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Teaching Holography in Classrooms

Making Holograms with PFG-03M Plates with JD-4

 

By T. H. Jeong, Riley Aumiller, Raymond Ro, (Lake Forest College)

and Jeff Blythe (University of Cambridge)

Edited by Alec Jeong

Copyright © 2003-2005

 

ABSTRACT

This paper is useful for teaching holography workshops in classrooms as well as in makeshift locations such as museums, businesses, and homes. The target audience is very general, young children to adults of any profession, all of whom have no prior experience in making holograms.  A typical number of participants is twenty-five, but can vary depending on space and personnel availability.

A central original contribution of this paper is the discovery of a new chemical processing regime for the Slavich PFG-03M holographic plates using what is now called the JD-4 developer kit.  These silver halide plates have the highest resolution of its kind and some of the world’s best holograms have been recorded on it for several decades.  Due to its low sensitivity and long developing time (12-15 minutes if using GP-2 developer, accompanied by natural drying), this material has historically been excluded from use in workshops. 

Our new processing regime JARB (first letters of the authors’ last names) has makes PFG-03M possible for classroom use. JARB has the following advantages: It (1) increases the sensitivity of PFG-03M emulsion ten-fold without sacrificing resolution; (2) hardens the emulsion during processing without significant shrinkage; (3) has a ten- to twenty-second development time; (4) is quick drying using squeegee and warm air; and (5) allows the finished hologram to be viewable with laser or incandescent light.  Other advantages of JARB are (1) low toxicity, (2) low volatility, (3) non-staining, (4) low cost, and (5) long shelf life.

Keywords: holography, beginner holography, teaching holography, silver-halide processing, PFG-03M, JD-4

 

1.  INTRODUCTION

 

It has been well recognized that holography is a valuable subject for introducing young students to all the major topics of modern optics.  These topics include light propagation, interference, diffraction, polarization, scattering, and photochemistry. Some of the major problems that prevent greater acceptance of holography  in middle and high schools include expense, laser and chemical safety, lack of darkroom facilities, and time limitations in class and laboratory periods.

 

Thee above problems are addressed in another article by the same authors entitled "Simple Holography".  In this current article, we will see that PFG-03M with JD-4 developer (JARB) further minimizes these pracitical limitations.

PFG-03M has been used in Russia and elsewhere for making the highest quality exhibition holograms for several decades.  One can simply develop such plates in one step using the GP-2 formula. However, this combination is not suitable for school use because of the following factors: (1) the sensitivity of PFG-03M is 1.5 millijoules per square centimeter (mJ/cm2); (2) the development time is 12 - 15 minutes; and (3) the holograms must be dried naturally by evaporation, which may require one hour or longer depending on the humidity.

These problems prevent schools from using PFG-03M with GP-2 because (1) the low sensitivity means lasers with greater outputs are needed, presenting an eye safety dilemma; (2) longer exposure time is required, presenting a mechanical stability problem; and (3) the time required for the hologram to dry exceeds the duration of a class or laboratory period.

The application of JARB on PFG-03M resolves all of these problems.

 

2.  APPLICATION OF JARB (JD-4) ON PFG-03M

The discovery of using JARB for quick processing of holograms recorded on Slavich PFG-03M plates and film was made by Tung H. Jeong, Riley Aumiller, Raymond Ro, and Jeff Blyth; thus it is called the JARB processing regime.  Commercially, the chemical developer used is now called called JD-4.

JARB is ideal for making holograms during a lecture demonstration, or for laboratory exercises or workshops where many students must make holograms in a limited time. The advantage of JARB is that it effectively increases the sensitivity of PFG-03M ten times, from 1.50 to 0.15 millijoues/cm2.  Thus the exposure time for holograms is one-tenth as long as when processed in GP-2. The typical development time is 20 seconds. Finally, drying time is drastically reduced by using warm air (from a hair dryer) because the JARB development hardens the emulsion.  The total processing time using JARB can be as short as three minutes, from developing to drying!

