Part II.TONING
As distinct from tinting, a toned image consists of a color image embedded within a layer of colorless gelatine, so that while the highlights are clear, the shadows are colored.
The coloring matter may consist of an inorganic colored compound or a dye, or of a mixture of both, and by wholly or partially replacing the black and white silver image by one or more of these substances, a colored image is produced.
It is, of course, important that the colored compound should be as transparent as possible so that the full tone will be apparent on projection. In this respect, while some samples of toned film appear colored in the hand, they produce a substantially black and white image on projection, so that when judging any particular tone, it is absolutely necessary to view the image on the screen.
Of the various inorganic colored compounds, the metallic ferrocyanides are the most suitable for toning purposes of which:
Iron (ferric) ferrocyanide is blue,Copper ferrocyanide is red, andUranium ferrocyanide is reddish brown.
It is the object in toning to replace the metallic silver composing the image more or less by one of the above compounds or by a mixture of these. In this way intermediate tones are obtained.
Toning may be effected either by a single solution process or a two solution process.
Two Solution Process
This consists of first converting the silver image into silver ferrocyanide by a suitable bleaching bath, thoroughly washing, and acting upon the ferrocyanide image with a metallic salt, usually in presence of an acid, the metallicferrocyanide being produced by double decomposition. The reaction, however, is never complete, so that the image is mixed with undecomposed silver ferrocyanide which tends to make the image opaque, but at the same time it also adds “body” to the latter. Providing allowance is made in the original positive for this intensification, good tones are obtained. (See Tone G.)
Single Solution Process
Instead of the two separate baths used above, a single solution may be employed consisting of a metallic ferricyanide dissolved in a suitable solvent (say, an alkali salt of citric, tartaric, or oxalic acids) in presence of an acid and certain other salts.
On immersion of the positive film in this solution the silver image is converted to silver ferrocyanide, while the colored ferrocyanide is formed simultaneously and combined with it.
In either of the above cases in view of the fact that the metallic ferrocyanide is deposited in a colloidal condition in presence of the gelatine of the film, its state of division and the nature of the tone are usually affected by the presence of certain salts, changes of temperature, concentration of the baths and other factors which must be maintained constant in order to obtain uniform results. With such single baths it is possible to secure tones which are unobtainable by a two solution process, though as such single solutions are sensitive to light and rapidly attack foreign metals which may be present in the shape of faucets, etc., such solutions are comparatively unstable and require care in their use.
Owing to the limited number of colored inorganic compounds available for toning purposes, it is possible to obtain only a limited range of tones by the above methods.
In view of the possible wide range of colors obtainable by the use of dyes, it has long been considered that a satisfactory method of producing a dye image would be the ideal method for toning purposes.
As a result of recent work in our Research Laboratory, it is now possible to recommend such a method of toning which depends upon the fact that certain inorganic compounds, including copper ferrocyanide, have the propertyof mordanting certain basic dyes, so that when they are immersed in a solution of the dye the latter attaches itself to the mordant, which in turn becomes colored.
The most suitable dyes for dye toning are those which do not readily dye gelatine so that on immersing, say, a sample of copper toned film in a weak solution of the dye containing a little acid, the dye becomes mordanted to the image, while the highlights consisting of clear gelatine remain colorless, the resulting tone being a combination of the color of the toned film and the dye.
Full particulars are given under tones J, K, L, M and N.
Nature of the Positive to be Toned
Since most toning processes either intensify or reduce the original image, in order to obtain uniform results,commence toning with positive film of the correct density.
Three standards of positive film have been chosen: Thin, Medium and Normal. (See chart.) The “Thin” and “Medium” standards are obtained by giving a slight overexposure and a shorter time of development.
The exact degree of intensification which takes place in any particular case will soon be learned after a few trials.
Nature of the Developer
Any good Elon-Hydrochinon, Kodelon-Hydrochinon, or straight Hydrochinon formula will give satisfactory tones, though in the case of Tone G an Elon-Hydrochinon developer is essential in order that a rich olive color may be obtained.
