Volltext Seite (XML)
[NOvEMBER 27,1863. 570 THE PHOTOGRAPHIC NEWS. Proofs upon Paper simply Salted. 0 0-304 Ag which, consequently, 2 Hours. Au 2 — 196 must replace Ag3 = 108 X3= 324. Ag + Au 0-241 0*115 Ag Time of Numerical Exposure. Order. Ag + Au 0 078 [ 0 gr. 034 of gold equi- 0121 Ag 2 Hours. - No. 2. s Portion , toned. ) Ag + Au 0-093 0 0-049 Ag Ag 4- Au 0-040 I 0 002 deficit. [Proofs upon Paper simply Salted. 0-236 Ag 2 Hours. Ag + Au 0-185 0-011 deficit. 0-076 Ag Ag + Au 0-053 0154 2 Hours. Ag + Au 0120 deficit. 0 0 068 Ag No. 12. 1 Portion , toned. ) Ag + Au 0 051 * The American Journal of Photography. Numerical Results. 0-059 0 034 0 092 0-028 Numerical Results. Ag Au 0-028 0 012 0037 0014 Numerical Order. 0-042 0-036 Ag Au Ag Au Ag Au Ag Au Ag Au 0-123 0 062 0 026 0-027 Time of Exposure Ag Au Ag Au No. 3. Portion not toned. No. 15. Portion not toned. 0176 0065 No. 10. Portion toned. No. 11. Portion not toned. No. 16. Portion toned. No. 13. Portion not toned. No. 4. Portion toned. 15 Minutes. 15 Minutes. 15 Minutes. 15 ; Minutes. No. 12. Portion toned. Results of Experi ments. No. 6. Portion toned. No. 5. Portion not toned. No. 8. Portion toned. No.l. Portion not toned. No. 7. Portion not toned. 0 gr. -028 of gold equivalent to 0-046 of silver, the toned portion (No. 10) should contain 0154—0-046=0108 of this metal; but experiment gave 0092 ; in this case, therefore, the pro portion of silver is 0-016 gr. -065 of gold equivalent to 0-109 of silver, the toned portion (No. 14) should contain 0-304—0109=0195 of this metal; but experiment gave 0 -176 ; in this case, then, we find the proportion of silver 0-019 deficit 0 049—0-018 =0-030 of this metal; but experiment has given 0 028; in this case, therefore, we find the proportion of silver Results of Experi ments. 0 gr. 036 of gold equi valent to 0-059 of silver, the toned portion (No. 16) should contain 0 115 = 0 059 of this metal; but experiment gave 0042 ; in this case, then, we find the proportion of silver 0-014 deficit. gr. -014 of gold equivalent to 0 024 of silver, the toned portion (No. 12) should contain 0 068—0 024=0-044 of this metal; but experiment gave 0-037 ; in this case, then, we find the proportion of silver 0'007 deficit. valent to 0-056 of silver, the portion toned (No. 2) should contain 0-121 — 0 056 = 0 065 of this metal; but experi ment gave 0-059 ; in this case we find the proportion of silver 0-006 deficit gr. 012 of gold equivalent to 0-019 of silver, the por tion toned (No. 4) should contain 0 gr. 017 of gold equi valent te 0-044 .of silver, the toned portion (No. 8) should contain0 076 —0-044 =0032 of this metal; but experiment gave 0*026 ; in this case, then, we find the proportion of silver 0-006 deficit. Thus, in all the preceding cases, the substitution of gold for silver has evidently taken place in atomic conditions; this regular progress takes place upon argentic organic matter as well as upon silver, and both before and after toning, and after short as well as after long exposure. Nevertheless, as the con clusions contained in the last column show, experiment in all cases shows a slight deficiency of silver; this deficiency is very evidently due to the acidity of the liquid, to the presence of hydrochloric acid in the toning bath ; this acid attacking (inde pendently of all toning) a portion of the silver, converting it into chloride, which the fixing salt subsequently removes ; this observation explains the well-known maxim ; — acid toning baths redden the proofs. This mode of toning is regular and quick ; it gives slightly red tones, but which are not disagreeable ; but the great danger it presents is shown by the following; it removes more silver than is required by theory, and it diminishes the intensity of the proof in proportions which the photographer has not always the power to check. Moreover, if we compare the experiments Nos. 8, 12, and 16, made after exposure of a quarter of an hour, with the experiments Nos. 6, 10, and 14, made after exposures of two hours, it appears that the deficit of silver is more sensible in the case of short exposure than in long; in a word, it appears that under the dissolving action of the hydrochloric acid the half-tones suffer more than the deep blacks. In conclusion, wo cannot recommend this toning process, as photography is now in possession of a more advantageous one ; still, in cases where it may bo employed, for special works, the operator must print a vigorous proof, in order to compensate for the loss of strength caused by the hydrochloric acid.—Bulletin de la Socidtd de Bhotographie. .0 gr. 062 of gold equi valent to 0-102 of silver the portion toned(No. 6) should contain 0-236 — 0102 = 0 -134 of this metal; but experi- mentgave 0-123; in this case, then, we find the proportion of silver A FEW WORDS IN REGARD TO LIGHTING OPERATING ROOMS FOR PORTRAITURE* Thebe is probably no one department of photographic manipulation so disregarded, neglected, or perhaps as little understood among Americans—in fact, it may be said of all photographers—as the proper lighting of operating rooms; one of the principal causes from which result the great majority of poor, worthless pictures, which we find in every community. This defect in many establishments docs not arise from careless indifference in regard to the character of work pro duced, for nearly all have a desire for success which will remunerate the expenditure of time and capital, aside from the gratification of an honourable pride of reputation, not only with patrons, but in the profession. Many operators, whose knowledge of chemical manipulation is sufficient to enable them to produce passable, or even good work, are so little acquainted with a few simple laws of nature in regard to light, that their productions are almost invariably un worthy the name of pictures. 1st.—TONING WITH ACID CHLORIDE OF GOLD. Toning AFTER Fixing. Proofs upon Paper simply Albumenized. from which we have deduced our conclusions, they have been established in starting upon the fact that in employing chloride of gold, Au’ CP, the latter, in the act of substitution, must theoretically transform it into chloride, and consequently be placed in such a condition that the last fixing may cause the three equivalents of silver to disappear, according to the formula— Au 2 CP + 3 Ag = Au? -f- 3 Ag Cl; No. 0. ] Portion I. not [A toned. J Toning BEFORE Fixing. Proofs upon Paper simply Albumenized.
