Making your own "X-ray Photographs"

The discovery of invisible, penetrating rays in the 1890's ushered in a new era of scientific discovery and exploration.  It opened the doors to nuclear medicine, non-invasive medical scanning, nuclear weapons, and much more.

It began in 1895 with Wilhelm Roentgen's discovery of the x-ray ('x' for unknown) and Henri Becquerel's accidental discovery of radioactivity one year later.  The first x-ray photograph was of Roentgen's wife's hand.

Mrs. Roentgen held her hand between an electrically powered x-ray tube and a photographic plate.  The result not only reveals her bone structure but also her wedding ring.  A year later, while performing experiments on polarized light, Becquerel stumbled upon natural radioactivity.  He had stored an unexposed photographic plate in a drawer near some Uranium salt samples.  Later when the plate was exposed and developed, he discovered that the film had been fogged by the salts even though they emitted no light and the plate had never come into actual physical contact with the Uranium.

Table of Contents

• Project Idea
• Initial Results
• The Technical Challenges and the Legality of using Radioactive Material
• Safety Issues Regarding the use of Radon-Generating Materials
• Seeing Through Things
• Exposing Film Using Patients of Nuclear Medicine
• Appendix

Project Idea

Figure 2 - Becquerel discovers an invisible radiation emanating from Uranium.  Note the Maltese cross placed between the lower sample and the film.

For some time I've been fascinated with the idea of reproducing these types of images in my home lab without great cost and with relative safety. As a collector of radioactive minerals and other ephemera, I decided that I wanted to use naturally radioactive materials as the source for my 'penetrating rays' rather than an amateur electrical x-ray machine setup. Secondly, as a participant in the digital revolution, the whole concept of a darkroom with the necessary equipment and development chemicals seemed unwieldy. I knew a digital setup wouldn't provide any results but I didn't want to invest in a darkroom.

Then it occurred to me: Polaroid! Polaroid film is readily available and it develops itself. However, a workable technique needed to be developed. How to expose the film for hours or days without the need for absolute darkness? How would I develop the film reliably after an exposure was made?

The answer came from Kevin Clark of the Yahoo group, "GeigerCounterEnthusiasts". Most of the conversation on this group surrounds the maintenance, repair and collection of old civil defense-era radiation detectors. However, there is some list activity on other radiation-related topics. It was here that Clark explained his simple, yet reliable, technique for creating inexpensive Polaradiographs.

Items you'll need:

1. A Polaroid SX-70, Type 600, or Spectra camera
2. A package of unexposed Type 600 or Spectra Polaroid film
3. One metal cookie tin at least six inches in diameter
4. A few sheets/roll of aluminum foil
5. Radioactive material

Type 600 or Spectra Polaroid film is easy to find. SX-70 film is discontinued as of 2006 and it is also much less sensitive than Type 600 or Spectra. Type 600 is the traditional 3 1/4" square film area that everything thinks of when you say "Polaroid". Spectra is a slightly larger format which is used in dentistry and law enforcement. You can purchase either type of camera and film in any drug store. Alternatively, most thrift shops will have an old Polaroid SX-70, Type 600, or Spectra camera lying around. If you prefer to shop from your home, eBay always has a fine selection. An SX-70 camera can accept Type 600 film with a minor modification.

Figure 3 – On an SX-70 camera, remove the clips on either side (or sometimes in the center) using a screwdriver. When forced, they should simply pop out of the plastic mount without being damaged or damaging the film loading area. Do not damage the battery contacts (often copper colored). Once removed, the SX-70 will accept Polaroid Type 600 film. For photographic purposes, one must remember that Type 600 is 4 times as sensitive to light as SX-70. For this purpose, this difference is irrelevant.

By browsing the clearance rack in a photo store, you can purchase recently expired Polaroid film on the cheap for between $0.25 - $0.40 per exposure. Very old Polaroid film is a bad idea but film expired in the past twelve months is generally fine.

By the expensive route, you can spend $50 for a new camera and roll of film. The cheap route may take a little more time and effort, but you can get the job done for less than $5.

Setup:

1. Open the Polaroid film and insert it into the camera.

Once the film is inserted and the film door is closed, the camera will automatically feed the first item on the film holder through the camera. With a new film cartridge, this is the cardboard cover that protects the film from exposure to light during the loading process. However, it is this automatic feed behavior that we can exploit to allow the camera to automatically develop the Polaradiographs.

