Dictionarium polygraphicum. Proper rules and matter for all sorts of Enamel, with directions for qualifying the fire, in order to succeed well.

Dictionarium Polygraphicum:
Or, The Whole Body of Arts Regularly Digested.
Vol I.
London: Printed for C. Hitch and C. Davis in Pater-noster Row, and S. Austen in St. Paul's Church Yard. MDCCXXXV.
1735
This most agreeable way of enriching gold by Enamel, which proceeds from the beautiful variety of colours which may be apply'd, being an art no less painful than necessary for ornament, we proceed to lay down such methods in this book, as shall equally answer the benefits of the publick, and satisfaction of the more curious.

We propose in the first place, to give direction for the choice of matter to be us'd, and thence shew the preparations for all sorts, and how to make and suit the colours most convenient on Enamel.

The method not only used by the goldsmiths, but by such as form portraitures with it of all sorts, as men, beasts, fowl, and other curiosities, very naturally, by a just disposure of the colours, is most admirable; to effect which no more is requir’d than a lighted taper, and a hollow pipe of metal for that purpose, to blow the blaze to the matter, and make it malleable and soft, and thence the several figures are drawn or impress'd thereon.

And this may be so far improv’d and heightned, as to admit of performances rather to be thought the essay of a divine than human artist. Witness that notable piece of a chariot drawn by two oxen, of which Cardan takes notice in the fifty second chapter of his tenth book, which was so compleatly done in miniature, that the whole might be cover'd with the wing of a fly. The ship rigg'd, and man arm’d, which Howel says he saw. Those little statues of men, with several other curiosities of figure Vornicus also assures us of. Not to omit the church of st. Mark at Venice, where the Mosaic-work is plentifully interlaced with history of all sorts, distinguishable by the variety of colours, and gildings, and all consisting of several different subjects. In short, what account Agricola has left us of these matters, in his twelfth book, give us no less cause to admire this art than he had, when he saw such notable pieces of which he makes mention, and which he assures us was deservedly very great. The use of Enamel is very ancient, however that of working on metal is more modern; and for the great perfection to which it is arriv'd, we are oblig'd to this present age.