The composition of JARB is a modified version  of what was originally intended for processing “BB” plates  manufactured in Germany (Birenheide, R., “The BB Emulsion Series: Current Standings and Future Developments”, SPIE Volume 3358: 28-30 (1997), ed.Jeong). It is mixed using three glass (or plastic) containers marked “A,” “B,” and “Bleach”, each with 1 liter of distilled or de-ionized water. Exercise extreme caution in labeling the bottles and keeping them out of the reach of children to prevent accidental ingestion of the contents).

 

Chemicals

Commercially, the chemical developer used is now called called JD-4, and contains the following.

Developer Part A--makes 1 liter solution

  • Metol or Elon (p-Methylaminophenol sulfate)-- 4g

  • Ascorbic acid powder -- 25g

Developer Part B-- 1 liter

  • Sodium carbonate, anhydrous--70g

  • Sodium hydroxide-- 5g

Bleach-- 1 liter

  • Copper sulfate (pentahydrate)-- 35g

  • Potassium bromide-- 100g

  • Sodium hydrogen sulfate crystals-- 5g

                                                                                                                     

Mixing instructions

  1. Use three l liter (or larger)size clean glass or plastic bottles with leak proof caps.  Label them A, B, and Bleach respectively.

  2. Warm the distilled or de-ionized water to about 40o C (warm to the touch). 

  3. Fill the bottle marked A with 700 ml of warm water.  Dissolve the Metol in it, then add the ascorbic acid.  Add 300 ml of warm water to make 1 liter of Part A developer. Tightly cap the bottle. Part A will oxidized if it is exposed to oxygen.  In time (over a few days to few weeks), the solution may turn yellow due to the oxidation of ascorbic acid; the solution is still useable.  Once the solution turns dark brown,  the potency is lost and should be disposed. 

  4. One way of protecting it from oxidation is to subdivide the solution into smaller bottles so that the unused portions are in fully capped bottles, with little or no air space on top.  Refrigeration also slows down oxidation (exercise extreme caution to prevent its mistaken identity as food).

  5. Follow the same procedure for Part B (add the sodium carbonate and sodium hydroxide in either order).  This solution will keep for many weeks.

  6. Follow the same procedure for mixing the Bleach. This solution has very long shelf life.

 

Hologram exposure,

For detailed instructions on making reflection and transmission holograms, see the article "Simple Holography" on this website. 

Using PFG-03M film or plate, expose the hologram so that each square centimeter area receives 0.15 to 0.4 millijoules of energy (there is batch-to-batch variation).  For example, if a 5 milliwatt diode laser without a lens is location 40 cm from the plate, the exposure time is approximately 5 to 7 seconds.

Preparation before processing:

Have the following items on hand:

  • JD-4 parts A, B, and Bleach

  • 1 gallon (4 liters) of distilled or de-ionized water

  • 2 small glass or plastic trays, just large enough so that the hologram you are making can be submerged in a horizontal position.  Disposable weighing dishes are recommended. For processing 2.5x2.5 inch plates, we recommend buying dishes from Cole-Parmer Instrument Company (), catalog number U-01018-14 hexagonal weigh dishes, 4 3/4" dia. x 7/8" dia.

  • 2 large glass or plastic trays to hold 1 liter of distilled water for rinsing

  • 1 large tray to hold 1 liter of distilled water mixed with about 1 cc of photographic wetting agent, such as Photoflo (optional, but recommended).

  • 1 rubber glove

  • Label one small tray as developer.  Mix equal parts of A and B so that the hologram to be developed can be totally submerged

  • Next to the developer tray, place a tray with 1 liter of distilled water

  • Next, label another small tray as bleach.  Put enough bleach into it so that the hologram can be totally submerged

  • Next to the bleach, place another tray with 1 liter of distilled water

  • Finally, place the tray with the wetting solution in 1 liter of distilled water

Let's review for a moment. So, we now have our "assembly line" of trays placed in the following order: developer, rinse, bleach, rinse, wetting agent. To view the finished holograms, we recommend an incandescent spot light. A good and inexpensive light is a Phillip 45 Watt “narrow spot” flood light that operates on 110 volts and sold in hardware stores. The best lamp is ESX(20MR16) run on a HATVS12-60WD transformer sold by lighting companies.