2. Bring the camera, and the roll of aluminum foil into a completely dark room. Wait in this room for 2-3 minutes to allow your eyes to adjust. If you see any incoming light, use a towel, clothing, or perhaps some modeling clay to plug the hole. The film we are using is ISO 600; not ultra-sensitive but even small light leaks can fog the film.

3. Take a piece of aluminum foil about 18" square and lay it on a working surface. Now, open the film door on the Polaroid camera and remove the film cartridge. With the cardboard cover removed, the surface at the top of the holder is unexposed film. With your fingers, slide each piece of film out of the holder and stack them upside-down on the aluminum foil.

4. When you have removed the last piece of film you'll feel the metal spring that pushes the film up to the proper level for exposure. Take that last piece of film and remove it. Flip it upside-down, and re-insert it into the film holder. Be sure to insert it completely to the end or else light leaks will fog the exposure from a small cutout in the upper left-hand corner of the film holder.

5. Use the aluminum foil to seal the remaining film (nine exposures) from the light. It is sometimes helpful to use a second layer of foil to ensure a perfect light seal. It is also helpful to remember by feel which side is film and which side is backing so you’ll be able to load more exposures into the film holder in complete darkness.

6. Now, take another sheet of aluminum foil and wrap the film holder with the single exposure. Be careful as the aluminum foil tends to tear around the square corners of the film holder and you are aiming to achieve a perfect light seal. This allows you to avoid small light leaks that exist in the holder even when the film is upside down.

7. All your film is protected from light so you can open the doors or turn on some dim room lighting and get ready to prepare your exposure.

Making An Exposure

Now we can prove that certain materials have radioactive properties. Here are some objects you might want to try:

- Old, unused lantern mantles
- Salt substitute or certain rock salts (Potassium Chloride)
- Vaseline glass (plates, cups, or marbles)
- Fiestaware plates and dishes
- Welding rods
- Old camera lens or vintage prescription eyeglasses (look for yellowed or browned optical glass)
- Uranium ores and minerals
- Exempt, unlicensed radioactive calibration sources
- Radium containing clocks, watch hands, compasses, dials, and gauges[1]
- Tritium gunsights and keychain fobs

NOTE: All ionization type smoke detectors contain a tiny plating of the radioisotope Americium-241. It is against federal law to tamper with a smoke detector in an attempt to expose the radioactive source. No usable amount of radioactivity can be detected on film without tampering so cross this source off your list. The penalties for tampering are severe not to mention the danger you pose to yourself and others if you ‘tamper incorrectly’.

In a dark, dim or extremely poorly lit room, unwrap the film holder and place it, film side up in the cookie tin. Place your radioactive material directly onto the Polaroid film backing and carefully close the tin. Because the inside of the tin is sealed to all light, you can allow the film to accumulate a very long exposure without fear of fogging.

Use the photos in the rest of this article to guide you on proper exposure times as they may vary between five minutes, five days, or five months. After you’ve made your exposure, return to a dark or very dim place, open the cookie tin, remove the radioactive material and insert the film holder into the camera. Once the film door closes, the camera should feed your photo, upside-down through the development rollers. The camera thinks it is ejecting the protective cardboard sheet on a new roll of film when in fact it is ejecting and developing your upside-down Polaradiograph.

Depending on your camera and how accurately you loaded the film, you will get a perfect or near-perfect development. You may notice subtle repeating dots, lines, or streaks which are caused by dirt or dust and the pressure of the rollers and rubber nubs as it develops the upside-down film. Bizarre streaks of white or yellowish fogging are a result of light leaking into the film cartridge from the upper left hand notch or the film’s entry/exit point.

Initial Results

Clark and I tested various items. The photographs below also give you a good idea of the exposure times you’ll need to get results. In my photos, I was purposefully sloppy in shielding my film from fogging. This should give you an idea of the useable but imperfect results you’ll get if you have limited access to a truly dark space. Many of Clark’s photos are taken on smaller Polaroid iZone film. This film has the same sensitivity (ISO 600) as Type 600 and the exposure times are equivalent. Polaroid sheet film offers some advantages and disadvantages which you’ll see some on some of the exposures below. Polaroid pack film is significantly harder to work with than Polaroid Type 600 and offer little additional benefit.

