Year: 1887

page_text: We, JOHANNES GAEDICKE of 74 Ritter-strasse of Berlin, Chemist, & ADOLF
MIETHE of the town of Potsdam in the German Empire, Chemist do hereby declare the
nature of our Invention and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement :-
Our invention relates to an improved magnesium light for photographic purposes
& has for its object the removal of those difficulties which have hitherto prevented
the general adoption of the same for photographic purposes, notwithstanding that
its eminent value as an artificial source of light is generally recognised in fact
experience proves that for momentary photographs or pictures produced in a fraction
of a second it is a valuable substitute for either the electric or day light, but for
several reasons these advantages could not be turned to practical account. This
may be explained by the fact that it has been the practice hitherto to burn the
magnesium in lamps, in the form of thin ribbon or wire, but it was found to be
exposure."
a most difficult matter to determine the proper
Another difficulty
arose in the burning of the wire itself as neither the method above mentioned of
burning the wire in lamps or of burning the same uncovered proved suitable for
employment in the Atelier for several reasons, amongst others, that the latte
portion of the wire was not consumed rapidly enough, that the wire was with
difficulty ignited, but more especially because the products of combustion were
afterwards to be disposed of. The action of the dazzling rays of the magnesium
"

page_text: light on the object was however a sufficient reason why the same was not employed
for photographic purposes. The various improvements invented for the purpose of
removing these difficulties have not attained the desired result. According to our
invention the magnesium is no longer used in the form of a thin ribbon or wire,
but as a fine powder which is mixed in a certain proportion with other bodies,
which readily give off oxygen (known to intensify the magnesium light) and also
simultaneously mixed or amalgamated with such bodies, as accelerate the combustion
of the mixture. Such substances or bodies are for example, chlorate of potash,
prussiate of potash, sulphurous and other combustion materials. Whereas prussiate
of potash exceedingly accelerates the combustion, the chlorate of potash, on account
of its containing a large amount of separable oxygen, performs the very essential
function of increasing the temperature to such an extent that the radiating light
& the action of the magnesium is greatly intensified. The combustion of the mixture
specified in the present specification lasts from about 3 to 6 of a second. It must
here be remarked that although the magnesium light, prepared according to our
invention, possesses several hundred thousand candle power, yet it is not possible for
the effect of a flash to be so powerfully felt that a reaction of the "model" could
take place.
This is explained by the fact that the time the flash takes to find its way from the
sensitive nerves to the central organ and from thence back to the operative nerves is
much longer than the limit given above for the burning of the powder and even if the
"model" should move, this movement could only have taken place, after the photo-
graph or picture was already taken or completed. Our said improved magnesium
powder or mixture is of great value for the purpose in question, because the burning
of the same, when ignited takes place without any explosion, whatever, expanding
gases not being objectionably produced. The rapidity of combustion depends con-
siderably upon the fineness of the magnesium powder & other ingredients & also upon
the degree of their mechanical intermixture. The most suitable mixture for this
purpose consists of:-

page_text: Having now particularly described & ascertained the nature of our said invention
& in what manner the same is to be performed we declare that what we claim and
desire to secure by Letters Patent is :-
1. The employment of a mixture of magnesium powder with oxygen yielding salts, as
for instance chlorate nitrate & other salts, as well as with substances that accelerate
the combustion such as prussiate of potash, amorphous phosphorus, sulphurous &
other combustive materials, pine soot etc., for instantaneous photography & for
producing a momentarily intense light, substantially as described in the foregoing
specification.
2. The employment of light coloring substances, or bodies in connection with the
herein described magnesium light in order to make the light more effective for the
corresponding colors, substantially as described in the foregoing specification.
PHILIP M. JUSTICE,
Associate Agent.