For toning, it is necessary that the developed film should be entirely free from fog, since a thin veil becomes intensified in most of the toning processes. Fog may be caused by:
(a) Oxidation of the developer, noticeable by the brown coloration produced after continued use. The remedy is to renew the developer.
(b) Carelessness in compounding the developer. The usual mistake consists in adding the carbonate to the Elon and Hydrochinon without previously adding a portion of sulphite to prevent oxidation. It is not advisable, however, to add the whole of the sulphite to the Elon and Hydrochinon in the first place, otherwise the Elon may precipitate.Mixing the developer with water which is too warm will often cause fog.
(c) The presence of copper, brass, and tin, the fumes from sodium sulphide, etc., in the developing baths are to be strictly avoided. A salt of copper if present only to the extent of one part in 10,000 will produce fog on cine positive film.
Fixing
This operation should be complete and, if possible, carried out in two consecutive baths and followed by thorough washing, otherwise uneven coloring will result.
In order to eliminate any possibility of uneven toning it is always advisable to tone immediately after washing and before drying.
Control in Toning
As in the case of tinting, the nature of the tone obtained with the various solutions depends on the following factors:
a.The nature and dilution of the toning solutions.Except in those cases where it is recommended to revive the bath by adding more acid, it is not advisable to modify the composition or dilution of the various solutions, as these have been adjusted to give the best results.
b.Temperature of toning.
In most cases a change of temperature from 60 to 70 degrees F. has merely the effect of changing the time of toning. It is advisable, however, to maintain the temperature of the various solutions between 65 degrees and 70 degrees F.
c.Time of toning.
Except in the case of tones F and G when toning proceeds to a limit, the nature of the tone produced varies with the time of toning, reaching a limit in from 10 to 15 minutes, so that in a shorter time intermediate tones are produced. Since most of the toning processes intensify the original image, if an intermediate tone is required, it is usually necessary to commence toning with denser film than when toning is to be carried to the limit. See tones B, C and D.
When producing intermediate tones, it is therefore possible either to tone in the normal bath for a given timeor in a diluted bath for a longer time. In order to reduce the number of individual toning baths to a minimum it is recommended to vary the time of toning rather than to vary the dilution of the bath and to judge the tone by inspection. Since the strength of the toning bath falls off with use, inspection is necessary in all cases except Tones F and G.
Before commencing work with any bath, it is advisable to make a test on a short length of film.
Permanency of Tones
The permanency of the tones produced largely depends on the care exercised throughout the various operations.
The silver sulphide image may be considered permanent, though in the other cases, where more or less silver ferrocyanide is present, the toned image is not absolutely permanent, being somewhat soluble in hypo and affected by fumes of sulphuretted hydrogen.
In the case of the iron and uranium tones, the colored ferrocyanides are dissolved by alkali such as sodium carbonate, so that the toned film should not be washed for too long a time in water which is at all inclined to be alkaline.
In no case however, if the instructions are carefully followed will the toned image deteriorate during the active life of the film. Moreover, so far as can be ascertained, the wear and tear of film which has been toned by the methods recommended is in no way impaired, though by virtue of the hardening action of most of the toning baths on the gelatine it is advisable, especially during the winter months, to immerse the film for three or four minutes in the usual 2% glycerine bath after toning.
Should film have to be stored for long periods of time, toning is inadvisable, nor is it advisable to tone valuable film unless duplicates are available.
Thelifeof the toning bath has been carefully investigated in each case, the term “life” being considered as the total length of film capable of being toned by a given volume of fresh solution when toning is conducted continuously and without interruption.
In all cases it is false economy to exhaust a toning bath to the limit and thus obtain inferior tones, since the cost of the chemicals employed is insignificant compared with the value of the film being treated.
Since the figures given represent the capacity of the bathfor toning under the best conditions, they only apply providing the baths are kept covered as far as possible when not in use, to exclude light, and providing no foreign metallic surface, however small, is allowed to come into contact with the solution.