Figure 4 - Die with radioluminescent painted spots / Kevin Clark

 

Figure 5 - 1 uCi Americium-241 source / Kevin Clark

Figure 6 - Dice with radioluminescent paint on spots / Kevin Clark

Figure 7 - GE brand alarm clock with radium hands and face / Kevin Clark

Figure 8 - Apollo brand alarm clock with radium hands. Glass removed / Kevin Clark

Figure 9 - Thorium-doped gas lantern mantle. 7-day exposure / Kevin Clark

Figure 10 - Meter with radium-doped radioluminescent paint. Legend says "Setting" / Kevin Clark

Figure 11 – Two strips of depleted uranium metal, a single radium watch hand, a Traser (tritium encased in a quartz ampule), and Thorium nitrate. Yellow is fogging from ambient light. Brown/white is from radiation exposure. The outline of the baggie containing the thorium nitrate has been traced. The baggie is not full and you can see the concentration of the nitrate at the bottom of the baggie. The Traser generates extremely weak beta rays which are unable to escape the quartz ampule. However, they interact with the quartz to generate more penetrating Bremsstrahllung (x-ray) radiation which exposes the film.

Figure 12 - Polaroid 57 sheet film. Exposure time 48hr. From top to bottom, left to right: Tritium ampule (older), tritium ampule (newer), Vaseline glass marble, Radium tipped watch hand,
square of Thorium metal, depleted Uranium strips.

Figure 13 - Large piece of massive Autunite was placed on the surface of the Polaroid 57 film pouch. Exposure time was 48hr. Uranium concentrations not visible from the surface of the rock were clearly shown here.

Figure 14 - Torbernite sample. 24hr exposure time.

The Technical Challenges and the Legality of using Radioactive Material

While the photos in the previous section show us the power of radioactive material to expose film with their invisible rays, the next step is to use the radioactive material to penetrate regular objects and reveal their innards.

Using radioactive material is more challenging than using an x-ray tube. Building a medium-power, home-brew, x-ray generator is fairly straightforward. It can be turned on and off and its energy can be directed into a beam. Also, the frequency of the radiation can be precisely calculated (which affects penetrating ability and film exposure) and the power level can be controlled electronically.

Radioactive sources offer none of these advantages. We may only select from a short list of unlicensed or exempt (and thus legal to own) radioactive sources which have very little power. While a powerful x-ray generator can penetrate opaque plastic to reveal electrical components (like airport security scanner), unlicensed radiation sources offer less penetrating ability. Radioactive materials can never be turned off and they emit their radiation in all directions. The only way to increase power is to find a material with more radioactivity or increase the total amount of radioactive material. Lastly, most radioactive material emits energy at a variety of frequencies and particle types. Each of these varies in penetrating ability.

It is also important to note that we are not using specialty x-ray film but standard Polaroid photo film. Because regular film is tuned to respond to visible light wavelengths rather than x-rays, it takes more radioactive energy to create an image. Also, x-ray film used in medical diagnostics is black & white and designed to be extremely fine grained so that it displays extreme detail and high contrast. Polaroid Type 600 is color film (which decreases resolution), and is not particularly sharp in general. This will affect the quality of the results when compared with medical x-rays.

Lastly, we are making contact photographs made by placing an object directly onto the film. There are no corrective optics to focus the image.

There are many materials in our daily environment which exhibit natural radioactivity and many examples can be found at the excellent ORAU website and online museum.

However, only these materials listed below have enough natural radioactivity to penetrate objects:

- Unprocessed Uranium ore (autunite, uranitite, tobernite, carnotite and others)

- Thorium Nitrate, Uranyl Nitrate or other radioactive salts used in lab work

- Radium containing luminous materials (i.e. watch hands)

- A medical patient who has recently received a nuclear medicine procedure (i.e. a cardiac stress test).

While United States law allows private individuals to possess NORM (Naturally Occurring Radioactive Material) and a variety of grandfathered items (radium clock faces and watch hands), it is important to remember that it is illegal to process radioactive material in the United States without a license. Inquiries to the NRC (Nuclear Regulatory Commission) have made clear that processing may mean alteration of the material. If you dissolve the paint on a radium watch hand to concentrate or reshape it, that is considered processing. If you burn old-style lantern mantles to concentrate the ash, that is considered processing. The penalties for processing nuclear materials without a license are, needless to say, non-trivial. Therefore, it is important to stay within the law if you chose to replicate these experiments. NRC regulations can been found here. The NRC is extremely conservative in their interpretation of these regulations. If there is a chance your activity is in violation, they will probably determine that it is.  If you have a question, simply pick up the phone and give them a call.  They can be quite helpful.

