US 2236417 A
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Description (OCR text may contain errors)
Patented Mar. 25, 1941 UNITED". STATES 2,236,417 raocsss or rnonucmo oononnn rmn'rs Joseph F. Spalnhour, Jr., Morganton, N. 0., assignor of one-fourth to Nelson J. Jewett, Arlington County, Va.
No Drawing. Application February 23, 1939, Serial No. 258,057
The invention relates to colored photographs and has as an object the provision of a process of dyeing photographic prints and transparencies. 7
It is an object of the invention to provide a process of dyeing image bearing photographic coatings in such a manner that the taking of the dye shall be influenced by the intensity of the silver deposit in the coating.
It is a further'object to provide a process of the character referred to whereby a plurality of dyes may be applied to selected areas of the print.
It is a further object of the invention to provide a method of preparing a print for coloring by subjecting the same to a process of induration or aging by natural or artificial means. I
It is a further object to provide a method of controlling the dyeing of a print by subjecting a wash out relief print to a hardening treatment.
Further objects will appear from the following description of illustrative steps and alternative steps of the process of the invention.
By the term print as used herein and in the 25 claims is meant a photographic positive or negative whether carried by paper or by a transparent medium as glass or Celluloid.
As described the invention depends on the treatment of a gelatino-chloride emulsion that has been printed under a negative. Best results have been had with the type of unwashed emulsion containing swellable water-soluble gelatin in generous amount. Best results have been had with thetype of emulsion with which the Agfa proof paper is coated, comprising unwashed and comparatively freshly coated-emulsion coatings of the type capable of being printed-out to images of great intensity.
It does not matter what kind of emulsion is used in the making of the negative from which the print is made, whether panchromatic or color blind, but it is preferable to use a negative with ample contrast. As will be seen from what follows it is possible to exercise a limited control of the color areas by exposing through color filters in the production of the negative, and also by composite printing through a plurality of negatives.
The print is conditioned for treatment by induration or aging. Thus the same may be printed in the usual manner by exposure to day light or artificial light and may be laid away for a period of weeks or even months before further treatment. During natural aging the image area gets progressively harder but the whites or high lights of the print are sumcien'tly less hardened to remain soluble whereby a washout relief may be produced. A print to be so treated need not be printed excessively.
For treatment by the artificial aging process it is important that thenegative used shall be contrasty and the "shadows should be so thin that print can easily be read through the clearer portions of the negative.
The artificial aging is had by the application of heat to the exposed print. The print may be produced in the usual manner by exposure to day light or artificial light and may then be pressed with a sad iron which becomes increasingly hot during the pressing until it is "hissing ho only, being protected from direct contact with the hot iron when the iron is applied to the emulsion side.
The artificial aging may be carried out simultaneously with the exposure of the print through the. negative by exposure to both light and radiant heat. This is the method at present preferred as it is more susceptible to standardization. Dual exposure to heat and light may be had by exposing the print to the light of a hot yond the point which is sufliclent with the natu-' ral aging method and may be gauged by inspecting the color of the print. Printing should foe carried to the point of marked solarization"j of the shadow areas which those skilled in the art will understand to be indicated by the presence of metallic bronzing or iridescence of the deepest portions of the print.
The aged print will consist of gelatine which is still soluble in the surface of the high lights and progressively less soluble toward the image and shadow portions. The process proceeds with the production of a wash out relief. Usually water alone is sufilclent to dissolve the gelatine in the surface of the high lights and the washing ofi of gelatine should not remove all of the gelatine even in the lightest portions. The wash oil may be controlled by the temperature of the water and the force and time of its applications with most prints of properly aged conditionit is advantageous'to apply brief washes of tepid water alternating with cold water and finishin with cold to check the action. The temperature of the warm wash is adjusted to the condition of the print. Usually higher temperatures are required with storage aged prints than with heat aged, although it is possible to artificially'age a print so that it will act precisely like the storage aged. In case the aging is such that water alone is found ineffective to dissolve the gelatine in the high light or intermediate tones. the first water bath may be slightly acidified as withsulphuric acid.
when storage aging is excessive to an extent which prevents the formation of a wash-out relief effected with plain water, such too-muchaged prints may frequently be "saved for dyeing by using slightly acidulated water for the primary bath (as water acidulated with sulphuric acid, which is a gelatin solvent) to make a wash-out possible, in which cases a very thorough rinsing of the relief prints must be performed before the tannic acid bath; such prints may exhibit surface wrinkles after the tannic acid bath; another peculiarity of such over-aged storage prints is that sometimes dye number one will not take in the extreme highlights, and that dye number one will sometimes taken in an intermediate deposit area apparently unaffected in the washout, the latter especially if the dye is such as Victoria Green and is acidulated with sulphuric acid, its color being revived after application by a cold water rinse. Generally such excessive storage aging as calls for this special treatment is, however, undesirable, since the results are inferior.
