Transcriber Note
Text emphasis denoted as _Italics_ and =Bold=. Whole and fractional parts
of numbers as 123-4/5 and some fractions as 1/50th.
A MANUAL
OF
PHOTOGRAPHIC CHEMISTRY.
A MANUAL
OF
PHOTOGRAPHIC CHEMISTRY,
INCLUDING THE
PRACTICE OF THE COLLODION PROCESS.
By
T. FREDERICK HARDWICH,
LECTURER ON PHOTOGRAPHY IN KING'S COLLEGE, LONDON;
LATE DEMONSTRATOR OF CHEMISTRY IN KING'S COLLEGE.
Fourth Edition.
[Illustration]
LONDON:
JOHN CHURCHILL, NEW BURLINGTON STREET.
MDCCCLVII.
[_The Author reserves to himself the right of translating this Edition._]
PRINTED BY JOHN EDWARD TAYLOR, LITTLE QUEEN STREET, LINCOLN'S INN FIELDS.
PREFACE TO THE THIRD EDITION.
[Illustration]
It is a source of much, gratification to the Author to find himself called
upon to prepare a Third Edition of his Manual in less than fourteen months
from the date of its first publication. No greater proof could have been
afforded of the rapid advance which the Photographic Art is now making in
this country.
On once more entering upon the task of revision, the Writer has been led
to reflect in what way the utility of the Work may be promoted; and from
numerous inquiries he believes that this result will best be attained
by carefully omitting everything which does not possess _practical_ as
well as scientific interest. The majority of Photographers look to the
Art to furnish them with amusement as well as instruction, and they are
deterred from entering upon a study which seems to involve a great amount
of technical detail: these remarks however are not intended to discourage
a habit of perseverance and careful observation, but simply to distinguish
between the essential and the non-essential in the theory of the subject.
The present Edition differs in many important particulars from those which
have preceded it. It has undergone a fresh arrangement throughout. In some
parts it is condensed, in others enlarged. The Chapters on Photographic
Printing are entirely re-written, and include the whole of the Author's
investigations, as published in the Society's Journal. The minute
directions given in this part of the Work will show how much success
in Photography is thought to depend upon a careful attention to minor
particulars.
Another point which has been kept in view, is to recommend, as far as
possible, the employment of chemical agents which are used in medicine
and vended by all druggists throughout the united kingdom. It is often
an advantage to the Amateur to be able to purchase his materials near at
hand; and, if the common impurities of the commercial articles are pointed
out, and directions given for their removal, the 'London Pharmacopœia'
will be found to include almost all the chemicals necessary for the
practice of the Art.
Great additions have been made to the Index of the present Edition, which
is now so complete that a reference to it will at once point out the most
important facts relating to each subject, and the different parts of the
Work at which they are described.
In conclusion, a hope is expressed that this 'Manual of Photographic
Chemistry' may be found to be a complete and trustworthy guide on every
point connected with the theory and practice of the Collodion process.
_London, June 2nd, 1856._
PREFACE TO THE FOURTH EDITION.
[Illustration]
The Author has endeavoured to keep pace with the improvements which are
daily being introduced in the science and art of Photography. In the
present Edition alterations have been made in the style and general
arrangement of the work, and additional matter has been inserted.
Since the publication of the Third Edition, a series of experiments have
been made on the manufacture of Collodion, the results of which have
thrown further light upon the conditions affecting the sensitiveness of
the excited film, and have enabled the writer to introduce an organic
substance, "Glycyrrhizine," which will be found of service in making
Photographic copies of Engravings and similar works of Art.
Dr. Norris, of Birmingham, has within the last few months communicated a
paper on _dry Collodion_, which places the theory of that subject upon a
better footing than before. The Oxymel preservative process is now also
thoroughly understood, and may be considered certain.
In addition to the above, the "Albuminized Collodion" of M. Taupenot,
which experience proves to be one of the best dry processes at present
known, is included in this Edition.
_King's College, London, April 6th, 1857._
ERRATA.
Page 24, line 5, _for_ conditions _read_ condition.
Page 115, line 32, _for_ Iodide _read_ Iodine.
Page 194, line 15, _for_ p. 88 _read_ p. 188.
[_Transcriber Note--Corrections have been applied_]
CONTENTS.
PART I.
THE SCIENCE OF PHOTOGRAPHY.
Page
Introduction 1
CHAPTER I.
Historical Sketch of Photography 6
CHAPTER II.
THE SALTS OF SILVER EMPLOYED IN PHOTOGRAPHY.