Given the above rules, a tiny baggie of radium watch hands is the most concentrated source of radioactivity that a United States resident may legally possess without a license. This is the source I use for most of my own Polaradiographs. However, since such a collection is getting harder and harder to obtain, one may also make photographs using Uranium ores and minerals.

Safety Issues Regarding the use of Radon-Generating Materials

When working with radioactive material we want to take precautions so that the material is not inhaled or ingested. Often this can be assured by sealing the material behind a plastic or lacquer. However, Uranium, Thorium and Radium materials are Radon generating and pose unique difficulties.

All Uranium mined from the Earth consists of three isotopes: U-234, U-235, and U-238. Uranium-238 makes up 99.27%. Uranium-235 which is used for nuclear power and weapons exists as only 0.72% of natural Uranium. This low percentage of fissile U-235 is why Uranium much be enriched to be useful for those purposes.

All three isotopes are radioactive and decay, through a long chain of intermediaries, into stable Lead. When Uranium is found in the earth, it exists in equilibrium with these intermediaries. When Uranium is mined, these intermediaries are removed.

Figure 15 - Decay chain of Uranium-238 (includes Radium)

Radium is created as part of the Uranium decay chain shown in Figure 15. What makes it unique is that Radium decays to Radon which is a not a solid, but a gas. That gaseous form allows Uranium and Radium to spread their radioactivity in a way that other materials can’t.

When a Radium atom decays into Radon gas, it is liberated from its surroundings. Whereas previously, it may have been bound to the surface of a watch hand, now it is able to migrate to the surface and float freely in the air. When this Radon decays, it becomes a non-gaseous radioactive material (an atom-sized dust particle) which falls out of the air.

Thus, Radon creates a serious problem of radiation migration and contamination. Anything near Uranium ore (which contains radium) or Radium itself will become contaminated with a radioactive dust that settles out of the air. You can attempt to coat your Radium with plastic, lacquers, etc but it won't work. The Radon gas will, to some extent, find an escape.

So, by staying legal, we are forced to use a material that will create some low-level radioactive contamination on work surfaces. Your film holders, camera innards, subject material, and even the film itself will be coated with very low-level radioactive dust.

Disposable gloves should be used at all times and you should be mindful of cross contamination. If you touch any contaminated material, you need to change gloves before you screw a container shut or its surface may be contaminated through contact with your glove. I highly recommend the use of a sensitive alpha/beta/gamma radiation detector to confirm or rule-out suspected contamination of your work environment.

Keep in mind that this level of contamination decreases rapidly with time. After the first 48 hours, the levels of radioactivity in the contaminated materials are only 30% over background. By two weeks, they are almost undetectable. Nonetheless, the importance of cleanliness in the laboratory cannot be overstated. You probably aren’t going to kill yourself by being messy and reckless but a messy lab generates messy results.

Obviously, these experiments should be performed away from your living space. The materials used should not be used for other purposes after the experiment is complete. Do not use your Polaroid camera for other purposes. Do not store food in your cookie tin.

I use gloves to handle the Polaradiographs after they are developed. After two weeks, I wash them in soap and water to remove any residual dust. In my tests, that has reduced the photographs to background levels and made them safe to handle with bare skin.

Seeing Through Things

Visibly opaque material which would be transparent to an airport x-ray machine are often still opaque to this method because of the low-power of the radioactive source. However, while materials like bone, rock, and metal will appear as opaque, other mostly organic materials such as paper, cardboard, and flesh will appear fairly transparent.

To get a nice exposure that is more than a shadow photograph, you should focus on composite materials that combine opaque and transparent material.

Figure 16 - Matchbook w/Staple (top left), Paperclip (top right), and Lighter (bottom right). Yellow/orange splotches are fogging from ambient light. Radium Source placed directly on top of subject matter. Exposure of 16 hours.

 

Figure 17 – Matchbook with an uneven number of matches remaining. Spots are from dust specks on the camera’s development rollers. Radium source was suspended 1” above subject matter. 1” distance sacrifices sharpness for improved even coverage of the entire film surface.

Figure 18 - Keychain flashlight. The radium source was unable to significantly penetrate the plastic casing over a 90hr exposure. Source was suspended 1" above subject matter. Shadow can be seen lengthening away from center of image.

