But it is rubbed before being put into use. Some regard it as a compound of red lead (isrinj). Isrinj is also called sankh. It is the lime of
lead. The lead is burnt and roasted with sulphur till it attains a red
colour. Marwah and isrinj are then leached out with water, giving the
impression as if nothing remains.
There is another kind of mina. Here an equivalent weight of bruised
crystal is mixed with marwah. Instead of isrinj, tin is calcined in two
thirds of its weight and its lime is poured, followed by natron which is
added one-fourth by weight. The compound then becomes lighter. Isrinj
generates ponderousness in it, just as between lead and tin there is a proportion of lightness and gravity. We shall describe both these in our
Second Discourse. The glassiness in mina is obtained through gravel, just
as in glass and natron glassiness is obtained through sand. Buraq and
tankar which are homogeneous things help in its quick melting.
From the borax which accumulates upon the crucibles is acquired
the green glass. Some regard it as the real glass as it accepts all kinds of
colours and it congeals in objects with which it is blown or in the kilns of
glass-makers. Its weight, with the axis of the ghubari (ruby) as the standard, is 99-1/3.
Some people use it in place of isrinj and the lead since this too
comes out of the calcined lead, but this is poorer than red lead. As far as
colour is concerned, they determine the yellow colour through red lead
or the dross of the lead and also mention za'fran-i-hadid (yellow iron) in
this context. Z'afran-i-hadid means rust. Greenness is associated with
copper, whether copper is burnt to give rusakhtaj (antimony) or is associated with dust or rust. Redness follows from calcined copper, blackness
from iron dust, opacity from magnesia and white colour from ceruse
which is calcined lead. The ruby-like colour is associated with calcined
gold and the violet colour with lapis lazuli and agate. It should, besides,
be noted that transparency is found in yellow and green colours and is
removed by red, white and black colours.
There are different ways in which it is prepared and coloured. There
are various statements upon these techniques, but the authority of these
techniques cannot be believed until and unless the work of these experts
has been personally seen and, in fact, these techniques have been repeated with respect to glass and mina. Cups are made in the same way
too, and the chemicals and techniques employed in their preparation and
dyeing are the same as described earlier.
In China different kinds of earth are added to, and mixed with the
flint-stone which we have already described under mina. This earth is