Secrets of Glass Manufactory - Compositions to Imitate Precious Stones, called French Paste

Secrets Concerning Colors and Painting
§ I.  Paint In Varnish On Wood
§ 2. Paint On Paper
§ 3. Compositions For Limners
§ 4. Make Transparent Color
§ 5. Compositions to Dye Leather
§ 6. Color or Varnish Copperplate Prints
§ 7. For Painting on Glass
§ 8. Color Preparation for Oil, Water, and Crayon
       Marble and Jasper Paper
       Methods to Clean Paintings
       Making Good Crayons
       Directions for Coloring Prints
       Directions for Painting in Oil
§ 9.  Preparation of Lapis Lazuli to Make Ultramarine

Making Invisible Ink

VII.  An invisible ink.

    1.  Dissolve one ounce of ammoniac salt in a glass tumbler of water, and write.  When you wish to make the writing appear, hold the paper to the fire, and it will become black.
    2.  The same may be done with the juice of an onion.

VIII.  Another way.

    Dissolve some alum and write with the liquor.  Steep the paper in water, and the writing will appear white.

XII.  To make an ink which appears and disappears alternately.

Write with an infusion of gall-nuts filtered through brown paper, and the writing will not be visible.  When you want to make it appear, steep a little sponge, or bit of cotton, into an infusion of vitriol, and pass it over the written place of the paper; the writing will immediately appear.  To rub it off, and make the paper look all white again, do the same with the spirit of vitriol, and all the writing will be gone.  To make it visible again, rub the paper over with oil of tartar; and thus continue forever.

XIII.  The invisible method of conveying secrets.

    1st Ink.   -    Infuse for twenty-four hours, half an ounce of gold litharge in half a pint of distilled white wine vinegar. and shake the bottle often during the first twelve hours of the infusion.  When all is well settled, decant the clear part into another phial, which you must stop carefully, and throw the faeces away.
    If you have any secret to communicate to a friend, write it with this liquor, and it will be no more visible than if you wrote it with clear pump water.

XIV.  An ink to write over the other.
    2nd Ink.   -    Over the secret, written with the first invisible ink, you write any indifferent matter with the following composition.
     Burn some corks in the fire; and when that are so thoroughly burnt as to blaze no more, put them into a basin, and soak them with brandy; then grind them into a paste, which when you want to use, you dilute with distilled water, till it is fit to write with like any other ink.

XV.  Another ink which effaces the second, and makes first appear.

    3rd Ink.   -    Dilute rose water and sorrel juice separately.  Put half a pint of each together in a bottle, with two ounces of quick lime, and one of auripigment.  Stir this well, now and then, and let it infuse during twenty-four hours, as you did the first.  Decant the clear part, and throw the grounds away.
    When you want to find out what was written with the first invisible ink, and which lies concealed under the second black one, steep a sponge into this present liquor, and passing quickly over every line; what was written in black vanishes at one stroke, and what was invisible appears in its stead as black, and as much effaceable as it written with common ink.

XXVIII.  A way of writing which will not be visible, unless you hold the paper to the sun, or the light of a candle.

    Take flake white, or any other whitening, and dilute it in a water impregnated with gum adragant. If you write with this liquor, the writing will not be perceivable, unless you apply the paper to the sun, or the light of a candle.  The reason why it is so, is, that the rays of light will not find the same facility to pass through the letters formed with this liquor, as through the other parts of the paper.

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