P R E L I b I I S A R T STUDIES ON DIRECT PHOTOGRAPHIC POSITIT‘ES’ BY G. A. PERLEY ,4ND -%I,.\?i LEIGHTOPU’
During the experiment on solarization phenomena conducted by one of us2 the reversal of the negative photographic image by thiocarbamides was considered. Colonel a’aterhouse3 found that a positive image resulted in place of the normal negative during some experiments made early in July with a n eikonogen developer to which a little phenylthiocarbamide had been added. He obtained more or less complete positive pictures not only with the phenyl compound, but also n.ith allyl-thiocarbamide, Thiocarbamide yielded still less regular results, while urea failed t o give any sort of a reversal The results obtained by Colonel IVaterhouse left much to be desired in clearness. ,After many trials during the first experiments on solarization a more or less satisfactory positive was obtained by adding a small amount of a thiocarbamide to a hydroquinone developer. The work was conducted during the warm summer months. By means of a preliminary immersion of the plates in the thiocarbamide solution, and washing in running water for a short time, fairly consistent positives xere obtained for exposures a little below the normal. Such results seemed to warrant a theory of sensitizing action. As the previous work had not created a really practical method for the production of direct positives, i t seemed advisable to clear u p the weak points. It was evident t h a t a detailed study of conditions mas essential for a clear understanding of the process. A paper read before the Eighth International Congress of Applied Chemistry in New York, September, 1912. Perley: Jour. Phys. Chem., 13, 630 (1909). a n’aterhouse: Proc. Asiatic Soc. of Bengal, Aug., 1890.
G. ,A. Pevley and .Ala?z Leighton
236
At first a developer of the following composition was made : Solution R
Solut1011 A 1,000
I 26 21
grams water grams iYa2S0, (anhyd ) grams hydroquinone
1.000 grams
1 2 6 grami
water Sa,CO, (anhyd )
The thiocarbamide 17 as made according to the method of Reynolds Ammonium thiocyanate was heated in a round-bottom flask a t a temperature of 140' to 180' C for five hours. The remaining thiocyanate was extracted n ith cold Irater. The thiocarbamide was dissolved in hot water, evaporated and recrystallized. X standard solution of I gram of thiocarbamide in one liter of nater Ivas employed. In the early spring n-ork was undertaken to duplicate former results. The developer consisted of 20 cc of the thioand 2 j cc of Solution carbamide solution, 2 5 cc of Solution -4, B X positive of a bron-nish purple color was obtained on plates exposed under a standard lantern-slide plate In many cases only a partial reversal resulted. Much time was expended in varying the different constituents of the developer until a fairly satisfactory positive was obtained. These results are of no importance in the light of our recent work and accordingly may be omitted. Just as the results seemed to be capable of duplication the warm spring days approached. IT-ith this balmy weather some sort of a spring ailment afflicted the developer. Xone of the much prized previous results could be duplicated. The first explanation was that of depreciation of the thiocarbamide solution. The solution of thiocarbamide was titrated from day to day with standard permanganate, and the solution was found to remain quite stable. Sewly prepared solutions failed to eliminate the trouble. I n order to ventilate the dark room properly during the Reynolds: Jour. Chem. Soc.,
22, I
(1869).
