Engravers and Statuaries may so harden their Tools, that they may hold their points long, if they be to cut stones.
That Iron may be hardened by Cementation with Salts, so that it may serve instead of Steel, is now openly known; but the iron or steel is to be kept in cementation as long as need shall be, not with common salt alone, but mixed with the powder of coals and salt of ashes; then the Iron grows as hard as steel, but steel is rendered harder than it was before.
Point IV.
Embroiderers may put any durable Colour they please upon the Silk with which they work.
It may be known, that Nitre, as being a depurated salt, will easily induce colours, and constantly preserve them, yea, exalt them, which many know, they especially who dye cloth with rich grain colours, as Scarlet, Crimson, &c. when they add the spirit of Nitre in the boiling, to aluminate it, (as the Dyers call it) the colour is wonderfully exalted, and made much more fiery, so that it may be sold dearer than common Crimson or Scarlet. This spirit of Nitre also tingeth Ashes, Nails, or Hoofs, Quills, or Feathers, with a golden colour, but if the Nitre be fixed by calcination, then it also equally exalteth, but not into a red, but a Purple; Dyers use Potters ashes for these Works, but fixed Niter is much purer, and rendereth the Work more beautiful than those impure ashes.
Point V.
They who Paint Glass, by an easie Work, may thence prepare all Colours or Enamels for Glass, so that there will be no need to have them from Venice.
The Painters of Glass sometimes complain, that their fusory Glass or Enamel will not readily flow, and that the Glass which they are to colour is melted first; the Salt of the Earth being fixed, remedieth this, if the colouring Glass be mixed with it in a due proportion, and again melted, for by this means they will be rendered fluxible at pleasure.
Point VI.
They who work in Wax, by the benefit of this, may whiten it exceedingly; and colour it as they please.