CHAPTER XIX 
NIELLO 
Theophilus—Cellini—Bolas—Spon. 

Niello is a composition of silver, lead and sulphur, or of other ingredients, used from early times for filling-in engraved patterns. The dark grey or black colour of the niello con trasts well with gold or silver. Cloisonne wire patterns are sometimes filled with niello, as on the Cross of Cong, in the National Museum, Dublin. 

Perhaps the earliest description of the manufacture of niello is that given by the eleventh-century monk, Theo philus. His treatises on gold-and silver-smiths' work, translated byRobert Hendrie, may be met with occasionally. He gives a delightful account of the manner in which he and other goldsmiths of his time did their work. In the chapters on niello, quoted below, he is describing the decora tion of a two-handled chalice (Book III, chapters xxviii, xxix, xxxii, and xli). 

" Take pure silver, and divide it into two equal weights, adding to it a third part of pure copper. vVhen you have placed these three into a cast metal cup, weigh as much lead as half of the copper which you have mixed with the silver weighs, and taking yellow sulphur break it very small, and put the lead and part of this sulphur upon a small copper vessel, and place the rest of the sulphur in another cast metal cup. And when you have liquefied the silver with the copper, stir it evenly with charcoal, and instantly pour into it the lead and the sulphur from the small copper cup, and again mix it well with the charcoal, and with quickness pour it into the other molten cup upon the sulphur which you had put into it, and then putting down the small vase with which you have poured out, take that into which you have cast it and place it in the fire until [the contents] liquefy, and again stirring it together pour into the iron crucible. Before this cools beat it a little, and warm it a little, and again beat it, and do this until it is quite thinned. For the nature of the niello is such that if it is struck while cold it is immediately broken and flies to pieces, nor should it be made so warm as to glow, because it instantly liquefies and flows into ashes. The niello being made thin, put it into a deep and thick cup, and pouring water upon it, break it up with a round hammer until it becomes very small, and taking it out, dry it, and put that which is fine into a goose quill and close it up, but that which is coarser place again in the vessel and bruise it, and being again dried, put it in another quill. 

" When you have filled many quills take the gum which is called parahas [borax] and grind a small piece of it with water in the same vase, so that the water is made scarcely turbid from it, and first moisten the place which you wish to blacken with this water, and taking the quill rub off the ground niello with a light instrument upon it carefully, until you have covered the whole, and do this over the whole. Then gather excessively hot coals [charcoal], and placing the vase in them carefully cover them, so that no coal be placed, nor can fall, over the niello. And when it is liquefied hold the vase with the pincers and turn it from every side on which you see it flow, and in thus turning it round take care that the niello does not fall to the ground. But should it not be completely perfect at the first heating, again moisten it, and superpose [niello] as before, and take great care that no further work is required. 

" When you have mixed and melted the niello, take a portion of it and beat it square long and slender. Then take the handle [of the chalice] with the pincers and heat it in the fire until it glows, and with another forceps, long and thin, hold the niello and rub it over all the places which you wish to make black until all the drawings [engraved 
spaces] are full, and carrying it away from the fire carefully make it smooth with a flat file until the silver appear, so that you can scarcely observe the traits and so scrape it with the cutting-iron, carefully cut away the inequalities, and you will gild what remains. . . . 

".. . . Scrape all the parts carefully which are blackened with the neillo, with the cutting instrument. Afterwards you have a black and soft stone, which can easily be cut and almost scraped with the nail, and with it you rub the niello, wetted with saliva, carefully and smoothly every where, until all the drawings are plainly seen, and it is quite smooth. You also have a piece of wood from the lime tree, of the length and thickness of the smallest finger, dry and smoothly cut; upon which you place this wet powder, which comes from the stone and saliva in rubbing, and with this wood and the same powder you rub the niello a long time and lightly, and always add saliva, that it may be wet, until it is made brilliant everywhere. Then take wax from the hollow of your ear, and when you have wiped the niello clean with a fine linen cloth, you anoint it everywhere, and with goat or hart's skin you will lightly rub it until it is made quite bright." 

