According to Tarry, it is necessary to have recourse to alcohol to
discover whether the paper has been scratched in any of the parts and
then covered with a resinous matter to prevent the ink from blotting.

Place the document on a sheet of white paper and with a paint brush
dipped in alcohol of specific gravity 0.86 or 0.87 cover the place
supposed to have been tampered with. It may be discovered if the
writing thickens and runs when the alcohol has dissolved the resin.

Hold the paper moistened with alcohol between the eye and the light;
the thinning of the paper shows the work of the forger.

Some more skillful forgers use paste and resin at the same time to
mask their fraudulent operations; in this case luke-warm water should
be first employed and then alcohol; water to dilute the paste, and
alcohol to dissolve the resin. The result is that the ink added on the
places scratched out spreads, and the forgery is easily seen.

Test-papers (litmus, mauve, and Georgina paper) serve to determine
whether a paper has been washed either by the help of chemical agents,
acids incompletely removed, or the surplus of which has been saturated
by an alkali, or by the help of alkaline substances. The change of the
color to red indicates an acid substance; an alkali would turn the
reddened litmus paper to blue, and the mauve and Georgina test-papers
to green.

Take a sheet of test-paper of the same dimensions as the document to
be examined, moisten it, and cover it underneath with a sheet of
Swedish filter-paper. These two sheets together (the filter-paper
underneath) are then applied to the document which has been moistened