The best theory upon which I am able to explain the action of the aged gelatine of the print, whether artificially aged by heat, or naturally by storage, is that the by-products of the light reduction of the silver salts in theemulsion harden the gelatine during the aging process, and the hardening action depends upon the amount of such by-products and upon the time and conditions in which they are permitted to act, their action being greatest in the deepest shadows.
The wash out relief may not exhibit any marked swelling or raising of the shadow areas, particularly in the case of storage aged prints.
After preparation of the wash out relief the still wet print is bathed in a solution of tannic acid. The solution is desirably though not necessarily a saturated solution, and pure tannic acid is preferable. The effect of the tannic acid is powerfully astringent on the surface, acting progressively on the surface, minimizes staining and tends to make the image areas reject the dye which is first applied to take on the washed out areas or whites.
The tannic acid bath may have a small amount of sodium sulphite added thereto, in quantity insuillcient to appreciably lessen the acidity of the bath. The tannic acid bath will produce a bluish tint in the areas of intermediate deposits in the case of artificially aged prints, the presence, and intensity of the tint being made a measure of the sufficiency of the tannic acid treatment for the purp ses of the two color Auramine dyeing quent dyeing.-
hereinafter described. The sodium sulphite ad- .dition has the effect of retarding oxidation.
Perhaps the most outstanding feature vof the process is that the "whites" or high lights may be dyed seleotivelmthat is to say, they maybe dyed with ftake elsewhere on the print.
a suitable dye color which does not Whenever it is desired todye this whitearea,it is always dyed immediately after the tannic acid bath. However, a quick preliminary cold water rinse to free the surfaceof tannin bath and for the added purpose of preventing the precipitation of the dyes in the instances of those suitable dyes which are precipitated by tannic acid. For this reason I have termed whatever dye is "dye number one, and this "whites" area or high light area I have termed the ".area' of dye number one."
Victoria Green isa good example of a dye for this area. I: it should so happen that'no dyeing,
is desired in this area,this.dyeing*is of course been performed Just the sein .both to condition this area so it will reieo 'tlyesthat may r" sequently, applied to other 'partsof, the print-and to condition 'other parts of the print for Dye number one, and in fact'all dyes applied by the process, are applied to a wet surface, and an evenspread of the dye solution'itofurther insure, even "taking maybe accomplished by movement. 'Application' and taking of ailTdyes involved in the process is usually only a matter 'of moments, often practically instantaneous; In
experimenting I have usually applied'the dye solutions by dropping them, say with a medicine dropper, on the wet surface .of the. print held in the hand. The superfluous dye is rinsed of! under a stream of cold water. By dye solutions I of course'mean dilute dyesolutions, diluted to the desired color density, water being the medium. a
At this stage. that is. Just after the application of dye number one (or in case no color is desired in the area of dye number one,; then just after the tannic acid bath). the print is suspended and allowed to drain and dry thoroughly.
Now, if it is not desired to perform fiuther dyeing, the print is regarded as finished, unless it is preferred to change the color of the red tanned shadow or image area to a brown color by fixation with a bath of weak plain hypo (unacidulated) i However, if further dyeing is desired, the next dye applied is applied during or immediately following a bleaching and fixing action, and is termed dye number two." The area of this second dyeing, that is, 'of dye number two, is usually all of the image or deposit area, and when such is the case I apply a little plain sodium thio-sulphate (pea crystals or granulated) to the water-wetted surface of the print-having first dipped the dry print in water and lifted it carefully out to a horizontal position on the palm of the'hand, keeping as much water on its surface as possible. As the hypo begins to dissolve, I drop about 2 to 4 drops of about 15 per cent sulphuric acid into this surface bath. Now the deposit area gradually bleaches leaving a slight residual image, especially if sodium sulphite was absent from the tannic acid bath treatment earlier given. It seems that the sulphur dioxide generated thus on the print effects the bleaching, but of course does not bleach any stain image produced in the tanning bath. Dye number two may be dropped on during the action of this 2.0 omitted. but the tannio acid bath should have j-f T dye take" evenly and until the dyeing is seen to be sufficient, and then the print is rinsed under cold tap water and again suspended to drain and dry.