Processing procedure:

After the holographic plate is exposed, hold it by the edges with your gloved hand, with the emulsion side (sticky side) facing upward.

  1. Development:  Quickly submerge the plate into the developer so that all parts get wet evenly.  Agitate it for about 10 to 20 seconds. The hologram should turn black (at least a density of 2, i.e. about 1% light is transmitted).

  2. Rinse: Rinse the developed hologram in distilled water with agitation for about 20 seconds.

  3. Bleaching: Place the rinsed hologram into the bleaching solution; agitate it until the plate is completely clear (this may take up to 1 minute); bleach for another 10 seconds.

  4. Rinse.  Rinse the bleached hologram in distilled water with agitation for about 20 seconds.

  5. Wetting agent:  Place the finished hologram in this solution for about 20 seconds.

The hologram is finished except for drying.  The best way to dry the hologram is to stand it against a vertical surface with the bottom edge resting on a hand-towel or tissue paper. Best results are obtained when it dries naturally in clean air. However, if time is limited, the hologram can be quick-dried by holding it vertically and blow warm air across it with a hair dryer.  For a reflection hologram, the image can be viewed, after thorough drying,  using the laser light that exposed it or an incandescent spotlight.

 

3.  PRACTICAL CONSIDERATIONS FOR WORKSHOPS

In this section, we will present practical ways of setting up and operating workshops in makeshift locations using commonly available equipment.

“Darkroom” preparation and system setups  

Ideally, the space used should be an interior room with no windows.  When the lights are turned off, the room should be dark with the exception of light from existing exit signs.  Several night lights (5-Watts) can be plugged into electrical sockets to provide low ambient light.  For every four or five students, there should be one setup as explained in "Simple Holography". The laser light from each setup must be shielded so that it will not reach into the vicinity of another setup.  Also, when one setup is being used, the commotion and vibrations must not be transmitted to other setups.  For this reason, each setup should occupy its own table.

If an interior room is not available, then all exterior windows need to be blocked by black plastic sheets, making certain that there is no fire code violation.

Layout for chemical processing

It is to be understood that the above information is like instructions for a theatrical stage play.  A basic rehearsal is recommended with the students is recommended before you start.

  • Each student is given a pair of chemical eye protection glasses and one rubber glove.

  • To prevent cross contamination of chemicals, each student should use a separate set of disposable trays (weighing dishes) for processing chemicals, but share buckets of water for rinsing.  However, water for rinsing after development must be separate from that after bleaching.  If running water is available, it can be used for both.

  • Assuming 2.5x2.5 inch PFG-03M plates are used, only 60 cc (milli-liter) of A+B developer and the same quantity of bleach are needed for each hologram.  Thus, before the workshop begins, the instructor can pour out as many trays of developer and bleach solutions as there are students.

  • Even in semi-darkness, the developer is seen as a clear liquid and the bleach is green; so there is no confusion. 

  • After each hologram has gone through the chemical processing and is washed, the final two steps are soaking in a Photoflo solution (optional, but strongly advised) and drying.  We recommend that this be done in an adjacent room, unless the main room is large enough that lights for viewing finished holograms are not interfering with the making of holograms.

  • To prevent dripping on the floor, each student is given a tray (or a disposable paper plate) when transporting the wet holograms from place to place.

  • The traffic jam usually occurs at the area where drying and viewing takes place.  Here, one or more buckets of Photoflo solutions are provided.  Ideally, each students can use another weighing dish with Photoflo to keep each hologram clean.  After a 20-second soaking, the hologram can be held by the edge and blow-dried with warm air from a hair dryer. The only way to avoid the traffic jam is to provide many hair dryers and as many viewing lights.

4.  SUMMARY

Assuming the reader has read "Simply Holography", he/she should practice privately the making of reflection holograms using the above additional guidelines.  The next step is to make holograms in front of an audience. With the experience thus gained, workshops can be offered to a broad range audiences.