As mentioned above, single solution baths are not intended for occasional use. In such cases two-solution methods should as far as possible be employed, although it has only been possible to recommend the latter for the production of sulphide and blue-green tones.
Stability of the Solutions
All toning solutions containing potassium ferricyanide are sensitive to light, the ferricyanide being reduced to ferrocyanide. Therefore when not in use the tanks should be carefully covered so as to screen the solutions from sunlight.
It is also very important that no metallic surface however small should come in contact with the solutions; any metal pegs on the racks or pins used to hold the film together will gather the tone in preference to the film, causing the formation of sludge. Plain wooden racks with or without wooden pegs should be used, and metal faucets replaced by wooden plugs.
If any considerable amount of sludge forms in the tank at any time, it is due either to incorrect mixing, the action of light, or to the presence of foreign metallic substances.
Tone ARed (Copper)
Positive Employed—Normal
After immersion of the well washed film in water for one minute, bathe in the following:
Dissolve each ingredient separately in as little water as possible, mix the filtered solutions so obtained in the order given, and dilute to the required volume. The solution obtained should be light green in color and perfectly clear. The ammonium carbonate should be almost transparent and free from white powder, and should be dissolved in coldwater, while the ammonium citrate employed should be neutral. Most samples contain acid, which acid would neutralize the ammonium carbonate and affect the resulting tone. The free acid is usually citric acid, and should be neutralized with a solution of ammonia using litmus as indicator.
Temperature of Toning—To obtain the best results the temperature of the bath should be from 65 degrees to 70 degrees F.
Time of Toning—Five to ten minutes.
Time of Washing—10 minutes.
Life of Bath—With use the bath precipitates a brown sludge of copper ferrocyanide, and in consequence becomes weaker by virtue of the loss of copper, though 50 gallons of the solution will tone about 10,000 feet of film.
It is necessary to keep the film entirely submerged in the tank, or constantly in motion when on the drum, otherwise if the film is frequently examined, especially during the first few minutes of toning, streaks are liable to occur.
Tone BRed (Uranium)
Positive Employed—Thin.
Immerse the well washed film in the following:
Mix in the order given. The solution obtained should be perfectly clear and pale yellow in color.
In view of the fact that the nature of the tone is influenced largely by the acid content, it is very important that the uranium nitrate should contain no free acid, and this may be assured by neutralizing a solution with dilute ammonia until a slight permanent precipitate is obtained.
It is convenient to keep stock solutions of the above (say, 10% solutions) from which a new bath may be expeditiously compounded. A 10% hydrochloric acid solution is one containing 10 parts by volume of the concentrated acid per 100 volumes of the final solution.
Temperature of Toning—65 degrees to 70 degrees F.
Time of Toning—Ten minutes.
Since this and the following single solution methods of toning produce a marked intensification of the silver image—which intensification increases with the time of toning—it follows that the nature of the tone changes with time also.
The composition of the bath has been so adjusted that the maximum effect is produced in about 10 minutes, the tone passing through a series of changes from brown to red during this time.
It is therefore possible to obtain intermediate tones by withdrawing the film from the bath at shorter intervals, though in such cases the contrast of the original black and white film should be adjusted accordingly, since with slight toning very little intensification takes place. (See tones C and D.)
Time of Washing—Ten to fifteen minutes.
The highlights will become clear in the above time, though a thin yellowish brown veil may remain in the clear gelatine as a result of the intensification of minute traces of fog, but this has no effect on projection. If the bath is working correctly the yellowish veil is only just perceptible, but if appreciably visible, then either the film was fogged during development, or the bath was not compounded correctly. Washing should not be carried out for too long a period, especially with water inclined to be alkaline, because the toned image is soluble in alkali.
Life of Bath
Fifty gallons of solution will tone about 5000 feet of film without any appreciable change in the tone, after which the rich tone tends to flatness as a result of a deficiency of acid in the bath. At this point the bath may be revived by the further addition of acid to the extent of the original amount, when a further 5000 feet may be toned. At this stage the richness of tone falls off rapidly and the bath should be thrown away.