Section I.--_The Chemistry of the Salts of Silver._--The preparation
and properties of the Nitrate of Silver--of the Chloride, Bromide,
and Iodide of Silver.--The Chemistry of the Oxides of Silver 12
Section II.--_The Photographic Properties of the Salts of
Silver._--The action of Light upon Nitrate of Silver--upon
Chloride, Bromide, and Iodide of Silver.--The blackening of
Chloride of Silver explained.--Simple experiments with sensitive
Photographic Paper 18
CHAPTER III.
ON THE DEVELOPMENT OF AN INVISIBLE IMAGE.
Simple experiments illustrating the process 25
Section I.--_Chemistry of the Substances, employed as
Developers._--Development shown to be a process of reduction.--The
chemistry of the principal reducing agents, Gallic Acid,
Pyrogallic Acid, and the Protosalts of Iron 26
Section II.--_The Reduction of Salts of Silver by Developing
Agents._--Reduction of Oxide of Silver--of Nitrate and Acetate
of Silver.--Varied appearance of Metallic Silver when finely
divided.--The reduction of the Iodide and other Salts of Silver
containing no Oxygen 30
Section III.--_Hypothesis on the Formation and Development of
the Latent Image._--Explanation of the terms under- and
over-exposure.--Diagram of Molecular change.--Moser's experiments
on development.--Curious perversions of development 34
CHAPTER IV.
ON "FIXING" the PHOTOGRAPHIC IMAGE.
Chemistry of the various substances which may be employed as
Fixing Agents.--Ammonia, Alkaline Chlorides, Bromides, and
Iodides.--Hyposulphite of Soda.--Cyanide of Potassium 41
CHAPTER V.
ON THE NATURE AND PROPERTIES OF LIGHT.
Section I.--_The compound Nature of Light._--Its decomposition into
elementary coloured rays.--Division of these rays into Luminous,
Heat-producing, and Chemical Rays 46
Section II.--_The Refraction of Light._--Phenomena of simple
refraction by parallel and inclined surfaces.--Refraction from
curved surfaces.--The various forms of Lenses.--The Foci of
Lenses.--Formation of a Luminous Image by a Lens 49
Section III.--_The Photographic Camera._--Its simplest form.--The
field of the Camera.--Chromatic aberration.--Spherical
aberration.--The use of Stops.--The double, or Portrait
combination of Lenses.--Variation between the Visual and Chemical
Foci in Lenses 54
Section IV.--_The Photographic Action of Coloured Light._--Diagram
of Chemical Spectrum.--Illustrative experiments.--Superior
sensibility of Bromide of Silver to coloured light.--Mode in which
dark-coloured objects are Photographed 60
Section V.--_On Binocular Vision and the Stereoscope._--Phenomena
of Binocular Vision.--Theory of the Stereoscope.--Wheatstone's
reflecting Stereoscope.--Brewster's Stereoscope.--Rules for taking
Stereoscopic pictures 66
CHAPTER VI.
THE PHOTOGRAPHIC PROPERTIES OF IODIDE OF SILVER UPON COLLODION.
Section I.--_Collodion._--Pyroxyline--its varieties--its chemical
composition.--Means of obtaining Nitro-Sulphuric Acid of the
proper strength.--Solvents for Pyroxyline.--Variation of physical
properties in different samples of Collodion.--The changes which
Iodized Collodion undergoes by keeping 75
Section II.--_The Chemistry of the Nitrate Bath._--Its solvent action
on Iodide of Silver.--Acidity and Alkalinity of the Nitrate
Bath.--Formation of Acetate of Silver in the Bath.--The substances
which decompose the Bath.--Changes in the Nitrate Bath by use 86
Section III.--_The Conditions which influence the Formation and
Development of the Latent Image._--Causes which increase or
diminish the sensitiveness of the film to Light.--Conditions which
hasten or retard development 91
Section IV.--_On certain irregularities in the Developing
Process._--Effect of particular states of the Bath, and of the
Collodion, in producing clouding of the Image, and of acids in
obviating it 103
CHAPTER VII.
ON POSITIVE AND NEGATIVE COLLODION PHOTOGRAPHS.
Definition of the terms Positive and Negative.--The same Photograph
often capable of representing both varieties 106
Section I.--_On Collodion Positives._--The Collodion and Nitrate
Bath best suited for Positives.--Peculiarities of Pyrogallic
Acid, and the Protosalts of Iron employed to develope Collodion
Positives.--The colour of Positives affected by the length of
exposure to light.--A Process for whitening Glass Positives by
means of Bichloride of Mercury 108
Section II.--_On Collodion Negatives._--The Collodion and Nitrate
Bath best adapted for Negatives.--Use of Glycyrrhizine to increase
the intensity.--Developing solutions for Negatives.--Conversion of
finished Positives into Negatives 113
CHAPTER VIII.
