Teaching Holography in Classrooms

By T. H. Jeong, Riley Aumiller, Raymond Ro, and Jeff Blythe
Edited by Alec Jeong
© 2003-2015 Integraf

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.

The 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 pracitcal 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 the formerly used GP-2 developer solutions. For a 5mW diode laser spreading its beam 40 cm from the plate, the required exposure time for the PFG-03M is approximately 5 to 7 seconds.

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. As such, the total processing time using JARB can be as short as three minutes, from developing to drying.

3. Photochemistry

The JARB formula is now commercially available as JD-4, a kit that contains all the photochemistry needed to process holograms. Formulated to work in a school environment, the JD-4 provides each chemical in dry powered form, which can then be combined with water to easily make the photochemistry solutions needed.

We recommend reading our article How to Use JD-4 to understand how to mix and use the developer and bleach solutions. The JD-4 asks you to create three stock solutions: Solution A, Solution B, and thirdly, the bleach solution. When you are ready to process your holograms, you mix solutions A and B together to create the developer.

Once you have solutions A, B and bleach ready, place trays on your lab table or counter so that they are in this order as listed:

  1. Developer (A&B mixed together) — small tray
  2. Rinse — large tray
  3. Bleach — small tray
  4. Rinse — large tray
  5. FormaFlo 600 Wetting solution (optional) — small or large tray

So, what you have above is your "assembly line" of trays placed in order. This will make easy for you and your students to process the holograms efficiently. The last step with the FormaFlo 600 wetting solution is optional but recommended, as it will help your holograms dry evenly and turn out clearer and cleaner.

4. Practical Considerations for Teachers

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

Set Up Stations for Shooting Holograms

Just like you've set up an assembly line for your photochemistry, we recommend setting up an assemblyline for the lab area where students will exposure the holographic plate to the laser light.

It's possible for 20 students to make holograms in a little over an hour relying on a single laser. However, for efficiency and so students have an opportunity to make at least two attempts, we recommend having a second or even third laser available, such as an economical and appropriate diode laser. This will allow you to set up two to three stations for shooting holograms.

Layout for Photochemical Processing of Holograms

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.

5. Additional Tips

Assuming the reader has read "Simple Holography", one 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.

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.