Used intermittently over a period of several days the life of the bath is approximately the same.
With continued use a slight brownish flocculent precipitate may form in the bath, but this should only be slight, otherwise it is caused by incorrect mixing, the action of light, or by contact with a metallic surface.
Tone C—Red Brown (Uranium)
Positive Employed—Medium
The toning formula employed and the instructions to be followed are the same as for Tone B, the time of toning being about 5 minutes at 65 degrees to 70 degrees F.
Tone D—Brown (Uranium)
Positive Employed—Normal
The toning formula employed and the instructions to be followed are the same as for Tone B, the time of toning being about 3 minutes at 65 degrees to 70 degrees F.
Tone E—Sepia (Uranium and Iron)
This particular tone is obtained by suitable mixture of red and blue toning solutions. By varying the proportions of these baths, tones varying from red to sepia may be obtained.
The following is only one of the many tones produced by this method. Increase in the proportion of the iron bath makes the tone colder, and vice versa.
Positive Employed—Medium
Immerse the well washed film in
Solution for tone B (red brown) 5 vols.Solution for tone H (blue) 1 vol.
Time of Toning3 to 4 minutes at 65 degrees to 70 degrees F.
The instructions regarding method of procedure, life of bath, etc., are exactly the same as for tone B.
Tone F(Sulphide)
Positive Employed
With a thin positive a warm brown tone is obtained, while with denser film the effect is that of a blue-black tone.
A trace of iron in the sodium sulphide will do no harm providing the solution is boiled and the precipitated iron sulphide allowed to settle before use. The well washed positive is thoroughly bleached in A, washed for 5 minutes, and immersed in solution B until the film is thoroughly toned.
Temperature of Toning—65 degrees to 70 degrees F.
Time of Toning—Four to five minutes.
Time of Washing—Ten to fifteen minutes.
Life of Baths
The toning baths A and B are comparatively stable and will keep until exhausted.
Tone G—Olive Green (Iron)
Positive Employed—Thin to medium.
The best tones are only obtainable on film developed in an Elon-Hydrochinon developer. Thoroughly bleach the well washed film in:
Time of Bleaching—Two to five minutes.
After washing for 10 to 15 minutes, tone in the following at 65 degrees to 70 degrees F.:
Time of Toning
Toning should be complete in from 3 to 5 minutes.
Time of Washing—Ten to fifteen minutes.
If the highlights are stained blue, or if the image will not completely tone in the shadows, this is due toinsufficient washing after bleaching. When bleaching, it is important to examine the film as little as possible, otherwise streaks are liable to be produced due to the action of the air at those parts where the solution drains off the film. It is also important to tone immediately after bleaching and washing.
Life of Baths
Bleach A.
Providing the solution is screened from the light and kept covered to prevent the undue escape of ammonia, the bath keeps fairly well, but if it shows any signs of weakening, it should be revived by the addition of a further quantity of ammonia equal in amount to that originally used. If so revived at intervals, 50 gallons will bleach 40,000 feet of film before exhaustion.
Solution B.
Fifty gallons of solution B will tone 30,000 feet of film without further addition of acid, when it should be thrown away.
Tone HBlue (Iron)
Positive EmployedThin or Medium, according to result desired.
Tone in the following:
The method of compounding this bath is very important. Each of the solid chemicals should be dissolved separately in a small quantity of warm water, the solutions allowed to cool, filtered into the tank strictly in the order given, and the whole diluted to the required volume. If these instructions are followed, the bath will be a pale yellow color, perfectly clear, and will remain so for a considerable period.
Time of Toning—Five to ten minutes at 70 degrees F.
Time of Washing
Wash for ten to fifteen minutes until the highlights are clear. A very slight permanent yellow coloration of the clear gelatine will usually occur, but should be only just perceptible, when it will have no effect on projection. If the highlights are stained blue, then either the film was fogged during development or the bath was not compounded correctly. Washing should not be carried out for too long aperiod, especially with water inclined to be alkaline, because the toned image is soluble in alkali.
