The diameter is given in the lead enclosed; it is beaten with a hammer and several times extended; the lead is folded and kept wrapped up in parchment so that the powder may not be spilt; then melt the lead, and the powder will be on the top of the melted lead, which must then be rubbed between two plates of steel till it is thoroughly pulverised; then wash it with aqua fortis, and the blackness of the iron will be dissolved leaving the powder clean.

Emery in large grains may be broken by putting it on a cloth many times doubled, and hit it sideways with the hammer, when it will break up; then mix it little by little and it can be founded with ease; but if you hold it on the anvil you will never break it, when it is large.

Any one who grinds smalt should do it on plates of tempered steel with a cone shaped grinder; then put it in aqua fortis, which melts away the steel that may have been worked up and mixed with the smalt, and which makes it black; it then remains purified and clean; and if you grind it on porphyry the porphyry will work up and mix with the smalt and spoil it, and aqua fortis will never remove it because it cannot dissolve the porphyry.

If you want a fine blue colour dissolve the smalt made with tartar, and then remove the salt.

Vitrified brass makes a fine red.

729.

STUCCO.

Place stucco over the prominence of the..... which may be composed
of Venus and Mercury, and lay it well over that prominence of the
thickness of the side of a knife, made with the ruler and cover this
with the bell of a still, and you will have again the moisture with
which you applied the paste.  The rest you may dry [Margin note:  On
stucco (729. 730).] [Footnote:  In this passage a few words have been
written in a sort of cipher—­that is to say backwards; as in l. 3
erenev for Venere, l. 4 oirucrem for Mercurio, l. 12 il
orreve co ecarob for il everro (?) co borace.  The meaning of the
word before "di giesso" in l. 1 is unknown; and the sense, in
which sagoma is used here and in other passages is obscure.—­
Venere and Mercurio may mean ‘marble’ and ‘lime’, of which
stucco is composed.

12.  The meaning of orreve is unknown.]

well; afterwards fire it, and beat it or burnish it with a good burnisher, and make it thick towards the side.

STUCCO.

Powder ... with borax and water to a paste, and make stucco of it, and then heat it so that it may dry, and then varnish it, with fire, so that it shines well.

730.

STUCCO FOR MOULDING.

Take of butter 6 parts, of wax 2 parts, and as much fine flour as when put with these 2 things melted, will make them as firm as wax or modelling clay.

GLUE.

Take mastic, distilled turpentine and white lead.

On bronze casting generally (731-740).