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3. Note on the Black Lustrous Varnish of ancient Pottery. 
By John Davy, M.D., F.R.SS. L. & E., &c. 
So far as my reading extends, the nature of the black varnish of 
the ancient Greek and Etruscan vases is still undetermined. 
From the experiments I have made, operating on very small 
quantities, abraded from vases which were taken from tombs in 
the Ionian Islands, I have been led to the conclusion, that it is a 
vitreous matter, coloured by black oxide of iron, probably mixed with 
particles of metallic iron, to which its peculiar lustre may be owing. 
It is, I find, of the hardness of glass, brittle and opaque. In 
powder or small fragments, it is powerfully attracted by the magnet. 
Before the blow-pipe it is fusible, its colour remaining unchanged, 
however powerfully it may be urged by the flame. It is insoluble 
in the nitric and muriatic acids, and also in the nitro -muriatic, and 
without change of colour ; but, when fused with boracic acid, and 
then acted on by muriatic acid, its colouring matter is dissolved, 
siliceous matter remaining, and the solution is slightly precipitated 
by ammonia. 
Considering this glazing as a compound of silica and of an alkali, 
or of an alkaline earth, coloured by iron, it may, I presume, be in- 
ferred, that it was applied to the earthenware in the form of a paste, 
and that the vessels were afterwards subjected to a temperature 
sufficiently elevated to melt the paste, and convert it into glass, but 
not high enough to fuse the substance of the pottery, which I find 
is fusible at a very high temperature. It may also, I think, be 
inferred, that the ferruginous colouring matter was mechanically 
mixed with the paste, before being applied ; — an inference I am led 
to, from the circumstance, that where the varnish is very thin, it is 
no longer opaque, — the red colour of the clay is seen through it ; 
and, on minute inspection, with a magnifying glass, evidently owing 
to a partial absence of the black colouring matter. 
Probably the ancient vases, of superior quality, in which the red 
colour of the clay is so finely contrasted with the shining black of 
the varnish, were subjected to heat, in close vessels, as the Turkish 
pipe-bowls, which are of similar material, and of the same pure red 
colour, are baked at present : they are placed in a dome made of 
clay, from which the air is excluded, the fire being heaped up 
around. 
VOL. iv. x * 
