PhoneType: Photochemical Prints With a SmartPhone





Introduction: PhoneType: Photochemical Prints With a SmartPhone

We've become accustomed to taking digital photos, but at the expense of creating physical prints. So I thought that it would be pretty great if our smartphones could be used in a creative way to fill this void. After a lot of experimentation, I discovered that older photochemical processes could be modified to fit our cellphone's display. Traditionally these processes would use a method called "Contact Printing," by which a film negative or piece of acetate/polyester containing a negative image would be placed on coated paper. After exposure to Ultraviolet light (sunlight), a positive image would be formed. Our phones don't emit UV light, but they do emit blue light, which is close. And as it turns out, by modifying one of these photochemical processes (The Kallitype), you can make a photochemical piece of paper that's sensitive to blue light! And thus, sensitive to your smartphone!

You will need the following:

- Dim Tungsten Lighting, or (ideally) Red Lights. Red christmas lights will work great!

- A clean, dry painter's brush. Try to use smaller sizes so as to better control how much chemistry you use.

- Cotton Rag Paper, sometimes referred to as watercolor paper.

- Glass container or shotglass. It's important you don't use it for food or drink.

- Silver Nitrate, 12% solution. This can be a bit expensive. You can buy silver nitrate (powdered) from Bostick and Sullivan: If you want to save time from making your own solution, Bostick and Sullivan offers this bottle that just needs warm water to mix: If too expensive, you can get away with this less concentrated bottle:*

- Ferric Oxalate, 20% solution. Please just buy this readymade solution from Bostick and Sullivan to save yourself the trouble of mixing it yourself: -- It's annoying to mix, trust me

- Sodium Citrate Developer: -- This stuff "develops" the image on your print. You'll get the best quality with this one.

- Fixer. This stuff makes your print permanent and cannot be skipped! Sodium Thiosulfate Crystals that can be bought here: along with Household-grade Ammonia:

- Citric Acid. While this can be bought in a variety of places and is food-safe, I recommend buying it through Bostick and Sullivan for purity (to group it into one order):

- Nitrile Gloves. While nothing in this process is toxic, you don't want to accumulate silver in your body, so wear these for protection.

*While the 10% solution works, your exposure time for making a print will be much longer and you should really double coat (coat the paper once, then coat again after 8 hours of drying).

Step 1: Set Up Your Space (Table, Lighting, Chemistry, Paper)

You'll need a clean working space that is preferably white or light-colored. Because you'll be working in low light (see the next step/video), a bright table to work on does wonders for seeing what you're doing.

The Silver Nitrate and the Ferric Oxalate (pictured in the larger photo) should be mixed and stored into dark amber dropper bottles. If you didn't buy the Bostick and Sullivan readymade solutions, you can get away with clean glass dropper bottles that are covered with black tape/cloth. It is important that neither of these compounds get exposed to bright light for extended periods of time.

I recommend differentiating the two dropper bottles in an obvious way. When you're not used to doing this it's easy to get mixed up. It's common to make the silver nitrate bottle the smaller of the two, since it's more precious anyways.

Now set these two chemicals off to the side and place your glass container (or shotglass) near them. Then place your brush near the paper and do whatever's necessary to make the room dim. In the video I use string LEDs with a red bulb-casing that are battery operated. Avoid white LEDs (emits some blue light) and overhead fluorescent illumination (emits a tiny amount of UV light). Again, a single warm incandescent bulb placed somewhere else in the room will be fine.

Step 2: Lights Off, Begin the Coating

I recommend watching the video for these next steps, but I'll provide some more written explanation here.

Take the dropper bottle that contains the Ferric Oxalate and add 15 drops to your glass container. This stuff is relatively harmless, but be careful and don't be messy. Now take the dropper bottle that contains the Silver Nitrate and add 15 drops. Be extra careful here, as Silver Nitrate solution must not get into contact with your eyes. In the video I'm not wearing gloves, but it's possible that even when you're super careful that somehow, somewhere in the process you'll notice little black spots on your fingers. Don't be alarmed! These spots should disappear in a couple of days and are just tiny bits of silver nitrate that bonded with outer layers of skin. When the old skin sheds they'll be gone (weird I know). If this bothers you at all, please wear the nitrile gloves.

Give the container a little swirl to mix both, then take your brush and dip it in.

How you coat the paper is up to you, but for "evenness" in the coat you want to alternate between long and short strokes. Try to coat the size of your phone's screen, or a little bit larger if you'd like a border. While my phone is on the smaller end, you can certainly do this process with a tablet too.

Once coated, you *should* leave the print to dry in a dark place for 8 hours. You want the paper to be "bone dry" too, so try to avoid damp or humid places. Letting the paper air-dry allows for better image quality. You can heat the paper with a blowdryer, but keep it on a low setting only!

Step 3: After Drying, But Before Placing the Smartphone...

You need to (temporarily) invert your smartphone's screen colors.