If no further dyeing is desired, the print is now flnishedbe ing a two color print, one color in I the wash-out area and the other in the image area not affected in the wash-out of the relief.
While I have found the above bleaching method generally the most useful and satisfactory, the invention is not limited to this or any particular bleach since others may'be'used, and indeed some dyes can be applied selectively with nothingbut the plain hypo fixing bath. An instance of another bleach that can be used is hydrogen dioxide solution to be followed by fixation in a plain hypo bath.
If it is desired to apply an additional dye, it may be termed dye number three, and is in fact the third in order of application. The print is conditioned for this third dye by brief soaking or rinsing in cold Water, followed by'brief immersion in a weak bath consisting of water containing dilute sulphuric acid. Dye number-three is dropped on the horizontal surface of the emulsion as the print is held face up on the palm either still wet with a superfiuity of said bath or of a subsequent cold water rinse, and takes progressively in the shadow area, commencing with the area of greatest original density, and may be stopped at the desired point by rinsing off with cold tap water. For example if the shadow area was made red by a dye number two such for example as Fast Crimson, then a dye number three such as Victoria Green will make the densest shadow part thereof virtually black. Dye number three is thus added to dye number two in said part.
However, if dye number two is a dye reducible with sulphuric acid, or affected by sulphuric acid as is, for. example, Victoria Green, it follows that the application of dye number three as described to a part thereof amounts to a replacement or substitution, provided dye number three used was not also thus reducible, the densest area of original deposit losing the color of dye number two and taking on the color of dye number three. At this juncture it is well to note that the successful application of dye number three seems to be conditioned upon a somewhat greater minimum of aging than is the application of dye number two, since sulphuric acid used in said bath in connection with the former has the softening influence of a solvent for gelatin; hence insufficient aging or tanning for dye number three results in the said dye taking progressively in the high 1ights, commencing with the parts of least or no original deposit, for example Fast Crimson will thus replace Victoria Green progressively.
The print may now be considered finished after it is rinsed in cold water and suspended and dried (drying is very rapid with these color prints and is preferably in atmosphere not exceeding 80 degrees); however at any stage at which a dry color print is considered finished, the brilliance and beauty of its colors may be greatly enhanced by the application of a coating of any good transparent waterproof print varnish, for example Eastmans Nepera waxing solution, as a final step.
Having summarized the major feature of the process, it remains to summarize a special method of producing a three color print with only two dyes, as for instance one of them being the yellow dye, Auramine. Auramine is applied as dye number one, as described above, except that,
in the case of storage prints there is a preliminary dilute ammonia rinse (about 2 drops of stronger ammonia to the quart of water), followed by amomentary cold water rinse, just before the tannic acid bath, said tannic acid bath then causing a bluei-ng oi the lesser densities (intermediate area). In the case of artificially aged prints this desired blueing of. the lesser or intermediate densities of deposit will similarly occur in the tannic acid bath without the ammonia bath being used, by proper manipulation in the dual printing exposure and proper tanning.
I have also found that it is possible to use other color solutions which will even develop color in the wash-out area different in color from the dye solution applied thereto to produce same. All dyes used in this invention are applied in a plain water medium unless otherwise indicated.
.The auramine takes in both the whites" and in the area of lesser or intermediate bluish deposit, but not in the deepest deposit or shadow portion of the image. The print is then rinsed in cold water, dried thoroughly, and-then rinsed again before immersion in an exceedingly weak plain hypo bath which fixes (fixation is here visible as always with these printing-out photos) which fixes only said deepest deposit or shadow portion of the image, and apparently does not affect the bluish intermediate or lesser density area, which bluish area, by the way, has now become greenish due to the taking of the yellow auramine dye solution; the print is now taken in the left hand with some of the said bath on its surface into which a few drops of dilute sulphuric acid (roughly about per cent) is dropped, and the strength of this surface bath is increased by making a bleach as described above in connection with dye number two, the deepest shadow portions (which are fixed with plain hypo as described above) browning, darkening, and then bleaching, while the intermediate or greenish parts become green or yellow green, apparently becoming bleached also of their original deposit, and become green or yellow green, apparently by some hardening combination of the yellow dye and that developed .bl ue which made said area look bluish before it was bleached. This greener yellow green area is insoluble in water. The high lights are auramine yellow, The yellow and green blend gradually into each other, that is to say, there is no sharp line of demarcation between them. Any dye number two may be applied thus, and the application is either during or immediately following the bleaching and will take" only in the fixed and bleached deepest shadow area which was, by the way, approximately the area which acquired the solarization iridescence in the printing-out. The print is now rinsed in cold water and suspended and dried. Fast Crimson works well as a dye number two in this area and accentuates the green by color contrast. Thus with auramine the high lights are yellow, the lesser shadows are green, and the deepest shadow is the color of whatever dye number two is applied thereto, for example, Fast Crimson.
