Dictionarium polygraphicum. Articles added by way of supplement. To discover gold under a black colour, with an ivory Point, a great secret and very beautiful.

Dictionarium Polygraphicum:
Or, The Whole Body of Arts Regularly Digested.
Vol II.
London: Printed for C. Hitch and C. Davis in Pater-noster Row, and S. Austen in St. Paul's Church Yard. MDCCXXXV.
Having first laid your gold on your work, and burnish'd it well, grind lamp-black with linseed-oil, or nut-oil, adding to it as much umber, and black to make it dry, and then as much oil of spike, as linseed-oil.

Lay the black upon the gold, very smooth and even, and let it stand to dry about a day, more cr less, according to the time; it is dry enough when it will not stick to your fingers. Then take a point of ivory or stag's-horn well sharpened, rub it upon a piece of glass to take off the roughness, that it may no: scratch the gold or the white; then draw what you please with the point, discovering the gold.

If it appear bright and shining, and the black be not uneven and slovenly about the edges of the strokes you have made, then is your black in good temper; but if in discovering the gold, it seem tarnish'd, the black is not dry enough, therefore let it stand to be a little drier.

If the black be troublesome to get off, and cannot be easily done with an unslit pen, then mix spike oil, till it come to work easily, clean and bright; and then you may easily draw the finest hair-strokes.

The black being thus ordered, cover the burnished gold all over, with a soft pencil; and then with the feather of a turky-cock's tail, pass'd over the black as even and smooth as you can, free from all manner of dust or filth; being dry and having made your draught or figure as large as the work, follow the track of the lines with the point, and discover and lay open the gold.

If you would have the figures of birds, or little beasts, or any thing else, find out the strong lights of them, discover them by hatching with a pen or the point of a pen, is not too sharp; but if by the strokes approaching too near one another, you should happen to make a fault, you may mend it by laying on a little black, letting it dry.

If the way of making great lights be not easy, or shadows are more easy and pleasing to you, you may discover the gold with a point of soft wood, that it may not scratch the gold, which you must discover or lay open to the bigness of your whole figure, shadowing the proper places, as the nose, eyes, hair, &c. leaving it to dry; then hatch it with a point according to the judgment of him who draws it.

That you may know when 'tis dry enough to hatch, always at the same time you cover your work, cover also a little waste piece for trials, to prevent the spoiling your work.

Your work being finished, let it stand three or four days to dry, and varnish it with drying varnish twice, if you find there is occasion.

When you lay on the black, do but one piece at a time, because otherwise, some of it being too dry, it will be difficult to discover the gold.

You must also be very curious in the first laying on the varnish, to spread it gently for sear of defacing the work.

To do the same after a more easy manner.

Having cover'd your work with burnish'd gold or silver, (which you please) mix and grind lamp-black and umber together very well with water, taking care not to put so much umber as to spoil the black; then add some of the yolk of an egg, grinding it with it, and lay it on your work with a soft pencil or brush very smooth, and when it is dry (if you see occasion) give it a second laying of the same black, and with an ivory point very smooth, discover your work. If the black does not come easily off, there was too little of the yolk; if the strokes be too broad and ragged, then there was too much yolk of egg.

This way of discovering the gold, is more shining than the other; but be sure to be careful in varnishing you do not pull off the black, nor cause it to sully; and to that end, be sure to work with a soft pencil, and smooth stroke.

You need not much fear, in laying on the varnish the second time, provided it be not too thick, and it be oil of spike varnish.

To do the same another way.

Having laid the black on the burnish'd gold, as before directed, mix equal parts of linseed-oil and oil of spike, which lay lightly on with a large pencil; let the work stand to dry for 4 or 5 days more or less, according as you find the gold more or less easy toappear bright and shining.

By this way you may allow almost what time you will, always remembring to make a tryal, before you go to work.

For blue take azure; for red, fine lake; for green, verdegrease; and so in all other colours, being mixt and ground with the yolk of an egg, as before directed.

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