Benvenuto Cellini, in his treatise on goldsmiths' work also described the making of niello. He used— 
Silver 1 part. 
Copper 2 parts.
 Lead 3„
 Powdered sulphur. 

The silver and copper were first melted together and the lead added to them. The crucible was then removed from the fire and the liquid metal stirred well with a piece of charcoal held in the tongs. The scum caused by the oxidisa tion of some of the lead was skimmed off, and the stirring proceeding till the three metalswere thoroughly blended. A narrow necked earthenware flask, about as big as the fist was half-filled with powdered sulphur. Into this the molten metal was poured. The mouth was closed with damp clay; and the flask, held in a piece of stout canvas, thoroughly shaken. When it had cooled, the flask was broken open, and the metal, which had now combined with the sulphur, was found in the form of little black grains. These were melted in a crucible with borax, cast into an ingot, and again broken up. This operation was repeated several times before the niello was considered to be properly mixed. 

Mr. Bolas, in his little book Etching on Metals, gives " an easily fusible niello" suitable for all kinds of work, large or small— 
Native sulphide of antimony, finely ground 2 parts 
Native sulphide of lead (galena), finely ground 1 part 
Sulphur in small fragments or powder 8 parts. 

These ingredients should fill less than half of a fireclay cruci ble. Heat gently and stir all the while with the stem of a pipe. If the mixture is overheated or not properly stirred it will become thick and stiff. When properly fused it may be poured out on a slab of stone. The niello is then coarsely powdered. 


A less fusible niello of finer black colour, and specially suitable for small articles in silver or gold, is described by Mr. Bolas. It is composed of— 
Silver 2 parts 
Copper 4 ,, 
Antimony 1 part 
Lead 1„ 
Sulphur. 

Melt the silver and copper together, add the autimony and lead, and cast into an ingot. Reduce it to powder by filing it with a smooth file. Mix the filings with twice their weight of powdered sulphur. Drop this mixture, a teaspoonful at a time, into a crucible maintained at a low red heat. Allow the crucible to cool, break it, and, with pestle and mortar, finely powder the black sulphide. Mix the powder with twice its weight of sulphur and melt it again. Then break up the niello—into small grains rather than to fine powder. 

The work should be thoroughly cleaned before the niello is applied. Mr. Bolas recommends that the final cleaning shall be with a stiff brush and some gritt}' powder, such as bathbrick dust,—care being taken to brush it all cut. Etched silver work should be rubbed with a fine wire scratch brush to remove any silver oxides which may have been left in the recesses. Fill all the hollows with the small grains of niello, and pile a little on top to make up for the smaller space which the fused material will occupy. Drop over it a little powdered borax,—very little. Heat the work until the niello melts, and at this time, go over it with a hot iron spatula (Mr. Bolas says, a pipe-stem made hot) to assist in completely filling the recesses. Be careful not to allow the work to get red hot, or even to remain hot for longer than you can help, or the lead, which is one of the components of the niello, will rapidly corrode the silver or gold of which the work is composed. If the work is not flat, the niello may be dropped into the recesses of the heated metal as it is turned aTbout, and worked into place with the hot spatula. Now remove any superfluous niello with a file. But before you have quite got down to the surface of your work, heat it again till it is rather too hot for the hand to bear, and with a steel burnisher and a little oil burnish well the surface of the niello. The object of this burnishing is to stop up any little bubble holes which may have come in the process, and which would otherwise spoil the surface of the work. Then scrape the surface of the work true and polish in the ordinary 
way. 

Spon gives—• 
First crucible—Flowers of sulphur 27 oz. 
Sal-ammoniac 2| „ 

Second crucible, which after fusion is poured into the first— 
Silver 1/2 oz. 
Copper l 1/2 „ 
Lead 2 3/4 „ 

Add a little sal-ammoniac to the mixture. Reduce to powder, mix with a small proportion of a solution of sal-ammoniac for use. Spread the niello on the work. Heat in a muffle till the composition solders to the metal. Polish level, as above.