Life of Bath
If the acid is renewed to the extent of the original amount after toning each 5000 feet, the bath is capable of toning 15,000 feet per 50 gallons of solution.
If even after revival, the tone remains flat, the bath is exhausted and should be thrown away.
After continued use, a slight bluish sludge will collect in the bath, but this is not harmful. Should this form, however, to any appreciable extent, it is due either to incorrect mixing, the action of light, or to contact with metallic surfaces.
Tone I—Pale Blue (Iron)
The instructions are as for Tone H with the following modifications:
Positive Employed—Normal.
Time of Toning—Two to four minutes according to depth of tone desired.
Tone J—Red (Dye Tone)
By first toning in Tone A, washing, and then immersing the copper toned film in an acid solution of a basic dye, the dye is mordanted to the toned image, thus modifying the color.
Nature of Positive—Medium
Tone for five to ten minutes in solution as for Tone A, and after washing for ten minutes immerse in the following dye-bath.
Time of Toning
Five to ten minutes, according to depth desired.
Temperature of Toning—65 degrees to 70 degrees F.
Time of Washing
Usually only a slight rinse in water is necessary. If the highlights are stained, the film should be washed for five or ten minutes or until clear. Stained highlights are caused either by insufficient washing after toning, too strong a dye-bath, or an incorrect amount of acid in the dye-bath.
Tone K—Orange (Dye Tone)
The instructions are exactly as for Tone J, substituting the following dye-bath.
Tone L—Violet (Dye Tone)
The instructions are exactly as for Tone J, substituting the following dye-bath:
Intermediate Dye Tones
The depth of the dye tone is determined by the time of immersion both in the copper toning bath and in the dye-bath. Pale tones may therefore be obtained either by giving a short bath in Tone A and fully dyeing, or by toning for a longer time and giving a short immersion in the dye-bath.
By mixing the dye-baths J, K, and L in varying proportions intermediate colors may be obtained just as in tinting.
Tone M—Pale Red (Dye Tone)
Positive Employed—Normal
Tone for one to two minutes in Tone A, wash for ten minutes and then immerse in the following dye-bath.
Dye solution for Tone J, one volume.Dye solution for Tone K, one volume.
When the desired tone is obtained rinse until the highlights are clear.
Compound Tones
Tone N—Copper-Iron-Dye Tone.
By first partially toning the black and white film (Medium) in Tone A for three to four minutes at 65 degrees to 70 degrees F., so that the half-tones are completely toned but the shadows only partially, washing for ten minutes and then completing the toning process in the blue toning bath H, the residual silver in the shadows is toned blue. In this way a double tone is obtained, the shadows appearing dark blue and the half-tones reddish brown.
By immersing the film toned in this manner in the Chrysoidin dye-bath as given under Tone K, the dye is mordanted to the half-tones which contain copper ferrocyanide, producing the effect indicated.
Combined Tinting and Toning
In many cases pleasing effects may be obtained by tinting film which has already been toned, the result being that the clear portions or highlights assume the color of the dye, while the shadows and half-tones project a tint intermediate between that of the dye and the toned deposit.
Considerable judgment is necessary, however, in choosing suitable tints to blend with any given tone.
The most successful combination of toning with tinting is in the production of sunset and moonlight effects over water, by first toning blue and then tinting orange, red or yellow.
The following combinations will cover most cases required:
Tones A, B, C, D, E, F, J, K, L. Tints Nos. 2, 5, 6.
Tones G, H, I. Tint almost any delicate shade.
It is considered unnecessary to illustrate every combination of tone and tint above, so that only typical examples are given. It must be noted that toned film (except tones A and F) absorbs the dye more quickly than untoned film, so in order to duplicate appended samples, the dye-baths should be diluted accordingly.
Very pleasing effects may also be obtained by locally tinting toned film, the color being applied either by hand with a brush, or by stencilling.
Equipment
The equipment necessary for systematic tinting and toning is essentially the same as that required for development, consisting of the usual tanks and racks or small drums, only it is advisable that they should be used for this purpose exclusively and, if possible, occupy a separate room to exclude any possibility of contaminating the developing solutions by the copper or sulphiding bath, which would cause development fog immediately.