Figure 19 - First attempt. Three dried goldfish with radium source 1" over surface of subject matter. Eye socket and ribcage of center fish is clearly visible.

Figure 20 – Second attempt. Reduced exposure time as first image was overexposed. Radium source was in place 1” over the film surface. Ribcage, eye socket, and other internal features are clearly visible.

Figure 21 - Joseph Maria Eder and Eduard Valenta, X-ray study of two goldfish and a saltwater fish, 1896. This photo provides a useful comparison of professional work using x-rays to the methods described herein.

Figure 22 - Mole killed and brought home by my cat Q-Tip. Placed on sealed film pouch with baggie of radium watch hands over top. Exposure time 48hr. The high water content of the mole prevented the radiation from significantly penetrating the mole’s body. No internal structures were revealed. Film is Polaroid 57.

Exposing film using patients of nuclear medicine

 

There are a wide variety of nuclear medicine procedures that involve injecting patients with radioactive isotopes such that, after they return home, they remain radioactive for some time. This provides an opportunity for normal citizens to use patients of nuclear medicine as a radioactive source for exposing film and creating Polaradiographs.

To date, I have attempted to create Polaradiographs using my own father who was injected with 44mCi of Tc-99m for a routine cardiac stress test. Tc-99m has a half-life of 6 hours and is a pure gamma emitter. The energy of the Tc-99m gamma is the same as that used in standard medical x-rays and so similar equipment can be used to detect Tc-99m’s emissions.

Approximately 4 hours after his injection his body measured 20mR/hr at 3ft using my CDV-700 with pancake probe. My Ludlum scintillometer measured 3.3 x 10^4 counts per second at 3ft.

I taped a Polaroid 57 film pouch to his chest with a paperclip, penny, flower, and a few other items between the film and his body. He wore this for 16 hours and the film was developed.

Figure 23 - Scan of Polaroid 57 from my father with Photoshop enhanced contrast. The penny and paperclip shadow photographs are visible at the top left. The lower right shows the keychain flashlight. The other various shapes and images are a result of the film being bent and misshapen during normal body movements.

 

The 16 hour exposure was obviously not enough as the film was barely developed. I placed a number of other items under his bed sheets and they received a full 8 hour exposure but nothing at all was visible on the developed film.

Other isotopes from different tests might provide better results. Alternatively, specialized x-ray film might be required. More research in this area is indicated.

 

Appendix

a. Polaroid 612 Type film – Until recently Polaroid manufactured an extremely fast B&W film for recording oscilloscope readings and other types of data. Rated at ISO 20,000, this film has 32 times the sensitivity to light as Type 600. Theoretically, it would reduce and exposure time of 16 hours to 30 minutes. As this was a specialty film, it was always difficult to find. Even more so now that it has been discontinued. I did purchase a few packs that expired in May 1992 but they were dried up and did not work. It’s too bad as this would be the perfect film for these experiments.

 

b. One can also use an x-ray machine and Polaroid film to make Polaradiographs. X-ray usage has its own safety procedures, special requirements, and even amateur setups may be subject to state regulations. For example photos and description of a different technique, see here.

 

c. Polaroid 4x5 sheet film is available in light-tight paper pouches that contain a single sheet of film. The radioactive material can be placed directly on the surface in bright daylight without a fear of light leaks or preparation in dark space. Polaroid Type 57 film is an ISO 3000 B&W film that provides a five times increased sensitivity to radiation over the ISO 600 films. It is expensive at around $3.00 per exposure and is only available for purchase in packs of 20 sheets. It also requires a Polaroid 545 film holder to process and develop the film. This holder can be purchased used on eBay for around $50. The film can be purchased from B&H Photo Video or other online camera retailer.

 

d. I have no professional training in this area so I’m sure there are many improvements, ideas, and suggestions that I am missing. I welcome your ideas and input. Let me hear from you. Please email me at aaron@muderick.com and please use the word Polaradiograph in the subject line. Thanks!

 

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[1] As of 2007, all of these items are exempt from licensing in the United States by the NRC (Nuclear Regulatory Commission) and may be possessed, sold, and transferred legally. However, new NRC guidelines being considered at the time of this writing propose to limit the ownership/transfer of certain quantities of these materials. Before engaging in the purchase or transfer of these items, please check all current laws and regulations for your jurisdiction (state and federal).