Studies on Direct Photographic Positives
23 7
warmer weather it was necessary to open the windows. -It this point it became possible to produce positives of fair quality. The solution of our former troubles became clear. The reactions were exceedingly affected by temperature changes. ; I s the previous data seemed to be worthless in the light of this last fortunate discovery, and as the reactions involved seemed to attain almost a quantitative aspect, a new source of attack was formulated. Every variable involved was placed under quantitative control. Separate standard solutions of each of the constituents of the developer were made, and all other factors were standardized. The 5 X 7 camera employed was made by the Eastman Kodak Co. and equipped v i t h a Cooke anastigmat lens, Series I11 f 6 5, made by Bausch 8r Lomb. X standard photograph was located 19 inches from the lens of the camera and illuminated by means of a CooperHewitt mercury arc lamp \Those center was 2 2 inches above the photograph. A411 photographs were taken n-ith the widest stop if 6 . 5 ) . The following standard solutions were employed : Thiocarbamide, Hydroquinone, Sa,CO, (anhyd ) , Sa,SO, (anhyd ) ,
gram per liter grams per liter I 26 grams per liter I 26 grams per liter I
21
Each of these solutions was measured from a standard burette -4 burette stand was located in the dark room in such a manner that the four burettes were compact, yet easily accessible The water n-as measured by means of a pipette. Considering that the source of illumination and actinic value of the light n-as maintained constant by the above precautions, and that a plate of the same emulsion n-as employed, n-e recognized the following variables : time of exposure, temperature of development, time of development, size of plate, amount of thiocarbamide, hydroquinone, sodium carbonate, sodium sulphite and water. -1 total of
G. A . Perley and Alan Leighton
238
nine variables had to be considered before the perfect conditions could be understood. The plates employed in this work were purchased a t different times, but the Seed 26 X plate was always used. Each one of the constituents was measured into a glass tray and the whole developer was thoroughly mixed before immersing the plate. The developer was used for one experiment and then discarded. Using the concentrations that had previously given the best results the data of Table I were obtained :
TABLEI Size of plate 62/3sq. in. Exposure in seconds, 8. Time of development, j minutes. composition of developer : o 0 2 0 grain thiocarbamide; o 2 7 3 grams hydroquinone, I j 1 2 grams Sa,SO.,. ( 1 j 0 4 gram Na,CO,; 85 grams H,O. ___ ~
No. I 2
3
4
5 6
~
Tetiiperature of developer
Remarks
so c
c I 2 O c 140 c
IO0
16' C 18" C
I
Thin negative Thin negative Best positive Fogged positive Heavy fog Heavy fog
The results of Table I show that only one temperature can be employed for the particular concentration of developer used. The temperature was controlled by inserting the tray of previously cooled developer i n t o a mixture of ice and water maintained a t the desired temperature. h difference of two degrees Centigrade from the best conditions yielded, an absolutely worthless plate. The influence of temperature on this reaction is enormous. This undoubtedly explains the reason for the better success attained previously by a preliminary immersion in running water. During the hot months this served to cool the developer to the essential temperature conditions.
S t u d i e s o n Direct Photographic Positives
239
I n view of these data all future work was conducted a t C during development. The results of Table I1 were obtained by varying the content of thiocarbamide. 12'
T.ki%E 11 Size of plate, f~','~sq. in. Exposure in seconds, 8. Temperature of developer, I 2 O C. Time of development, 5 minutes. Composition of developer : o 2 73 gram hydroquinone Na,SO,; 0.504 gram Ka,CO,; 8 j grams H,O. No.
Gram thiocarbamide
I
o 006
I
j I2
grams
Remarks
Thin negative j Partial positive; high
0
0 010
4 5 6 7
0 0
S
o 024 o 026
9 IO I1 I2
'3 14
lights negative
008
2
3
j Partial positive : high ( lights negative
014
01s
0 020 0 022
o 030 o 032 0 034 o 036 0.040
, 1
Fogged positive Heavy fog Best positive Thin positive Thin positive Thin positive Thin positive Thin positive Thin positive Thin positive No image
It was evident that a t 1 2 O C the best amount of thiocarbamide was 0 . 0 2 grams when used with 85 grams of water, o . 2'73 gram hydroquinone, I . 512 grams Sa,SO,, and 0.504 gram Sa,CO,. This, of course, is not essentially the best developer. This n-ork brought forth a fen- interesting points. Only a very small amount of thiocarbamide (0.003 gram per sq. in. of plate surface) is required to produce a positive. Its action with high concentrations is limited b y the influence it has as a solvent for the emulsion. In other words, a partial positive results with insufficient thiocarbamide ; with a trifle
G. A . Perley and Alan Leighton
2 40
in excess, the reaction is so rapid that a badly fogged plate results; and with still greater amounts, a thin positive with less fog is produced. Above a certain concentration there is only a solvent action. It was interesting to note t h a t for the lower concentrations a fairly dense reddish brown deposit was produced, while just beyond the zone of complete fogging ( 0 . 0 2 gram) a brownish purple deposit made up the positive image. The two colors were absolutely different. The next variable studied was the hydroquinone and the data are given in Table 111.
TABLE111 Size of plate, bL,I3sq. in. Exposure in seconds, S Temperature of developer, I 2 O C. Time of development, j minutes. Composition of developer: 0 0 2 0 gram thiocarbamide, grams Na,SO,; o 504 gram NaLCO,. 8 j grams H?O. No.
