Improvements in or relating to Lamps Applicable for Colour Matching or General Lighting Purposes.
Year: 1899

page_text: Date of Application, 24th Nov., 1899
Complete Specification Left, 24th Aug., 1900-Accepted, 1st Feb.,
1901
Date of Application, at IUV+)
Complete Specification Left, 24th Aug., 1900-Accepted, 1st Feb., 1901
PROVISIONAL SPECIFICATION.
Improvements in or relating to Lamps Applicable for Colour Matching
or General Lighting Purposes.
We, ARTHUR DUFTON, M.A., B.Sc., of 81, Watson Road, Sheffield, in the County
of York, Inspector of Science and Art Department, and WALTER MYERS GARDNER,
of The Technical College, Bradford, in the County of York, Director of the
Dyeing Department, do hereby declare the nature of this invention to be as
follows:-
All artificial lights at present known differ from daylight in character. Gas-
light is useless for colour work, and although the magnesium light and more
particularly the electric arc light are now extensively used for colour matching,
it is freely admitted by all practical men that they are unsatisfactory.
We find however that almost any artificial light can be made to resemble day-
light by absorption of such rays as are found present in excess in such artificial
light when compared with the spectrum of normal daylight. To bring about
this, the light is caused to pass through a suitable coloured screen or is reflected
at a coloured surface, or a combination of both may be employed.
For practical purposes the electric arc light is most convenient to apply, the
ordinary white or opalescent globe being in such case replaced by a coloured glass
globe so tinted as to absorb all rays of light in excess, and to render the emergent
light the same quality as daylight; or a separate coloured globe may be employed.
Another method is to reflect the entire light of the arc or other lamp against a
surface coloured to the required tint.
1000
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool,
Patent Agents for the Applicants.
Improvements in or relating to Lamps Applicable for Colour Matching
or General Lighting Purposes.
We, ARTHUR DUFTON, M.A., B.Sc., of S1, Watson Road, Sheffield, in the County
of York, Inspector of Science & Art Department, and WALTER MYERS GARDNER,
of The Technical College, Bradford, in the County of York, Director of the
Dyeing Department, do hereby declare the nature of this invention and in what
T
077

page_text: manner the same is to be performed, to be particularly described and ascertained
in and by the following statement: -
All artificial lights at present known differ from daylight in character. Gas-
light is useless for colour work, and although the magnesium light, and still
more the electric are light are now extensively employed for colour matching, it is
freely admitted by all practical men that they are unsatisfactory.
We find however that almost any artificial light can be made to accurately
resemble daylight by absorption of such rays as are found present in excess in
such artificial light when compared with the spectrum of normal daylight. To
bring this about, the light is caused to pass through a suitable coloured transparent
or translucent screen or is reflected from a suitably coloured surface, or a com-
bination of both these plans may be adopted.
All artificial illuminants differ essentially from daylight in being richer in rays
of low refrangibility. For the absorption of the excess of light of low
refrangibility we find the range of blue colours produced by cupric salts either in
solution or in the form of glass suits admirably.
In absorbing the excess of light of low refrangibility the light is caused to
pass through a screen coloured to the required tint of blue by means of cupric
salts. The screen may consist of a solution of a cupric salt or salts or preferably
consists of glass coloured by cupric oxide or other compound of copper. If
reflecting screen be used, the screen may be coloured by admixture with a cupric
salt.
a
For practical purposes we prefer the electric arc light as most convenient to
apply. In this case the ordinary white or opalescent globe may be conveniently
replaced by a globe tinted to such a depth of blue as to render the emergent
light practically the same quality as daylight; or a separate coloured globe may
be employed. In the case of enclosed arc lamps in which the arc is produced in a
partial vacuum, either the internal glass cylinder or the external globe or both
may be coloured to serve as the absorbing medium.
To correctly tint the screen to the required intensity and shade depends upon
the character of the illuminant. In the case of electric arc lamps the character
of the light emitted varies considerably with the strength of the current used and
also depends upon the purity of the carbons. Further, lamps of the enclosed arc
pattern produce a light richer in violet rays than lamps with an open arc. Conse-
quently it is impossible to give exact particulars of the required depth of blue
and therefore of the quantity of copper sulphate or other cupric salt that may be
required to tint a given area. The exact depth of blue can only be determined
experimentally for each lamp by careful comparison with good daylight from a
north sky.
In the case of some forms of electric arc or lights other than the electric arc.
the colour of the screen may require to be modified by the further addition of
other colouring substances. The rays required to be absorbed can be readily
determined by comparing the spectrum of the light with the spectrum of normal
daylight. An excess of light in any part of the spectrum is neutralized by an
addition to the screen of a substance capable of absorbing such light to the
required extent.
In making glass globes or cylinders or reflectors the addition of copper and other
bases is made to the glass itself or is flashed on the glass.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed, we declare that what
we claim is:-
1. The application to, or use in conjunction with, electric lamps or other
sources of artificial light, of coloured screens or reflectors, or a combination of
both, so selected as regards colour and tint as to absorb or intercept such coloured
rays as are found to be in excess of normal daylight, for the purpose of rendering

page_text: the light of the same quality as daylight, or suitable for matching or viewing
colours.
2. In the manufacture of coloured screens or reflectors for use with an artificial
source of light to render it of the same quality as daylight, or suitable for match-
ing or viewing colours, the use of copper in the form of a cupric salt, or as an
ingredient of the material when such consists of glass substantially as described.
Dated this 23rd day of August 1900.
WM. P. THOMPSON & Co.,
Patent Agents of Liverpool, Manchester, Birmingham & London.