ROMAN POTTERY FOUND IN BRITAIN. 
3 
the shades of enamel glaze produced during the I. — IV. centuries 
were moss-green, olive-green, grass-green, yellowish-green, citron- 
yellow, greyish-brown, red, copper-red, and black. Schumacher, 
Altevtumev u. h. Vovzeit , p. 295, plate 52. 
In describing the red glaced crockery found in this castellum, 
Drexel ( Faimingen , p. 80) says : “ The expression ‘glazed ’ replaces 
the technically false one of ‘ varnished ’ hitherto mostly employed 
for this kind of ware.” 
The methods of glazing and colour-coating have been dealt 
with in the preceding section, of which the following is a revised 
summary :— 
1. Enamel glazing .—The vessel in biscuit state (after first firing) 
is painted or coated with a frit, consisting of finely powdered 
vitrified clay, mixed in water with a powdered metallic oxide for 
colouring. It is then re-fired at a temperature only sufficient to 
vitrify the glaze. 
2. Red terra sigillata glaze. —The vessel in biscuit state is dipped 
in a watery slip of the same kind of clay strongly coloured with 
red iron oxide and probably containing some kind of alkali. It 
is then re-fired at a sharp heat. 
3. Belgic black or terra nigra glaze. —The biscuit ware is steeped in 
a thin solution of well levigated clay, and after drying and polishing 
(a) coated with powdered iron pyrites or steeped in a solution of 
green vitriol (copperas), and fired with bituminous fuel (Kimmer- 
idge shale, pitch, &c.) ; * (6) coated with ruddle and fumed ; or (r) 
coated with silicate of iron (ground iron, “ bull dog,” iron scale) 
and re-fired in the ordinary way. 
4. Hcematite facing. — (Prehistoric Egyptian or black topped 
ware). The leather hard or air dried vessel is polished, coated 
with haematite (ruddle) and baked upside down in an open wood 
fire,—the black top is the portion covered by ashes. 
5. Matt black colour coating. —The biscuit ware is dipped in a clay 
slip containing “ ground iron ” and fired in the usual manner ; or 
dipped in slip containing ruddle, and fumed. 
6. Slip coating. —The air dried vesssel is steeped in a slip (or 
engobe) of the same kind of clay, or clay of another colour, and 
fired in the usual manner. 
* The discovery of black ferrous sulphide in the pre-historic terra nigra 
glaze is due to Mr. George Bowman, F.C.S., &c. 