Grams hydroquinone
I
512
Remarks ~-
I 2
3 4 5 6 7
0
126
0 184 0 210 0 252 0 0
273 294 336 357
8
0 0
9
9 420
Heavy fog Heavy fog Heavy fog Best positive More dense positive Thin positive Thin positive Partial negative Partial negative
Table I11 s h o w that there is only a comparatively narrow range for the variation of hydroquinone within which good results may be produced. The action may be best understood by a description of the progress of development. In all cases where a more or less good positive results there first appears a very faint negative on the plate. This develops as a rule after one and a half minutes' immersion ; after approximately three minutes, the negative appears to fade into a positive which attains its
Studies on Direct Photographic Positives
241
best contrasts after a total of five minutes’ development. The production is a very thin negative, and seems to be essential to the making of a good positive. The rBle of the hydroquinone would seem to be in the production of just the minimum negative to render a positive. Too small amounts would not yield a negative. Hence, there would be a uniform development over the whole surface. This explains the fog. Too large amounts would yield such a dense negative (provided the exposure was sufficient) that it would injure the positive effect The very thin negative that seemed essential for the success of the positive creates a thin fog in the high lights of the 1-ery best positives The amount of sodium carbonate was next varied and the results are given in Table IT’.
TABLE11Size of plate. 62,’3sq. in Exposure in seconds, 8. Temperature of developer, I 2 C. Time of development, j minutes. Composition of developer : o 0 2 0 gram thiocarbamide o hydroquinone, I j 1 2 grams Sa,SO,, 8 j grams H,O. NO.
I 2
3 4
Grams Na,CO, 0 0 I2tl 0 2j2
6
375 504 o 630
i
0
756
8
0
882
9
I
10 I1
I
I34 386 764
5
-
0 0
I
2j2
gram
Remarks
Blank Very thin negatii e Thin negative Rest positive Fair positive T7ery fair positive (Dense positive, high ) lights negative Dense positive : high 1 lights negati\ e 5 Dense positii-e; high lights
2 negative
Dense partial negatil e Dense partial riegatil-e
Table 11- gave results consistent with Table 111. With increase of carbonate there is of course an increase in the
G. A . Perley and Alan Leighton
2 42
density of the negative produced per unit time. For excessive amounts of carbonate there would then be a negative masking a positive. The data show one interesting point. There is, off hand, no reason why No. z should not have produced the best positive, as the thinnest negative (with no trace of a positive) resulted with this concentration. This result would seem to indicate that a certain amount of carbonate is essential in the production of a positive. The sodium sulphite was next varied and the results are given in Table TT. TABLEV Size of plate, 6?/, sq. in. Exposure in seconds, 8. Temperature of developer, I 2 O C. Time of development, j minutes. Composition of developer : 0 0 2 0 gram thiocarbamide, gram hydroquinone, o 378 gram Na,CO,; 85 grams H,O.
0 2j 2
-~ -
KO.
Grams Xa,SO, ~
I
0
2
0,378
3
0.630
1 5 6
1.008 I . 260 I ,386
3
A
I
j I 2
9
,638 I . 890
IO
2 .j20
I1
2,772
I
Remarks __
Fogged negative
j Partial positive; high lights negative (Partial positive; high ), lights negative Fair positive More dense positive Dense positive Very dense positive Less dense positive Best positive Less dense positive Thin positive
145th increase of sulphite there seems t o be a maximum in the density of the positive. An increase in concentration of sulphite limits the quality of the positive by a seemingly restraining or solvent action. Since the density of the positive passes through a maximum, it is possible to obtain good results with two different concentrations of sulphite ( I ,008 grams and I . 890 grams), yet I . 890 grams is the preferable since there is a minimum of darkening in the high lights. The
Studies on L?irect Photographic Positiz'es
243
data of S o . I show that a certain amount of sulphite is necessary for the production of a positive. The results of Tables I, 11, 111, 11- and 1- indicated that with an exposure of 8 sec., and a development to 1 2 O C, a developer for a plate with 6 ' / , sq. in. of surface area consisting of 0 . 0 2 gram thiocarbamide, 0 . 2 5 2 gram hydroquinone, 0 . 3 7 8 gram sodium carbonate, and I , 8 9 0 grams sodium sulphite in 85 grams of water was the best. &At any rate, consistent results could be obtained. There are a few criticisms on the positive produced, even under the most ideal conditions. First, each plate has a thin light brown fog just beneath its surface. The fog does not appear in the slightest by transmitted light, yet upon reflected light it becomes very evident. This only detracts from the appearance of the plate and not from its use. Secondly, the production of a good positive requires a thin, yet distinct negative. The reduced silver yields in the high lights a very thin fog. while the shadows overmask the negative by the dense positive deposit. The negative is so thin that it does not appear when the plate is used as a lantern slide. Thirdly, the deposits do not have the characteristic black color, but are nearly purple. It is an interesting fact that, after fixing arid washing, the deposit is of a beautiful sepia tone, while after drying i t has a purple hue. Since the attempt to eliminate the negative by variation of carbonate or hydroquinone was a failure, the time of exposure was varied as a last resort. The results as given in Table 17 were obtained. Table 1.1 shows that with too great an exposure the negative develops more rapidly than the positive. For too short exposures there seems to be a uniform surface development. For exposures belon- six seconds there seems to be an insufficient latent image formed to facilitate the development of a contrasting and dense positive. Thus the data of Table VI are consistent with those of Tables I11 and IT7.
