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Here are the main parameters of the protocol used during Maddox I, by one of three work groups.
For Maddox I, we wanted to obtain an emulsion with the necessary sensibility to film, for cinema. We took up the formulation exercise of adapting an industrial formulation to simple, artisanal conditions in a new process. The modifications are imagined according to variations in the indications used in industry to describe the composition of an emulsion.
To start we modified the emulsion-making process referenced in the 4th edition work by Paul Glafkidès, “Physique et chimie photographique”, to then prepare several small quantities of emulsions in parallel to test different variations. To understand the results, several tests will be read by a densitogram.
Below you’ll find, not a tutorial, but a report of the results of an experiment.
We prepare a so-called ‘neutral’ emulsion (see type of emulsion): the basic formulation of all of our emulsions contains potassium bromide (KBr), potassium iodide (KI) and silver nitrate (AgNO3), gelatin, and water.
Tableau à reproduire ⇒ http://www.filmlabs.org/wiki_old/index.php/Protocole_Maddox_I
/*Base, formule décrite dans “Physique et chimie photographique” édition 4, de Pierre Glafkidès.
On a quest for an emulsion sensitive enough to film outside without a strong summer sun, the tests revolve around two axes: additives and the way of executing the preparation (the process). We have to agree upon an experimental protocol and have a plan for each experiment in order to run parallel tests over the course of three days.
Concerning execution of the preparation (the process):
Concerning the additives:
The addition of gold to the surface of the crystals largely increases the sensibility of the emulsion by creating an efficient sensitive center via gold sulfur. To do this, the emulsion must undergo a chemical maturation and the gold must be introduced by l'aurothiocyanate (sulfocyanure aureux). The sulfur existant in the gelatin is indispensable in the emulsion though it may also cause fogging in the form of a metallic gold deposit. Thus the nature of the gelatin has a determining role in the success of this method of sensitization, but the size of the crystals formed in the first maturation also plays a role.
In the future, a serious test could be imagined, in which the optimal quantity of additional sulfur could be determined. For Maddox I, we carry out a sort of a blind test, guided nonetheless by the process outlined in Glafkidès’ “chimie et physique photographique”. However, we don’t have the same products and the chloric acid is already in solution.
Chloric acid (tetra-chloric (III) acid 3-hydrate) is often sold as gold chloride. The exact name should be verified in the security sheet accompanying the product, since gold chloride also exists but is not the acid which we need.
L'acide chloroaurique (Acide Tétrachloroaurique(III) 3-hydrate ) est souvent
The original formula and our modifications are presented in the following table:
The solution thus prepared contains 0,5 mg gold/ml. Glafkides provides an example describing the use of this solution. Using a cross product, we can determine the quantity we should incorporate at the end of the chemical maturation. We could also incorporate it at the beginning of maturation, which is more efficient (economical, easier?). However, since we want to divide the emulsion for separate tests later, we add them a little before the end of the chemical maturation to assure as much homogeneity of conditions as possible, allowing for a more trustworthy comparison.
L'érythrosine B is a sensitizer to green light. Its inclusion renders the emulsion orthochromatic.
Disactis has a 0,3% solution in stock. As indicated on the bottle, we will add 1,5ml for a preparation of 100ml of emulsion at the end of the chemical maturation.
Older literature alludes to the chromatisation of emulsion using chlorophyl, which sensitizes to red. We want to procure some chlorophyl by extracting it from spinach leaves. However, if we want to purify it by column chromatography we need to use an eluent: a mix of petroleum ether and diethyl ether. Two products which we had not anticipated in our preparative orders.
So, we’re going to simply smash the leaves, recuperate the green juice, and dilute it 50% in ethanol. Alcohol will allow the cells and the chloroplasts within which contain the chlorophyll to dissolve, as well as other photosynthetic pigments such as xanthophyll or carotenoid. Though the addition of the last two pigments may be helpful, we worry that the other molecules and cellular debris that we cannot fully filter (using simple sedimentation) may cause a problem.
This session, Maddox I, is carried out with the equipment and in the space of the Abominable Lab in Paris.
To begin we prepare a single emulsion which will be divided at the start of chemical maturation. Its volume is 420 ml. 150 ml will be used for tests (5x30ml), and the rest will be used later to test the MadBox.
We used a non-regulated bain-marie to bring the solutions to the desired temperature, regularly adding boiling water from an electric water boiler. The temperature control is thus done via thermometer readings in the pot containing the greatest volume of products (solution B of preparation A) . Our thermometer has a probe at the end of a wire which can be used as a stirrer.
Once above 50°C, we added the products to be dissolved according to the formulation described above.
When we reached 70°C, we used a pipette to add solution B to solution A over the course of 10 minutes, stirring vigorously in the pot A. The addition was done in two parts: we added the first half of solution B in two minutes, and the second half spread over the last 5 minutes.
40 minutes after the initialization of maturation, the temperature is below 40°C, we pass to the stage of chilling before washing.
At the end of washing, after draining, the weight is measured: an excess of 37 g of water were absorbed by the gelatin, i.e. 7%.
In order to prepare 16mm test strips for the different emulsion tests, we need to use 30ml per test. If there are less than 20mm in the baby food jar, the MiniMadBox doesn't reach far enough for the film to soak in the emulsion.
We take a sample of 38g for each of the 5 pots (A,B,C,D,E). Test F will be a mix of pots C+D+E. The rest will be put back into the refrigerator and matured using the best parameters, in some future day when the Abominable team will want to test their MadBox currently under construction.
The strips were suspended and let dry.
▪ Fabrication artisanale
▪ Émulsion photosensible
▪ Conseils pratiques
▪ Protocole Maddox III
▪ Voiler l'émulsion