Dyes tried showing varying suitability for dye number one area include Victoria Green; Auramine; Safranine A; Napthalene Green; Fast Crimson; Methyl Orange; Formyl Violet; Acid writing inks such as Parker's Quink. Dyes showing more or less suitability for dye number two area (and hence for dye number three also) include Fast Crimson; Auramine: Victoria Green; 5 Naphthalene Green; Safranine A; Methyl 0range; Wool Yellow; Magenta; and writing such as Parker's Quink (Green, perm.), and especially Watermans Spanish Tile, and Watermans Aztec Brown.
The process of the invention will be understood in principle and application from the above disclosure. There are many minor variations which I have tested and many capabilities aside from those already mentioned.
It has been stated that the areas to which the dyes will take may be profoundly affected by exposure of the negative material by known color separation methods, or incorrect rendering of color values. It will be observed that if three prints are made from color separation negatives, two of them being carried by transparent sheets, the prints may have their image areas dyed with colors complementary to the taking filter and upon superposition will provide a print in natural colors.
The disclosure of application of tannic acid solution is for purposes of illustration.
Instead of a single dye, mixed dyes may be used for the first, second," or third dye.
In the application of the second dye during bleaching, the print may be rinsed when the dye has taken on only the most dense deposit areas, and a different dye may be applied to take in the intermediate deposit areas. If the said differ- 35 ent dye does not take properly the print may be further bleached with sulphuric acid-dilute and hypo as before described, accompanied by the application of the difierent second dye. Also two dyes may be applied to the area of greatest deposit differing in nature to such an extent that they will take in different degrees depending on the differing amounts of deposit in that area.
The print may be hardened or tanned then treated with dilute sulphuric acid followed by a treatment with unacidulated hypo mixed with a methyl orange dye. The print after rinsing is treated with tannic acid solution mixed with a green dye as mentioned in connection with dye number one. As a result the heavy deposit areas will have the greenish yellow of the bleached image and the lighter deposit the red of the methyl orange, the lighter deposit of the washed oil area appearing green or blue, with the whites .practically unaffected.
Still further, the hypo during the bleach may contain methyl orange and as a result the whites will remain white, the deposit area of the wash off areas will take the methyl orange, and the 60 deepest deposit not included in the wash oi! will have the greenish yellow caused by the bleaching.
Excessive storage aging may cause dye number one to take only in the area of lesser deposit which is included in the wash-out, the parts of 5 the wash-out area containing little or no deposit remaining undyed.
In the two dye process it is easy to allow a little oi dye number two to replace dye number one in the lightest or unaffected parts of the wash 70 off areas, thus getting an effect of three colors from the two dyes.
The first dye, after tanning, may be applied in dilute sulphuric acid. If green, as Victoria Green, is thus applied in dilute sulphuric acid the 75 dye will be changed to yellow to take in the high lights. A rinse in cold water revives the original color.
After dye number one has been applied, following tanning, one part of formaline to twenty parts of water may be fiooded on the print and rinsed off, when the dyed area will be found practically insoluble. The unwashed off area may then be rubbed off with a smooth implement, as the tip of a finger, after which, rinsed, and another dye applied to take in the rubbed of! area. The rubbing is an alternative for bleaching for the application of dye number two. It will be seen that various areas may be rubbed off and a number of dyes applied as dye number two. The application of formaline is not essential but is preferred and the iormaline may be applied after each rubbing off of diiferent portions. By the rubbing of! procedure any number of-dyes may be applied to segregated areas of the print. As in all of the applications of dyes by the method of the invention, the dyes take very quickly and but a short time is necessary to produce beautifully colored prints.