I'm using an iPhone in the video, but don't turn back now! Android smartphones can also do this process! A quick google search tells me that on Samsung Galaxy phones it's found in the Accessibility settings. I would imagine that this is the case for most of the phone manufacturers, but regardless this is a very common feature so your phone should have it.

Regardless, on iPhones with the current iOS 11 (effective 3/19/2018) it's under General > Accessibility > Display Modifications > Invert Colors. Then you select Classic Invert.Your screen will be inverted! This is essential for your print to have a positive (normal looking) image. In an inverted image, brighter sections are what used to be your blacks in your photograph, so in order for them to be black on the print they need to be bright on the screen to give enough exposure to the print. This same principle is found in traditional black and white photography and film.

In the video I suggest using a moody photo, and essentially I mean that sunny beach shots probably won't look that well with this process unless you leave your phone on the paper for hours. So try to pick photos that were shot at sunset or indoors, and if the photo is of someone else, look for images where the light is illuminating them from the side, instead of from behind them.

Now, you need to make sure that your phone's screen doesn't turn off during this process. It's essential that you double check your phone's energy saving or auto lock settings so that it will stay on for the whole 30-40 minutes that it's lying on the piece of paper. On iPhones with iOS 11, go to Display and Brightness > Auto-lock, and set it to Never.

Finally, before pulling up your photo, if you're using an iPhone, you need to swipe up from the bottom of the screen and hit the Portrait Orientation Lock. A quick google search tells me that on Samsung Galaxy phones you tap and drag the Notification bar downwards.

You're ready to expose! Now maximize the brightness on your phones, check to make sure it has enough charge (for 40 minutes it uses 15% on my iPhone), and...

Step 4: Place Your Smartphone on the Paper!

Screen down, of course. As shown in the video, I recommend adding some extra weight. This will create a firm adhesion with the paper, and will boost the sharpness of your resulting print.

Exposure time will range from 30 minutes to an hour usually. I do notice more consistent performance if the photo is black and white. This is probably because more of the blue pixels in your phone are activated when the phone is projecting more "white" light.

By the way, it doesn't really matter if this is done in a dark room or not, but try to do it in dimmer lighting so as not to "fog" (expose) the edges.

Step 5: Inventory Check: the Necessary Chemistry

While you're waiting for your print to expose, I'll go over the chemistry for the next steps.

The Sodium Citrate, which develops the image (literally makes an image appear on the print after exposure), is safe and reusable. You can probably squeeze 50 or so prints out of a single bottle.

Citric Acid is a mild acid found in Lemons and Limes, and is mostly harmless in its pure form. Handle it with respect of course. It's important to have this because you need to slightly acidify a washing bath that occurs after development but before the "Fix."

The Fixer is composed of Sodium Thiosulfate and Household Ammonia. Once again, it's essential that you make this stuff. Even if an awesome looking image appears after development, it will not be permanent unless you "Fix" it. Fixing the print removes excess silver salts that weren't exposed, and thus ensures permanence of your image. To make, take roughly 50 grams of Sodium Thiosulfate and dissolve it in distilled or filtered water. I don't include any measurement tools in my required items list because if you buy the 100 grams from Bostick and Sullivan, you simply need roughly half the bottle/package. After it's completely dissolved in the water, add 5 milliliters of the Household Ammonia. If you don't have a metric measuring tool, then simply use 1 tsp (teaspoon) of Household Ammonia. Your Fix is now prepared. This stuff is also reusable, and once it touches a print, it's very important you don't dump it down the drain. It quite literally will accumulate silver over usage. Fortunately it can be used a lot, and just filter out any sediment that builds up in it (overtime) with a coffee filter. When it finally is unusable (when it's either near empty or darkly colored), consult your county chemical authority for disposal instructions.

Get your nitrile gloves ready for the next steps. Once again, there's nothing toxic happening in this process, but wearing the nitrile gloves is important so that you don't accumulate chemistry in your skin...

Step 6: Developing the Print

After perhaps 40 minutes or so, your print is ready to expose! Before putting it in the tray (plastic or glass only), look for a "whisper" of an image. If you see something, even if it's reeeeally faint, then the print was exposed.

Now, put the print in the tray, and pour the Sodium Citrate over the print. After about ten seconds you should really start to see your image come in. The print needs to sit in the tray for 8 minutes. It's important to rock the tray (agitate it) ever 30 seconds or so. This ensures fresh chemistry is hitting the print. This may seem tedious, but your image will gradually get a bit darker during this period, so stay the course.

Step 7: An Image Formed, Time to Wash

After 8 minutes you should have a fairly realized image. The one pictured above is a photo of a friend of mine.

Wearing the nitrile gloves, pick up the print and place it in another tray* of fresh water (from the tap) with a healthy pinch of that citric acid thrown in. Ideally this tray is near running water, and after having the print sit for a second, start running water over the tray and print and leave it there for a minute. The citric acid is important because it "buffs" the print against the much more alkaline Fixer, preventing bleaching of the image.

