Change in the Molecular Weight Distribution of Gelatin by a High Pressure Slurry Jet

Abstract

Physical and photographic properties of gelatin depend on the molecular weight distribution of the gelatin, which it is important to control. We controlled the molecular weight distribution of gelatin by pressurizing the sample gelatin solution and jetting it at high velocity from a nozzle to a collision plate. II was found that this method teas effective in controlling the molecular weight distribution of gelatin and in preparing a gelatin which contains mainly ± and β components and few high and low molecular weight components.     

D-Amino Acids in Non-gelling Components of Gelatin

Abstract

As a possible cause of the non-gelling property of the sol fraction of gelatin, we considered that higher D-amino acid content should result in decreased formation of helices. The sol fractions ivere extracted from gelatin gels and hydrolyzed to amino acid mixtures. The rates of reaction with D-amino acid oxidase (D-AOX) were recorded for thehydrolyzates. For a comparison, residual gels were also treated similarly. The sol fractions always gave higher results than the residual gels for the three types of gelatin examined. The result also showed that the rates obtained from the sol fractions were in the order: limed ossein > limed hide > acid pigskin.

To examine the reliability of this procedure the D-form content for each amino acid in the sol from the limed hide gelatin was compared with that of the residual gel. The contents in the sol were higher than those in the residue for most of the amino acids which racemized. The results indicate that the increased racemization of amino acids on the extraction of gelatin from raw materials is a cause of the non-gelling property.     

The Influence of Pre-treatment on the Properties of Photographic Gelatin

Abstract

The influence of the liming period in the manufacturing process on the chemical and photographic properties of gelatin was investigated. Three limed osseins soaked for various periods were prepared and gelatins zvere extracted from them. The impurity contents of the gelatins and the physical restraining properties decreased with prolonging liming periods. The impurity contents and physical retardance were also relative to the extraction order. The deionization treatment of gelatin decreased the impurity contents and the differences of restraining effect with extraction order. Furthermore, the fractionation of sample gelatins by use of gel permeation chromatography was applied to study the relationship to the molecular weight of impurity contents and amino acid composition, as affected by the liming period.     

Measurement of Methionine and Methionine Sulphoxide in Photographic Gelatin using HPLC

Abstract

This report describes an improved method for the direct and simultaneous measurement of methionine and methionine sulphoxide in photographic gelatin using HPLC in the cationic exchange mode. While researchers have reported initial results using p-toluenesulphonic acid as the hydrolysing agent, this work shows significant improvements in both accuracy and precision using a melhane-sulphonic acid hydrolysis of gelatin. This report is a current assessment of this analytical method. Method evaluation including linearity, accuracy, and precision data are presented.     

Degradation of Gelatin in Historical Photographs

Abstract

In order to study age related changes in photographic gelatin toe analysed black-and-white roll film before and after accelerated ageing and samples of naturally aged glass plate negatives. Two-dimensional gel electrophoresis (2D-PACE) was used to separate collagen chains In the gelatin by isoelectric point (pi) and molecular weight. The results shoiv that the x-chatns break down into smaller fragments on ageing. Amino acid analysis ivas performed to examine the oxidative deterioration of gelatin. It shows that the amount of lysine decreases with age.     

How to Orient Collagen and Gelatin

Abstract

The arrangement of triple helical domains of gelatin molecules may have important physical consequences in photographic gelatins. We review work which indicates that lyotropic liquid crystallization is important in defining molecular orientation and packing in collagens and suggest that it would be worth looking for similar effects in gelatins under certain conditions. We present a preliminary observation which suggests that gelatin can actually behave as a liquid crystal. The possible role of lyotropic liquid crystallization in photographic manufacturing and the interaction of gelatin with other photographic components, such as silver halide, needs further investigation.     

The Estimation of Restrainers

A quantitative method is described for the chromatographic separation and subsequent polarographic estimation of adenine in gelatin. The method, which has been applied to about 200 gelatins, has two important features. It is specific for adenine and enables a visual assessment of other purines and pyrimidines to be mode in the course of the procedure.

Hide gelatins have adenine contents from 10 200 ppm., but the large majority are from SO 50 ppm., ossein gelatin contains from 4–6 ppm., and pigskin between 30 and 50 ppm.     