ON THE THEORY OF POSITIVE PRINTING.
Section I.--_The Preparation of the Sensitive Paper._--Its darkening
by light.--The conditions which affect its sensitiveness and the
vigour of the Image.--The colour of the print influenced by the
preparation of the paper 121
Section II.--_The Processes for Fixing and Toning the
Proof._--Conditions of a proper fixing.--The Salts of Gold used
as toning agents.--The properties of the single fixing and toning
Bath, with the conditions which affect its action 128
Section III.--_The Author's Photographic Researches._--The chemical
composition of the Photographic Image.--The various agencies
destructive to Photographs.--The action of damp air upon Positive
Prints.--The change in properties of the fixing Bath by constant
use 140
Section IV.--_The Fading of Photographic Prints._--The causes which
produce it.--The comparative permanency of Prints.--The mode of
testing permanency 160
CHAPTER IX.
ON THE DAGUERREOTYPE AND TALBOTYPE PROCESSES.
Section I.--_The Daguerreotype._--The nature of the sensitive
film.--Development of the Latent Image.--The strengthening of the
Image by means of Hyposulphite of Gold 171
Section II.--_The Processes of Talbot, etc._--The Calotype.--The
Waxed Paper Process of Le Grey.--The Albumen Negative
Process.--Taupenot's Collodio-Albumen Process 176
PART II.
PRACTICAL DETAILS OF THE COLLODION PROCESS.
CHAPTER I.
PREPARATION OF COLLODION.
Mode of preparing soluble Pyroxyline by the mixed Acids--by the Nitre
process.--Purification of the Ether and Alcohol.--Preparation of
the iodizing compounds in a state of purity 185
CHAPTER II.
FORMULÆ FOR SOLUTIONS REQUIRED FOR COLLODION PHOTOGRAPHS.
Section I.--_Formulæ for direct Positive Solutions._--The
Collodion.--The Nitrate Bath.--Developing fluids.--Fixing
liquids.--Whitening solution 201
Section II.--_Formula for Negative Solutions._--The Collodion.--The
Nitrate Bath.--Developing fluid.--Fixing liquid 208
CHAPTER III.
MANIPULATIONS OF THE COLLODION PROCESS.
Section I.--_Manipulations with moist
Collodion._--Cleaning the Plates.--Coating with
Collodion.--Exciting.--Exposing.--Developing. --Fixing 213
Section II.--_Simple directions for the use of Photographic
Lenses._--Portrait Lenses.--View Lenses.--Mode of finding the
chemical Focus 227
Section III.--_On copying Engravings, Etchings, Diagrams, etc._--Mode
of intensifying the Collodion 231
Section IV.--_Rules for taking Stereoscopic Photographs._--Mr.
Latimer Clark's arrangement for working with a single Camera 232
Section V.--_The Photographic delineation of Microscopic
Objects.-_-Arrangement of the apparatus.--Mode of finding the
chemical Focus.--Use of artificial light 235
CHAPTER IV.
THE DETAILS OF PHOTOGRAPHIC PRINTING.
Section I.--_Positive Printing by the ordinary process._--Selection
of the paper.--Preparation of Albuminized paper--of plain
paper--of Ammonio-Nitrate Paper.--Preparation of the fixing and
toning Bath.--Manipulatory details of Photographic Printing.--Mode
of washing and mounting the Proofs 240
Section II.--_Positive Printing by Development._--A process on
Chloride and Citrate of Silver.--On Iodide of Silver.--On Bromide
of Silver 259
Section III.--_The Sel d'Or Process for toning
Positives._--Preparation of the toning Bath.--Manipulatory details
267
Section IV.--_On Printing enlarged Positives, Transparencies, etc.,
upon Collodion_ 272
CHAPTER V.
CLASSIFICATION OF CAUSES OF FAILURE IN THE COLLODION PROCESS.
Section I.--_Imperfections in Negative and Positive Collodion
Photographs._--Fogging.--Transparent and opaque spots.--Markings
of all kinds--under- and over-exposure, etc. 276
Section II.--_Imperfections in Paper Positives_ 285
CHAPTER VI.
LANDSCAPE PHOTOGRAPHY BY THE COLLODION PRESERVATIVE AND COLLODIO-ALBUMEN
PROCESSES.