G. A . Perley aizd A l a n Leighton
2 44
TABLE1-1 Size of plate, 6'/, sq. in Temperature of developer, I 2 O C. Time of development, 5 minutes. Composition of developer : o 0 2 0 gram thiocarbamide, o 2 5 2 gram hydroquinone; I 890 grams Na2S0,, 0 378 gram Sa,CO,; 8 j grams HZO. Exposure i n seconds
NO.
Remarks ~
I
2
2
3 4 5 6
3 4
-
5
6
-
I
S 9
/
S 9
I 0
10
11
I1
'3
-~
Thinly fogged positiye Thinly fogged positive More dense positive Fair positive Good positix e Best positive Fair positive Fair positive Partial negatix e Searly all negatix-e Segatiye
-ill of the variables had been considered n-ith the exception of the lyater content. Table I gave indications t h a t there might be a possibility of varying the total concentration of the active agent and thereby to alter the rate of reaction. The results of this work are given in Table 1-11. pr.\uI.E 1.11 Size of plate, 6' sq. in. Exposure in seconds, 8 Temperature of de\ elopment, I 2 ' C Time of development, j minutes Composition of del-eloper o 0 2 0 gram thiocarbamide, o 2 j 2 gram hydroquinone, I 890 grams Na,SO,, o 378 gram Xa,CO,. ,vO. ~-
~
~~
I
-7
Grams H,O
~~
5'
68
3
77
4 5 6
81
-
i
Rem a r k s
85
81 5 9' IO1
Thin negative Thin negative Thin negative Fair positive Best positke Thinner positive Heavily fogged positive F'og
S t u d i e s o n D ii.ect Plaotogiaph ic Positives
245
Table 1-11 shows that only within a narrow range of total concentration can any sort of a positive result. With a high concentration the latent image is developed the more rapidly and the thiocarbamide exerts a solvent action. With greater dilution, the rate of development of the whole surface becomes uniform with the resultant formation of a fog. In order to obtain a qualitative idea concerning the effect of plate surface on the process, an exposed plate of the normal size was developed under the best conditions second exposed plate was immersed in the same developer -1very badly fogged positive resulted. It thus seemed essential to express the concentration of the developer in plate surface units Table 171 indicated a method of applying the process a t room temperature and accordingly the results of Table T'III viere obtained. TABLE1-111 Size of plate, 6-' sq in. I:\poiure in seconds, 6 Temperature of developer. I S o . Time of development 5 minutes. Composition of deyeloper o 0 2 0 gram thiocarbamide , o 2 5 2 gram hydroquinone I 890 gram5 Sa,SO,, o 378 Xram Sa,C( ) ? ~
so.