Electroless deposition catalysed by gold in the photographic gelatin layer studied with positron annihilation

Abstract

The effects of free volume holes in the photographic gelatin in the electroless deposition process was studied by positron annihilation technology in this paper. The results show that, after complete activation, the average volume of the free volume holes in photographic gelatin decreased by about 0.011 nm³ which is equivalent to the volume of a gold atom. On an average basis, every free volume hole was filled by a gold atom which catalysed the electroless copper deposition. The copper grain formed in the electroless copper deposition was not filamentary in shape but a spherical stack. After electroless copper deposition was completed, the average volume of the free volume holes in the photographic gelatin decreased by about 0.020 nm³ which is equivalent to the volume of three copper atoms. Therefore, the deposition of copper in isotropic and spherical form was not hindered by free volume holes in photographic gelatin.     

The Effect of Deformation on Solarization

Several non-aldehydic components of gelatin (nucleic acids, oses, poly-oses, ...) simulate the action of aldehydes with the two reagents (thiobarbituric acid and 3-methyl-2-benzothiazolone hydrazone) used to determine aldehydes in photographic gelatin. Their interferences are always important and the analyses artificially group under an unadapted name aldehydes (if they actually exist in gelatin) and compounds of various compositions.

Under these conditions “aldehyde determinations” in photographic gelatin are rather control operalion than actual analyses.     

Silver Halide (Sensitized) Gelatin in Agfa-Gevaert Plates: The Optimized Procedure

Abstract

Silver halide sensitized gelatin (SHSG) is one of the most promising techniques for the fabrication of transmission holographic optical elements, achieving relatively high sensitivity of photographic material with the low scattering and high light stability of dichromated gelatin. In this paper we present the optimized procedure in Agfa-Gevaert plates. Diffraction gratings with a diffraction efficiency up to 80% and a noise level of less than 1% are obtained with a sensitivity 10³ times better than dichromated gelatin.     

Effects of N02 and S02 on the Degradation of Photographic Gelatin

Abstract

The degradation of photographic gelatin exposed to a mixture of two pollutant j gases, NO₂ and SO₂, was investigated by swelling measurements and steric I exclusion high performance liquid chromatography. The study, performed on one unhardened gelatin and two hardened gelatins, showed that all three are sensitive to pollutants. Two major effects were noted: the first was an increasing of the swelling of the gelatin films in deinineralized water and the second effect was a change in the steric exclusion chromatographic profile, corresponding to a shift to smaller molecular weights. Both these phenomena indicate that the pollutant gases induce hydrolysis of the gelatin macromolecules. Nevertheless, for the same exposure, the hardened gelatins are shoum to be less degraded than the unhardened one. Thus, even if it does not protect the photographic gelatin totally from attack by the pollutant gases, hardening slozos down its deterioration.     

Interactions in Caseinate/Gelatin Systems

Abstract

Interactions in mixtures of gelatin and sodium casemate have been studied over a range of pH. Phase separation in these mixtures has been examined using electrophoresis to identify protein components involved in complex formation. Rheological properties and functional properties of compatible mixtures have been evaluated. Mixtures of 1 % acid-processed gelatin and 1 % caseinatc were found to interact at pH 5.5 to form a separate complex coacervale phase. At lower pH levels, the caseinate component formed aggregates but did not precipitate in the presence of gelatin. These complex systems had increased gel strength compared with gelatin alone and produced low-melting gels of reduced elasticity. Further synergistic increases in gel strength were observed in the presence of 10% maltodextrin..     

Active Impurities in Photographic Gelatins

The problem of correlation between active impurities content of inert photographic gelatins and their effect on crystal growth and chemical sensitization is discussed.

Good correlation has been found between the restraining properties as evaluated by some turbidimetric tests (Reindorp and AmmannBrass) and nucleic acid impurities and proteic sulphur compounds as detected by the Abribat test. Some tests give better correlations than others and a new modification of the Abribat test is proposed.

It is shown that when the inert gelatins are tested with a direct positive emulsion there is a linear relationship with high correlation coefficient between speed and proteic sulphur content.     

Some Improvements to the Manufacturing Technology for Skin Photo-Gelatin

Three new concepts are proposed producing skin photo-gelatin. 1) The yield of gelatin from the traditional metlurd ot production is too low. It can be increased greatly if the technology is suitably improved. 2) To obtain a product with a high quality the old. three main elements at extraction hatv been reviewed and three new elements for pre-treatment, and three new elements for extraction haiv been applied, in all six main elements. 3) The energy consumption should be dependent on the necessity to guarantee the quality.