Supposing that it is not desired to represent in graduations of one color the image or deposit area of the negative, wholly. or in part. There are several alternatives, five of which I will mention: first, the prints can be made from a film positive (or direct positive), which reverses the order, the sectional dyeing being done in the area represented by deposit on the original negative, and the graduated monotone being in the area represented by the clear oi the original negative; second, a slight general exposure of the print containing the image may be performed before the artificial aging so as to facilitate an only partial wash-out of the whites, the "whites not being washed out being left for sectional coloring by the rub-off method in the same manner as the image areas; third, inequalities in deposit in various parts of the inverse image area make it easy to stop the washout when only the whi parts ireest of deposit have been eliminated by the alternating dilute sulphuric acid and warm water treatment forming the relief, leaving the whites" parts less free of deposit to be. colored sectionally by the rub-oi! method described above; fourth, density may be added by retouching parts of the "clear" of the negative, or of the film positive, to throw parts into the monotone area or into the sectionalcoloring area as desired, or, less efliciently, by retouching the individual prints locally in parts of the whi before artificial aging, by means of a point of light, or some form of light exposure; fifth, the use of a color filter when the picture is taken, which is described in detail below:
The usual scale of negative density is satisfactory since all of the print area is in either the graduated-monotone area or the sectionaldyeing area, with no middle ground. However. during the formation of the relief as described above on a print made from a negative having a complete scale of density or graduated density, it will be seen that the elimination of gelatin on the ensuing print must be watched more closely than is necessary when the negative has considerable contrast with little or none of what may be called intermediate density.
Now it is evident that when a color filter is used, the densities on the ensuing negative will be practically the same as those visible to the photographer if he looks at the object or view to be photographed through the color filter, parobject or view being photographed. A color filter used when theexposure is made will serve to determine the position of at least one color reflectance as it is represented in terms of density on the ensuing negative; that is, to determine whether that reflectance is to be represented in the area of graduated-monotone or in the area of sectional-dyeing. For example, a reflectance which is decidedly of one color, or not .very impure, probably will by the use of a filter of that a color be represented on the ensuing negative by sufficient deposit to represent that reflectance in the print area for sectional-dyeing; and, contrawise, the use of a filter complementary to the decided or not very impure color of any given reflectance will result in a sufficiently slight de-v posit in a corresponding area on the ensuing negative to represent that reflectance in the graduated-monotone area of the print made from that negative.
While usually there remains very little or in many instances none of the'origlnal image detail in the parts colored in the sectional-dyeing area as described above, this does notordinarily preclude photographic effect in the finished color print since either of the two complementary areas may be made the one which is to show complete image detail in monotone (by optional use of the original negative or of a film positive in making the prints on paper) and by other controls described above, and since solid or nearly solid coloring in the sectional dyeing parts is analogous to the obliteration of detail by shadow in ordinary photography. However, when retention of image detail in one or more parts of the sectionaldyeing area is regarded as essential, this may be efiected to an appreciable extent by the use of an acid tannic bath as-a developer in connection with the procedure described above, having the effect of sinking the image to such an extent that it will remain in some degree after the rub-off. In this event, however, it is well that the dye fluid used in such parts contain more of the dye-stuff or be of a very permeating nature since residual image renders dyeing more dimcult and the resulting color somewhat modified by the color of such residual image.
Two and three-color efiects can be obtained in various ways by the application of one and two dyes, respectively, omitting or not omitting the rinsing with warm water after the tannic acid bath, for example, the wash-out area may be, by omitting the rinsing, left either white or only slightly colored, while the dye-application mentioned first above takes well on an area of intermediate density not included in the washout.
Another dye application of a different color can be used also, not taking in this intermediate area but taking if it is desired, in the wash-out area and taking with greater density of color in the area of heaviest-deposit, in subsurface gelatin, and may be brought to complete visibility by a suitable bleach. Also only limited colors by chemical toning may be secured in this heaviest deposit area, for example, that of copper toning after bleaching, even when the warm water rinse has been used.
An alternative method of producing natural colorprints is the production of the two prints carried by transparent support on opposite sides of the same transparent support sheet, in which case, as of course one negative must be appropriately reversed in printing. A still further method is the producing of one print in the usual manner and dyeing the same; applying an additional layer of emulsion over the dyed print, producing a second wash out and dyed print of a second color on top of the first, and repeating the process to secure the third color.
The effects produced may be modified by the nature of the supportfor the emulsion. This support may vary all the way between an absorbent material as blotting paper, which may be caused to absorb much or little 'ofcertain of thedyes, to a wholly non-absorbent support or a support coated with a non-absorbent layer under the emulsion.
