colour. To give this hue, the piece, after being coated with amalgam, 

 and heated, is in this hot state to be suspended by an iron wire, and tempered with 

 the composition known under the name of gilder's wax ; made with yellow wax, red 

 ochre, verdigris, and alum. In this state it is presented to the flame of a wood fire, 

 is heated strongly, and the combustion of its coating is favoured by throwing some 

 drops of the wax-mixture into the burning fuel. It is now turned round and round 

 over the fire, so that the flame may act equally. When all the wax of the colouring 

 is burned away, and when the flame is extinguished, the piece is to be plunged in 

 water, washed, and scrubbed with the scratch-brush and pure vinegar. If the colour 

 is not beautiful, and quite equal in shade, the piece is coated with verdigris dis- 

 solved in vinegar, dried over a gentle fire, plunged in water, and scrubbed with 

 pure vinegar, or even with a little weak nitric acid if the piece exhibit too dark 

 a hue. It is now washed, burnished, washed anew, wiped with linen cloths, and 

 finally dried over a gentle firo. 



The following is the 

 outline of a complete 

 gilding factory, as now 

 fitted up at Paris : 



Figs. 1085, 1086, front 

 elevation and plan of a 

 complete gilding work- 

 shop. 



p. Furnace of appel, or 

 draught, serving at the 

 same time to heat the 

 deadening pan (potion au 

 mat}. 



F. Ash-pit of this fur- 

 nace. 



N. Chimney of this 

 furnace constructed of 

 bricks, as far as the con- 

 traction of the great 

 chimney, s, of the forge, 

 and which is terminal rd 

 by a summit pipe rising 

 2 or 3 yards above this 

 contraction. 



B. Forge for annealing 

 the pieces of bronze ; for 

 drying the gilded pieces, 

 &c. 



c. Chimney of commu- 

 nication between the an- 

 nealing forge H, and the 

 upace D below the forge. This chimney serves to carry the noxious fumes into tho 

 great vent of the factory. 



r. Bucket for tho brightening operation. 



A. Forge for passing the amalgam over the piece, 



108G 