Obviously these three new concepts can also be applied to ossein gelatin.     

Adsorption of Gelatin and Sodium Dodecyl Sulphate to Polystyrene

Abstract

Neutron reflection experiments have been conducted on the adsorption of gelatin to polystyrene, and the effect of sodium dodecyl sulphate (SDS) on the adsorbed layer. The substrate for adsorption zvas a silicon crystal spun-coated with a film of polystyrene. This xvas placed in contact with different concentrations of gelatin solution betuven 0.00017% and 0.5% by weight, and reflectivity profiles obtained at 35 °C.

Rinsing the gelatin layer with ivatcr was found to remove some material from the surface of the layer, but not significantly change the composition. The addition of SDS solutions decreased both the thickness and composition of the gelatin layer. The most applicable model for the combined system was found to be gelatin and SDS combined in a single layer with exponential profile.     

The Role and the Effect of Calcium Ion Content of Photographic Gelatins on Coating Defects

The influence of the calcium ion content of some photographic gelatins on the adhesion of gelatin solutions to emulsion layers was investigated by surface tension, pH and viscosity measurements and by coating using the dip method.

Adhesion of the gelatin layers was examined in the coating process under the following conditions:

Surface tension at varying wetting agent concentrations, for gelatin solutions which contain calcium ions from 0 to 5760 ppm concentration.

Surface tension at varying gelatin concentrations.

Surface tension at varying pH values of the gelatin solutions used in the coating process.

The experimental results demonstrate that, at gelatin concentrations between 2 and 4%, the adhesion ability of a gelatin solution on a dry or wet gelatin (emulsion) layer depends on the Ca2* content of the coating solution. It is necessary to have at least 1000 ppm Ca2* concentration to guarantee a perfect adhesion and a perfect coating. Gelatin source, pH and the viscosity of the system are unimportant.     

Plate and Frame Filtration in Photographic Gelatin Manufacturing—Some Practical Considerations

Abstract

Gelatin filtration is a required operation in all photographic gelatin manufacturing facilities. For lime-processed bovine bone gelatin, many different filtration methods can be used, one of which is plate and frame filtration. The successful operation of plate and frame equipment depends on a good working knowledge of, and careful adherence to, good filtration practices. Careful choice of a filter medium is also important. This paper outlines many of the practical considerations gelatin manufacturers should think about when setting-up and operating plate and frame equipment, and choosing filter media.     

The Flash Photolysis of Dyes Adsorbed to Emulsion Grains

A technique has been developed for the flash-photolytic study of sensitizing dyes adsorbed to photographic emulsion grains, utilizing the optical properties. of very fine silver halide grains in conventional gelatin coatings. Flash-induced transient absorptions were readily observed with four cyanme dyes, so demonstrating the effectiveness of the techinque for dye-sensitization studies. The transients were shown to decay by two first-order processes and were attributed to the dyes m their adsorbed state.

The absorption spectra of the adsorbed dyes are also presented.     

Impact of Calcium and Methionine on the Variability of a Sulphur and Gold Sensitization on a Bromoiodide Emulsion

Abstract

Chemical sensitization uniformity requires tight batch-to-batch control of components of gelatin as well as the non-gelatin components that are present. Chemical sensitization sensitivity to variations in methionine and calcium was examined using a bromoiodide emulsion at fixed levels of sulphur and gold sensitizer. Hydrogen peroxide treatment of gelatin was used to generate a series of partially oxidized gelatins with varying methionine content. Calcium variation was examined by choosing gelatin with known natural variations in calcium and by addition of calcium salts to deionized gelatins. Sensitometric changes were seen as a function of both calcium and methionine variation. Results indicate that methionine and calcium must be carefully controlled to minimize photographic change.     

Impact of Non-gelatin Components Present in Gelatin on Sulphur-plus-Gold Chemical Sensitization of a 3-D Polydispersed Emulsion

Non-gelatin components present in gelatin can have a significant impact on chemical sensitization despite their low concentrations. A limed bovine ossein gelatin was spiked with various inorganic ions and non-gelatin proteins that contained cysteine and cystine. These gelatins were used to compare sensitization sensitivity to varia-tion in gelatin chemistry with that of bromide (pAg) variation. Chemical sensitization was carried out at fixed levels of sulphur and gold sensitizers. Variation in gelatin chemistry altered sensitometric performance of the emulsion similarly to small variations in pAg. Control of non-gelatin chemistry is desirable to minimize photographic change.