There are a variety of ways in which twocolor effects can be produced with one dye in addi-- tion to the two colors effected with auramine as described in the foregoing. By way of illustration, such effects can be produced with an indicator dye, for example Methyl Orange, which can be applied to a storage aged print 50 as to "take throughout but appearing in its acid red color in the image or deposit area and in its orange color in thewash-out area. Also whether or not dye number one is applied in the foregoing dyeing procedure, dye number two can produce a two-color appearance if the aging or tannic acid treatment is so diminished that the dye number two takes also to some extent in the wash-out area, and likewise if a slight amount of dilute sulphuric acid is used in connection with a dye number two not reduced in the presence of sulphuric acid. As to non-dye colors, of course various fixing, and the like.
I have found that it ispossible to dye the "whites or highlight area selectively after having obtained only a swelled gelatin relief, and not. a wash-out relief, and after treating the swelled gelatin relief with the tannic acid bath before the application of the dye, however, the results do not compare favorably with the results with the wash-out.
It is interesting to note that some dyes, such as Magenta, while suitable as a dye number two or dye number three, loses its color in the presence of the hypo and sulphuric acid bleach, the color being revived on the print by a cold water rinse.
Interesting effects can be produced by giving the storage aged print a general exposure to light which nearly or entirely obliterates the visible image before the wash-out procedure is com menced.
It will be seen that the process is capable of multiform manipulative variations, and such variations and modifications may be made within the scope of the following claims without departing from the spirit of the invention.
l. The process of selectively dyeing areas ofa gelatino-chloride print which comprises: producing a wash-out relief from the print; treating said print with a solution of tannic acid; and promptly applying a dye to the thus treated print to take in washed out areas.
2. The process of claim 1 including the steps of treating the wash-out relief with a weak ammonia bath and rinsing before applying the tannic acid solution. V
3. The process of claim 1 which includes the application of the tannic acid to the print still wet from the wash-out step; rinsing the thus solution.
5. The process of selectively dyeing areas of a gelatino-chloride print which comprises: producing a wash-out relief; treating the relief with a solution of tannic acid: applying a dye: drying the print; bleaching the print; applying a dye to take on the bleached areas; and drying the prin 6. The process of claim 5 in which the bleaching is produced by treatment with sulphuric acid and sodium thiosulphate.
"I. The process of claim 5 including the step of soaking the print in dilute sulphuric acid: and applying a dye to take progressively, first on the areas of greatest density.
8. The process of selectively dyeing areas of a wash-out relief print which comprises: treating the print with tannic acid solution; rinsing; bleaching with sulphuric acid and hyp applying a dye reducible with sulphuric acid; moistening with dilute sulphuric acid and applyins a dye to take in the area in which the former dye was reduced.
9. The process of selectively dyeing areas of a gelatino-chloride wash-out relief print which comprises; treating the print with tannic acid solution; applying a dye to take in the washedout areas; and applying further dyes to take in other areas.
10. The process of selectively dyeing areas of a gelatino-chloride wash-out relief print which comprises: applying a gelatine hardener to the wash-out relief print: removing by friction the hardened surface of a chosen area; and applying a dye to take in the rubbed of! area.
11. The process of selectively dyeing areas of comprises: treating the wash-out relief with a solution of tannic acid; removing by friction the surface of a chosen area; and applying a dye to take in the rubbed oi! area. a
12. The process of claim 1 in which the print is taken from a photographic positive.
13. The process of producing a photographic print which comprises: exposing gelatino-chloride coated material under a negative and inducing in the resulting print the eifect of age suilicient to cause gradate'd induration in accordance with the depth of printing of various portions; transforming theprint to a wash-out relief condition; applying tannic acid solution to said wash-out relief; applying a dye having the characteristic of Auramine to yield different colors in silver deposits of diflering depths upon subsequent application of an acid; bleaching the print by application of hypo and an acid; applying a dye; applying sulphuric acid; applying a dye; and drying the finished print.
14. The process of producing a photographic print which comprises: exposing gelatino-chloride coated material under a negative and inducing in the resultant print the eifect of age sufficient to cause gradated induration in accordance with the depth of printing of the various parts: transforming the print to a wash-out relief; applying a solution of tannic acid con-- taining a minor portion of sodium sulphite; applying a dye solution: drying: treating the surface of the coating to give access of dye to lower strata; applyin dye; applying sulphuric acid; applying dye; rinsing and drying.
JOSEPH F. sranmoon, JR.