The Honey Keeping Process.--The Oxymel Process.--Photography on dry
Collodion.--Taupenot's Collodio-Albumen Process 288
PART III.
OUTLINES OF GENERAL CHEMISTRY.
CHAPTER I.
THE CHEMICAL ELEMENTS AND THEIR COMBINATIONS.
The more important Elementary Bodies, with their Symbols and
Atomic Weights.--The Compounds formed by their union.--The
class of Salts.--Illustrations of the nature of Chemical
Affinity.--Chemical Nomenclature.--Symbolic Notation.--The Laws of
Combination.--The Atomic Theory.--The Chemistry of Organic Bodies
305
CHAPTER II.
Vocabulary of Photographic Chemicals 327
APPENDIX.
Quantitative testing of Nitrate Baths.--Recovery of Silver from
waste solutions.--Reduction of Chloride of Silver.--Mode of
taking the Specific Gravity of liquids.--On Filtration.--The use
of Test-papers.--The removal of Silver stains from the hands,
etc.--Dr. Ure's tables of the strength of Sulphuric and Nitric
Acid of different densities.--Table of Weights and Measures 371
A MANUAL
OF
PHOTOGRAPHIC CHEMISTRY.
[Illustration]
INTRODUCTION.
In attempting to impart knowledge on any subject, it is not sufficient
that the writer should himself be acquainted with that which he professes
to teach. Even supposing such to be the case, yet much of the success
of his effort must depend upon the manner in which the information is
conveyed; for as, on the one hand, a system of extreme brevity always
fails of its object, so, on the other, a mere compilation of facts
imperfectly explained tends only to confuse the reader.
A middle course between these extremes is perhaps the best to adopt; that
is, to make selection of certain fundamental points, and to explain them
with some minuteness, leaving others of less importance to be dealt with
in a more summary manner, or to be altogether omitted.
But independently of observations of this kind, which apply to educational
instruction in general, it may be remarked, that there are sometimes
difficulties of a more formidable description to be overcome. For
instance, in treating of any science, such as that of Photography, which
may be said to be comparatively new and unexplored, there is great danger
of erroneously attributing effects to their wrong causes! Perhaps none but
he who has himself worked in the laboratory can estimate this point in its
proper light. In an experiment where the quantities of material acted upon
are infinitesimally small, and the chemical changes involved of a most
refined and subtle description, it is soon discovered that the slightest
variation in the usual conditions will suffice to alter the result.
Nevertheless Photography is truly _a science_, governed by fixed laws; and
hence, as our knowledge increases, we may fairly hope that uncertainty
will cease, and the same precision at length be attained as that with
which chemical operations are usually performed.
The intention of the author in writing this work, is to impart a thorough
knowledge of what may be termed the "First Principles of Photography,"
that the amateur may arm himself with a theoretical acquaintance with the
subject before proceeding to the practice of it. To assist this object,
care will be taken to avoid needless complexity in the formulæ, and all
ingredients will be omitted which are not proved to be of service.
The impurities of chemicals will be pointed out as far as possible, and
special directions given for their removal.
Amongst the variety of Photographic processes devised, those only will
be selected which are correct on theoretical grounds, and are found in
practice to succeed.
As the work is addressed to one supposed to be unacquainted both with
Chemistry and Photography, pains will be taken to avoid the employment of
all technical terms of which an explanation has not previously been given.
A SKETCH OF THE MAIN DIVISIONS TO BE ADOPTED, WITH THE PRINCIPAL
SUBJECT-MATTER OF EACH.
The title given to the Work is "A Manual of Photographic Chemistry," and
it is proposed to include in it a familiar explanation of the nature of
the various chemical agents employed in the Art of Photography, with the
rationale of the manner in which they are thought to act.
The division adopted is threefold:--
Part I. enters minutely into the _theory_ of Photographic
processes; Part II. treats of the _practice_ of Photography upon
Collodion; Part III. embraces a simple statement of the main laws
of Chemistry, with the principal properties of the various substances,
elementary or compound, which are employed by Photographers.
Part I., or "the Science of Photography," includes a full
description of the chemical action of Light upon the Salts of Silver, with
its application to artistic purposes; all mention of manipulatory details,
and of quantities of ingredients, being, as a rule, omitted.
In this division of the Work will be found nine Chapters, the contents of
which are as follows:--
Chapter I. is a sketch of the history of Photography, intended to convey a
general notion of the origin and progress of the Art, without dwelling on
minute particulars.