Grams H,O
I
-1-1
2
51
3
1
61
Kettiarks
17ery thin positi\-e €%estpositive Dense and fogged positive Fog
The work shon-ed that it is possible to obtain a positive a t room temperature, yet the water content must be regulated with great care. Curing the n-ork a t I 2 O C a universal thin haze seemed to appear on all of the plates with the exception of one box. One box of the Seed 26 X plates gave a very sharp contrasting positil-e. A t the time, this was considered purely a manipulative error. *At 18' C this haze increased slightly in density. id
246
G . A . Perley and Alan Leighton
In order to check up the influence of the emulsion on our results a 3l 'J x 4 lantern slide plate made by the Imperial Dry Plate Co. was exposed under the same conditions as in the previous work. The developer consisted of o 0030 gram thiocarbamide, o 038 j gram hydroquinone, o 2 9 0 j gram Sa,SO,, o 0 7 7 5 gram Sa,CO, and j 8461 grams H,O per square inch of plate surface An exceedingly fine positive resulted, yet with the characteristic minor faults With a Seed 26 X plate of the same size and developed under the same conditions the thin fog was visible. Thus, much depends on the emulsion when perfect results are sought. This work must be considered as a preliminary study of the process -411 indications point to the possibility of producing a direct positive of fine quality. Experiments are already proceeding with a view t o substituting such developing agents as pyrogallol, eikonogen, metol, glycine, pyrocatechin, amidol, rodinal, etc , for the hydroquinone. The results, to date, indicate that the reducing agent affects the color of the resulting deposit. Eikonogen was found to yield far less fog, no visible negative after fixing, and almost a black deposit. The results on this are very incomplete. There is also the possibility of substituting allyl thiocarbamide, phenyl thiocarbamide, and, in fact, all of the thiocarbamides in place of straight thiocarbamide. The results will be greatly different from our present series. -4 small amount of work on the allyl thiocarbamide has shown possibilities. In place of the purple deposit consistently obtained by use of thiocarbamide, a most beautiful red deposit results. If it were not for the reddish fog, the present results would yield a plate almost unequalled by hand painting for use as a transparency. The results on this are incomplete. A later paper on the theory of this process will attempt to clear the problem. Instead of using some thiocarbamide or derivative it should be possible to find some substance that will eliminate the present unpleasant fog. Other possible sources of attack are in the addition of
Studies on Direct Photographic Positives
247
some type of a restrainer which will restrain thenegativeand leave the positive unaffected. B small amount of potassium bromide was found to restrain the positive more rapidly than the negative. A4syet some chloride, citric acid, etc., have not been tried as restrainers. If the present thin negative and brownish fog formation can be restrained, a perfect plate may be produced a t room temperatutre. The work is still under investigation. To summarize : I . The work was attempted in order to produce consistently direct positives of good quality. 2 . The production of a positive by the Waterhouse process is most easily influenced by alteration of the conditions governing the reaction. 3. The variables considered in this preliminary study were : time of exposure, temperature of development, time of development, size of plate, amount of thiocarbamide, amount of hydroquinone, amount of sodium carbonate, amount of sodium sulphite and amount of water. Under the conditions the same emulsion was employed and the source of illumination and actinic value of the light was maintained constant. 4.The temperature during development must be carefully regulated. Utilizing a given concentration, the temperature cannot be varied more than one degree centigrade. j . The quantity of the developer utilized governs the resultant positive I t is best expressed in plate surface units. 6. By exposing a plate in a camera to an object illuminated by a Cooper-Hewitt mercury arc light a t a given distance, a positive was obtained after j minutes’ development in the following solution maintained a t I 2 O C : o 0030 gram thiocarbamide, 0 . 0 3 7 8 gram hydroquinone, o 2837 gram Xa2S0,, o 0j67 gram Na2C0, and 1 2 7627 grams water per square inch of plate surface. 7 . An excess of any constituent which favors an increase in the development of the latent image yields a partial nega-
248
G. A . Perley and i l l a n Leighton
tive (or a masked positive). ,In insufficient amount produces uniform development and a resultant fog. 8. An excess of thiocarbamide acts as a solvent for the emulsion. An insufficiency does not visibly affect the thin negative resulting from normal development. 9. Xo single constituent can be omitted from the above developer to obtain good results. I O . At 1 2 ' C a small quantity of water (high concentration) causes the thiocarbamide to exert its solvent action. ,4 large quantity of water ilow concentration) retards the development of the latent image u-ith the production of a fog. 11. Under the same conditions as in 6, a t 18' C, an exceedingly good positive can be obtained on a lantern slide plate with o 0030 gram thiocarbamide, o 038; gram hydroquinone, o 2907 gram Sa?SO,, o 075 gram Sa,CO, and 7 8461 grams n-ater per square inch of plate surface. 1 2 IT'ork is being conducted on the substitution of eikonogen, metol, pyrogallol, amidol, glycine, rodinal, pyrocatechin, etc , for hydroquinone ,Allyl thiocarbamide produces red deposits, while thiocarbamide yields bluish tones The derivatives are under investigation. 13. ,1suitable restrainer for the yellon- fog and thin negative would yield great improvements. 14. The contrast and clearness of the final deposit depend much upon the emulsion on the plate. I j . The only sources of dissatisfaction with the present positive a r e : first, the bluish color of the deposit; secondly, the necessity of a preliminary appearance of a thin negative; thirdly, the appearance by reflected light of a yellowish fog. S e k Hantpshzre College
Durham. S H .
