Thus, if you take a piece of transparent Glass that is well colour'd, and by heating it, and then quenching it in Water, you flaw it all over, it will become opacous, and will exhibit the same colour with which the piece is ting'd, but fainter and whiter.
Or, if you take a Pipe of this transparent Glass, and in the flame of a Lamp melt it, and then blow it into very thin bubbles, then break those bubbles, and collect a good parcel of those laminæ together in a Paper, you shall find that a small thickness of those Plates will constitute an opacous body, and that you may see through the mass of Glass before it be thus laminated, above four times the thickness: And besides, they will now afford a colour by reflection as other opacous (as they are call'd) colours will, but much fainter and whiter than that of the Lump or Pipe out of which they were made.
Thus also, if you take Putty, and melt it with any transparent colour'd Glass, it will make it become an opacous colour'd lump, and to yield a paler and whiter colour than the lump by reflection.
The same thing may be done by a preparation of Antimony, as has been shewn by the Learned Physician, Dr. C.M. in his Excellent Observations and Notes on Nery's Art of Glass; and by this means all transparent colours become opacous, or ammels. And though by being ground they lose very much of their colour, growing much whiter by reason of the multitude of single reflections from their outward surface, as I shew'd afore, yet the fire that in the nealing or melting re-unites them, and so renews those spurious reflections, removes also those whitenings of the colour that proceed from them.
As for the other colours which Painters use, which are transparent, and us'd to varnish over all other paintings, 'tis well enough known that the laying on of them thinner or thicker, does very much dilute or deepen their colour.
Painters Colours therefore consisting most of them of solid particles, so small that they cannot be either re-united into thicker particles by any Art yet known, and consequently cannot be deepned; or divided into particles so small as the flaw'd particles that exhibit that colour, much less into smaller, and consequently cannot be diluted; It is necessary that they which are to imitate all kinds of colours, should have as many degrees of each colour as can be procur'd.
And to this purpose, both Limners and Painters have a very great variety both of Yellows and Blues, besides several other colour'd bodies that exhibit very compounded colours, such as Greens and Purples; and others that are compounded of several degrees of Yellow, or several degrees of Blue, sometimes unmixt, and sometimes compounded with several other colour'd bodies.
The Yellows, from the palest to the deepest Red or Scarlet, which has no intermixture of Blue, are pale and deep Masticut, Orpament, English Oker, brown Oker, Red Lead, and Vermilion, burnt English Oker, and burnt brown Oker, which last have a mixture of dark or dirty parts with them, &c.
