To Write Secret Letters
Put five cents' worth Citrate of Potassa in
an ounce vial of clear cold water. This forms an invisible fluid. Let
it dissolve and you can use on paper of any color. Use quill pen in
writing. When you wish the writing to become visible hold it to red hot
stove.
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Black Copying Ink Or Writing FluidPrevious:
Indelible Ink For Marking Linen
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