The “drum” system, on account of the expense involved in apparatus and the larger space required for manipulation, is not to be recommended for tinting and toning operations, though for operation on a small scale, a small wooden drum revolving in a shallow wooden tank is most efficient and economical.
When the tank and rack system is employed, the tanks should be of slate or other resistive material, and have an outlet at the bottom in the form of a hard-rubber stopcock or a plain wooden plug. The racks or drums may be of wood, but if metal pegs are employed on the racks they should be coated with acid-resisting paint such as asphalt, since the presence of any metallic surface in the toning baths will cause contamination and effect a precipitation of sludge. The frames should not be interchanged but kept separate either for tinting or toning to prevent contamination of one bath with racks previously employed in another. This also applies to the small drum system. For instance, a pink tint would be ruined by using a rack which had previously been immersed in a deep blue dye-bath, unless that particularrack had been thoroughly washed. In the case of delicate tinting, however, no harm is done providing the racks have been previously coated with the following waterproof varnish:
Before treatment it is preferable to immerse the racks which have been previously used for developing, in a 1% solution of hydrochloric acid for two or three minutes, wash for fifteen minutes and thoroughly dry. The well-dried racks are then dipped in the above solution and the excess liquid drained off, when the varnish dries almost immediately. The varnishing should be repeated at intervals.
Mixing Solutions
Developers, toning solutions and dyes should be mixed in crocks of glazed earthenware or enameled iron, using warm water where necessary and ensuring thorough solution by stirring with a wooden paddle, which should be thoroughly washed after each operation. Having thus dissolved the chemicals in as small a quantity of warm water as possible, filter through fine muslin and make up the bath with cold water, so that the final solution will be at approximately the correct temperature.
The chemicals employed should be pure (for the samples, “EKCo.” tested chemicals were used), and in cases where a good water supply is not available, only distilled water should be used.
Troubles in Toning
Most difficulties met with in toning may be traced to one or more of the following causes:
Uneven Toning
This may be due to:
a. Grease on the film. Never project film before tinting or toning.
b. Drying spots on untoned film. If possible, always tint or tone film immediately after washing and before drying.
c. Examination of the film too frequently during toning, causes an oxidation of the toning solution in places where the solution fails to drain from the film.
d. Insufficient or uneven washing of the film after bleaching and before toning (Tones F and G).
White Spots
White spots are produced by particles of hypo or carbonate dust or splashes of a solution of these, settling on the toned film. The toned image consists of silver together with more or less silver ferrocyanide and the ferrocyanides of uranium, iron and copper as the case may be. Silver ferrocyanide is soluble in hypo while uranium and iron ferrocyanides are soluble in a solution of sodium carbonate, strong ammonia, etc., so that the white spots indicate those parts where the toned image has been dissolved away.
Irregular white spots may also be formed if the film is imperfectly squeegeed after washing and before drying, especially if the wash water is slightly alkaline. When a spot of water on the toned film evaporates, the small amount of alkali present in the water becomes more concentrated and finally dissolves away more or less of the tone, leaving a white spot on the film.
White spots due to these causes may be prevented by immersing the film for a few seconds in a .5% solution of glacial acetic acid after toning and before placing on the drying rack.
Stained Highlights
Are caused by:
a. Traces of fog on the film before toning.
b. An improperly compounded toning bath. All solutions when new should be perfectly clear.
c. Premature exhaustion of the bath. This is due either to the action of light or to the presence of some metal in the tank in the shape of screw heads, faucets, pins, etc., which gather the tone and cause the formation of sludge.
It is important to keep all solutions containing potassium ferricyanide exposed as little as possible to daylight, to use only wooden racks with wooden pegs, and to cover all metal parts very carefully with acid resisting paint.
d. In dye-toning, stained highlights are due either to insufficient washing after toning with copper, too strong a dye-bath, or an incorrect amount of acid in the dye-bath.
Tints