GLUE OR COMPOSITION STAMPS.
Stamps made from a mixture of glue, glycerine, and molasses or from
similar mixtures are an excellent substitute for india rubber stamps.
Properly made they possess all the flexibility that characterizes the
rubber ones, while for fatty inks such as that used by printers and
lithographers, which inks tend to destroy rubber stamps, they are much
better. They are adopted by the United States government for making
dating stamps for use in the Post Office Department; by publishers
of directories for printing advertisements on the edges of their
publications, and in many other cases. Our description shall follow as
closely as possible the process and methods used in the United States
Post Office. They are there termed “composition blotters.”
The composition of which they are made is printer’s roller material.
Nine and one-half pounds of fine quality glue are soaked in just enough
soft water to cover it until it is thoroughly softened. It is then
melted. In the Government Department a steam kettle is provided for
the purpose. An ordinary glue pot will answer for smaller quantities.
When melted four and one-half pounds of best molasses and seven pounds
of glycerine are added, and the whole is thoroughly mixed. The formula
varies a little according to the prevailing temperature, less molasses
being added when the weather is warm, and _vice versa_. Experience is
here the best teacher. When well mixed it is poured out into tin pails
whose inner walls or sides and bottom have been rubbed over with oil.
It solidifies in cooling and becomes a clear brown jelly quite free
from any stickiness or superficial moistness.
[Illustration: MODEL FOR COMPOSITION STAMP MOULD.]
In use it is turned out of the pails to which, owing to the oiling, it
does not adhere. It is cut off as wanted, melted by heat and cast in
oiled moulds.
The latter are made of type metal to which one-third its weight of lead
has been added. As model for the mould or matrix a brass model of the
stamp is employed. This represents a sort of oval based cut-off or
truncated cone, about an inch high and a little over an inch long on
its base. A flange extends outward from its base and a tube is provided
to fit this flange. Its smaller end corresponds to the face of the
stamp, and on it are engraved in full relief any permanent characters,
circles or border lines, etc. Through its centre one or more apertures
are made. Into these, changeable steel, iron or brass type may be
introduced and set fast with plaster of paris.
[Illustration: COMPOSITION STAMP MOULD.]
To make the mould, the brass model with its movable type set as
required is placed upon a flat table or plate, face upward, and
surrounded by the tube, as shown in partial section in the cut, page
114. The tube is a strip of sheet iron, which is bent around the flange
and is secured in place by a wire twisted around it. The melted alloy
(type, metal and lead) is poured into the space thus formed until
it rises a quarter of an inch above the face of the model. In a few
minutes it sets and is removed and allowed to cool. This gives a cup
with the inscription and design depressed or in _intaglio_ upon its
inside base. This is shown in the cut, page 115, partly in section; it
will of course be understood that the mould forms a complete cup.
To make the stamp the interior surface of the mould is oiled with a
stiff brush. It is not material what oil is used. The composition
melted by heat is then poured into the cup, and is allowed to solidify.
Owing to the conical shape of the mould it is readily removed. The
mould must be hot but not too much so.
In the Post Office stamps the date requires to be changed frequently.
Some of the figures do duty for two or three days each month. Thus the
figure 8 is in the designation of three days, the eighth, eighteenth,
and twenty-eighth. There are three changes involved therefore in
connection with this day numeral. When a stamp mould or matrix is
cast the place of numerals that are to be changed is filled with a
blank space in the part where the type would otherwise come. A number
is stamped in this space when needed, by means of an ordinary steel
number-punch.
When the number is to be changed the old character is scraped or cut
out, leaving a small irregular hollow. A very small piece of soft
lead, about one-sixteenth of an inch on each side, is dropped into
the hollow. With a flat faced punch it is flattened out, and on it the
new number is impressed by a steel punch. This operation is repeated a
great many times before the matrix is worn out.
[Illustration:
OPEN SHUT
COMPOSITION STAMP HANDLE.]
In the cut, page 115, one number is shown as stamped into the soft
lead, and at the other end of the stamp is a blank space ready for a
number.
The casting of a stamp is so extremely simple that no attempt is made
to use movable type, as in permanent rubber dating stamps.
While it is obvious that these composition stamps could be attached
directly to wooden handles, a special style of handle, shown in the
cuts, is employed by the Post Office. A wooden handle carries at
its end a brass base, to which is pivotted a swinging piece that is
perforated by a conical oval aperture a little larger than the small
end of the stamp. The edges of this aperture are slightly rounded.
It is swung around as shown in the first figure, and the stamp,
previously moistened on its sides, is forced in. If the stamp is
properly made it is surprising how much force may be used to insert
it. If the edges of the brass swinging piece are not rounded there is
danger of the composition being cut. The stamp in its brass frame is
then swung back over the brass base, where it is secured by a catch.
The stamp is now ready for use, as shown in the second figure of the
cut.
It is imperative that no aqueous or glycerine ink be employed for
continuous work with such stamps. Common printers’ ink is perfectly
satisfactory, and the work may be nearly or quite as good as that
executed by an india rubber stamp.
The Post Office manufactures a pad for use with printers’ ink into
whose manufacture the same composition enters. The ink retainer is a
piece of fine felt, one-quarter to one-half an inch thick. This is
placed in the bottom of a shallow steel mould, where it enters for half
its depth into a recess that it accurately fits. The composition from
old stamps, melted up, is then poured upon and around it, the mould
being previously oiled. When it is full a piece of strong manilla
paper, of the area of the felt only, is placed upon the bottom of the
glue pad on its centre, which as it lies in the mould is its uppermost
part. The paper adheres strongly as the glue hardens. Eventually it
is turned out of the mould, and a pad, shown in the cut, is produced.
The dotted lines show the limits of the felt pad. The glue composition
underlies, surrounds and extends outwards from the felt portion. It
is found that the elasticity of the composition makes the pad much
pleasanter for rapid stamping.
[Illustration: COMPOSITION INK PAD.]
The above description gives the clew to making any stamp of this
description. The matrix may be of dental plaster, or of oxychloride of
zinc cement. The mould may be built up of type of any kind.
The composition is so cheap that the stamp can be made quite thick.
This gives it a high degree of elasticity and adaptability to uneven
surfaces. It may be mounted by adherence upon a flat board or block,
provided, if necessary, with handles. If the board or block is
placed upon the composition while it is still warm and liquid, as it
solidifies the board and composition will adhere with great tenacity.
All moulds or surfaces to which it is desired that the melted
composition shall not adhere must be oiled.
The moulds must not be cold or the composition will not enter the fine
divisions. If on the other hand they are too hot the mixture will
adhere. Experience will teach the right conditions for success.
Below are given other formulæ for roller composition. The formula
already given in this chapter is that used by the United States Post
Office Department.
I. “Old Home Receipt:” Glue 2 lbs., soaked over night, to New Orleans
molasses 1 gallon. Not durable, but excellent while it lasts.
II. Glue 10½ lbs., molasses 2½ gal., Venice turpentine 2 oz., glycerine
12 oz.; mix as directed above.