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en:protocol_maddox_i

Protocol: Maddox I

Here are the main parameters of the protocol used during Maddox I, by one of three work groups.

General Idea

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.

Formulation

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.

Different tests

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):

  • Test a lesser time for the second maturation, to check the importance of this second maturation.

Concerning the additives:

  • Adding gold in the form of gold chlorosulfocyanide < chlorosulfocyanure aureux> at the end of chemical maturation.
  • Erythrosine B to sensitize to green wavelengths, added at the end of chemical maturation.
  • Cellular extracts of spinach, containing chlorophyl as a sensitizer to red wavelengths, added at the end of chemical maturation.

Tableau à reproduire ⇒ http://www.filmlabs.org/wiki_old/index.php/Protocole_Maddox_I

Preparation of the additives for the tests

**GOLD**

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:

Tableau à reproduire ⇒ http://www.filmlabs.org/wiki_old/index.php/Protocole_Maddox_I

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.

Tableau à reproduire ⇒ http://www.filmlabs.org/wiki_old/index.php/Protocole_Maddox_I

ERYTHROSINE B

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.

CHLOROPHYL

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.

The Different Tests

**Step by Step**

Preparation of the Solutions

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.

The containers:

  • We used jam pots (glass and with covers) or baby food pots (glass and with covers) for the small volume tests.
  • The pot holding solution A must be voluminous enough to house also solution B, which is to be poured into solution A early in the process.
  • We weighed the pots in order to better follow the evolution of weight of the preparation, that way we later know how much to subtract from any weight measurement, and can correctly calculate how much water is lost by evaporation or how much water was absorbed after washing.

The components:

  • We used a 0,01 precise balance to weigh our products, easily found online for less than 10 euros.
  • We use disposable plastic spoons and disposable plastic cups to measure out the products (thus assuring dryness and sterility).

The solutions:

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.

  • For solutions A, the order in which the products were incorporated is the following: Potassium Iodide, Potassium Bromide, and Gelatin.
  • For solutions B, we switched to safelight environment.
  • We continue to add boiling water until reaching 70°C, so that the gelatin of solution A has time to completely melt to give us a homogenous solution.


​​​​​​​Last verifications:

  • Having reached 70°C, we check the temperature of each solution, rinsing with distilled water between each measurement of the different pots to avoid contamination or an uncontrolled start of nucleation.

Precipitation (Emulsification)

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.

Physical Ripening

  • Solution C, containing gelatin, is placed in the bain marie so that it may melt and be incorporated homogeneously at the end of the maturation.
  • For the emulsion, vigorous stirring with the end of the temperature probe must be maintained until the end of this phase, it’s essential!!!
  • Since we don’t have a temperature-controlled bain marie over 55°C and since we have to maintain a constant stirring, we couldn’t keep the temperature of 70°C but the amount of water in the bain marie is enough that it keeps enough heat to be, after 15 minutes, the acceptable temperature of 60°C.
  • At 30 minutes, we’ve reached 50 °C, it’s the end of the maturation, and we add solution C, and take the mix out of the bain-marie.
  • At 40 minutes, we’re ready for the next step. We can consider, though it is not truly quite so linear, that on average we’ve carried out a maturation of 30 minutes at 60°C. Checking the weight of the emulsion reveals a loss of 68g of water through evaporation: the initial total weight being 526g, this means a loss of 13%. We won’t add water to compensate right away but rather after washing, since the washing inflates the emulsion with water.

Chilling

40 minutes after the initialization of maturation, the temperature is below 40°C, we pass to the stage of chilling before washing.

  • The preparation of 420 ml is poured into 3 rectangular s8 containers.
  • Once solid (chilled), they are placed in opaque containers (120 m 16mm metal containers) and placed in a refrigerator at 4°C for 2 hours, the time needed to prepare the following stages, 30 minutes being long enough for chilling to be complete.

Washing

  • The chilled emulsion is cut into small cubes using a disposable plastic knife.
  • They are transferred to a large capacity (5L) bottle, containing water at 4°C.
  • We undertake 6 cycles of washing, each for 1 hour, agitating every 30 minutes.
  • The water used for washing is that of the sink, placed into 5L bottles and chilled in the refrigerator for at least 2-3 hours.

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%.

Chemical Ripening (Digestion)

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.

  • We carried out the digestion at 55°C for the 5 small jars: A, B, C, D and E.
  • We consider that digestion begins after 15 minutes, when the emulsion has melted and reached 55°C. We cover the jars with their tops to avoid all evaporation of such small volumes.
  • From the start, we add 0,35 ml of gold sensitizing solution to pot C.
  • After 30 minutes of digestion, we put away pot A.
  • A t= 55 minutes, we add 0,45 ml of erythrosine sensitizing solution to pot D.
  • At t= 55 minutes, we add 0,45 ml of the chlorophyl solution to pot E.
  • At t= 60 minutes, we take all the jars out of the bain-marie.
  • Jar F is then composed of an equal mix of pots C, D and E.

Coating

  • We used a MiniMadBox to spread the emulsion via submersion on test strips of about 1m.
  • These test stips are recycled from b&w film, bleached with R9 (potassium bichromate and sulfuric acid), then clarified with sodium sulfite (CB2).
  • Each test strip was identified by a code composed of folds and perforations on the ends, according to the different preparation and additives used.
  • The operation requires two manipulators, one person who holds the assembly and the other who holds the test strip by its two ends to maintain a tension and a constant velocity while soaking. To assure a minimum of homogeneity while coating, and thus to hopefully achieve a constant density of the coated emulsion layer, the same person carries out the soaking for each of the bands.
  • We coated the strips when the emulsion of each test was around 32°C.

The strips were suspended and let dry.

Conclusion

  • On obtient un émulsion avec une sensibilité proche de la pellicule de tirage noir et blanc.
  • La sensibilisation à l'or provoque un voile conséquent.
  • On ne peut pas conclure sur une sensibilisation au vert avec l'érythrosine B ni au rouge avec la chlorophylle. Les quantités sont à revoir.
  • Il y a bien un gain de sensibilité avec la durée de la maturation chimique.

Voir aussi

en/protocol_maddox_i.txt · Last modified: 2017/05/02 18:53 by joyce