Improvements in Envelopes to Detect and Prevent Opening same Fraudulently.
Year: 1889

page_text: Date of Application, 3rd Oct., 1889
Complete Specification Left, 2nd July, 1890-Accepted, 13th Sept., 1890
PROVISIONAL SPECIFICATION.
Improvements in Envelopes to Detect and Prevent Opening same
Fraudulently.
1, GEORGE CRUIKSHANK PULFORD, of 77 Cannon Street, City of London, Manu-
facturer of Magnetic Paints, do hereby declare the nature of this invention to be as
follows:-
The object of this invention is an envelope which may be of the ordinary con-
struction but provided with indications, designs, or devices visible only when the
envelope has been tampered with or an attempt has been made to open it when sealed
up, so that any such attempt would be detected. The gum flap of my envelope is
protected from being opened by steaming, or moistening, as may be done with
ordinary unprotected envelopes.
For the purpose of my invention I print, mark, or otherwise form invisible indi-
cations, designs, or devices upon the outside or the inside of the flap portion of an
envelope in such a manner that if moisture or steam be applied for the purpose of
wetting the gum, or cement, the indications or devices will become permanently
visible by the action of such moisture upon the ink or fluid employed:
In order to protect the gum or cement becoming moistened by the application of
steam or liquid, I first coat the underside of the flap with a waterproof solution upon
which the gum or cement is afterwards applied in the usual manner, the waterproof
solution preventing the damp from passing through the paper of the flap and reaching
the gum on the other side
Dated this 3rd day of October 1889
H. GARDNER,
166, Fleet Street, London, Agent for the said G. C. Pulford.
COMPLETE SPECIFICATION.
Improvements in Envelopes to Detect and Prevent Opening same
Fraudulently.
I, GEORGE CRUIKSHANK PULFORD of 77 Cannon Street City of London Manu-
facturer of Magnetic Paints do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and ascertained
in and by the following statement :-
The object of this invention is an envelope which may be of the ordinary con-
struction but provided with indications designs or devises which become visible or
darken or change in colour when the envelope has been tampered with or an attempt
has been made to open it when sealed up, so that any such attempt would be detected-
The gum flap of any envelope is protected from being opened by steaming or moisten-
ing, as may be done with ordinary unprotected envelopes.
For the purpose of my invention 1 print mark or otherwise form invisible or other
indications, designs or devises upon the outside or inside of the flap portion of the
envelope in such a manner that if moisture or steam be applied for the purpose of
wetting the gum, or cement the indications will become permanently visible or change
in colour by the action of such moisture upon the ink or fluid employed.
The mixture I prefer to einploy is-One part by weight of uranium acetate, one
part of ferrocyanide of potassium-three parts of white lead or white zinc or a
mixture of these; to which I add lithographic vanish and turpentine in sufficient
quantity to produce an ink or composition of the desired consistancy.
A design or impression made upon the envelope flap with this composition will be

page_text: of a pale (white or yellow) tint, and when water or steam is applied the design
becomes permanently, a dark brown colour.
Having now particularly described and ascertained the nature of the said
invention, and in what manner the same is to be performed, I declare that what I
claim is
The application to envelopes of designs, marks &c. which become visible or change
or darken in colour when moistened, steamed or tampered with substantially as and
for the purpose herein described.
GEORGE C. PULFORD.