CHAP. XXI. Another Extraordinary Way of making Ferretto of Spain, which is a great Secret.
THis way of making Ferretto is not common, nor much known; wherefore we will here teach it for Satisfaction of the Curious. It is of a very wonderful use, not only for Tinging Glass, but for several Chymical Operations, wherein we know the use of it, which is very surprizing, if a second and further Preparation be made of it, whereof we shall here make no mention, it being foreign to our Subject; but take that which serves for Tinging Glass as follows.
Take very fine Steel, for in the Perfection of that consists all the Excellency of the Work; make it in∣to thin Plates, or file it: also do the same▪ with Cop∣per or Brass, viz. make that also into thin Plates, or take the Filings of it, one part to two of the Steel; put them into a Crucible stratum super stratum, lute them, and put it on a gentle Fire for Eight Hours, then take it out, and melt the whole in a Wind-Furnace, then cast it in a Lingot, or in lit∣tle Plates, and the business is done.
To make use of this in Glass, you must calcine these Plates, then pound them, and searce them, and keep that Powder in a Pot close shut up for use.