*If you don't have another tray, return the developer back to its bottle for reuse, fill the tray up with some water (print included), dump it, then wash it again with the citric acid and the running water.

Step 8: The Print's Washed, Now to Fix It

After washing, put your nitrile gloves back on and pick up the print. Let it drip over the tray for 10 seconds, and then place it in the Fixer and immediately start agitating (rocking the tray). Leave it in for 1-2 minutes. 1 minute is fine if the solution is fresh, but over time and use, head towards 2 minutes.

You'll notice a slight darkening of the image. This is good! It means the Fix is working correctly.

Step 9: After Fix, the Final Wash

Put the nitrile gloves on one last time. Pick up the print, let it drip, and place it in a clean tray full of running water. This final rush will ensure that excess iron salts are removed from the print, preventing oxidation of the metallic silver and granting the print better permanence. So long story short, you need to wash it thoroughly. I recommend filling the tray and dumping it for the first 5 minutes, and then for 15 minutes let the running water just overflow the tray.

Once the wash is done, pick the print up with clean hands and place it on a drying rack or screen. Over the course of 12 hours the print will darken significantly. If you like the way it looks now, you'll probably really like it then, so be patient.



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    4 Questions

    So you've previously answered which kind of cotton rag paper to use but I'm still very confused, what is it???


    Fantastic instructable! Thank you for sharing your knowledge :-) I have two quick questions for you. 1) You mention using cotton rag. When looking around for suppliers today, I ran into a wide variety of weights and finishes and textures on the paper. What recommendations do you have for the paper types? 2) When buying chemicals in granular form, do you have any guidance on how far things will stretch? If I buy the silver nitrate granules, for example, they're vailable in 10 gram, 25 gram, and bigger sizes. What's an appropriate amount to purchase? Thanks again!


    Thank you very much! What cotton rag paper you use is largely up to you, but I recommend something that's a little bit thicker. Stonehenge White is great, and is what was used in the video. For this process you'll need 12 grams of Silver Nitrate in 75ml of water, and then once completely dissolved, add enough distilled water to make 100ml. It will probably be able to make 25 or so prints, factoring in some mistakes here and there. Hope this helps!


    Brilliant! Have you tried this process with cyanotype?


    Thanks! The traditional Cyanotype won't work with this process because Ferric Ammonium Citrate/Potassium Ferricyanide need UV in order to convert into new iron salts. However, I have not tested the "New" Cyanotype process, also known as Mike Ware's Cyanotype. That process uses Ferric Oxalate (also used in this process), which I believe is more light sensitive. You can do some research and some experiments, but even if it did work, exposure times would be very, very long.

    1 more answer

    Great question..Cyanotype needs UV. I have a old screen I completely separated from a laptop and will be trying this when I get my butt in gear.and make a uv box.

    this looks very exciting. Could you tell me if, after coating the paper with silver nitrate, can one use conventional black-and-white photo paper chemicals to develop the paper image or must one use the precise chemistry that you describe ? Thanks for this information.


    Thank you! Conventional B&W Chemistry will not work. They're filled with a lot of chemicals that are unnecessary for this process. Sodium Citrate is not the only option, however. Because this process is based on the Kallitype, other Kallitype or Platinum/Palladium Developers may work. So far I've only tested Ammonium Citrate and Sodium Citrate, with Sodium Citrate performing a bit better.


    Bastante interessante mas muito demorado. Podemos utilizar para fotos um papel fotografico de contato e os quimicos pode ser adquiridos prontos - Kodabromide e o interruptor entre o revelador e o fixador usar o acido acético glacial na proporção de 10%. O local para fazer isso tudo deve ser escuro, somente uma pequena lâmpada de vermelha de 30 ou 40 watt. Cortar o papel nesse ambiente protegido no tamanho da tela do smartphone. O procedimento de copiar a imagem da tela para o papel e mais rápido - 10 segundos de exposição e revelação em 30 a 35 segundos, interrupção da revelação 10 a 20 segundos e fixação de 5 ou 6 minutos. Após lave o papel em água corrente e deixe secar ou seque-o proximo a uma fonte de calor... um ferro de passar roupa por exemplo. Até os anos de 2015 e 2016 fazia muitas experiências com meus alunos na escola. Era sucesso. Mas você está de parabéns pelo post.

    2 replies

    Thank you for your insight! It's important to remember that the process you describe requires a true darkoom and safelight in order to avoid exposure. Because this process is modified from the Kallitype, only dim lighting is necessary, like a single tungsten bulb placed somewhere in the room. While similar in the end result, the process you describe is quite different, being limited to precoated gelatin silver papers.

    Detalhes - Você tem razão nesse aspecto. Apenas quis acrescentar alguma coisa a mais. Mas estou me preparando para seguir seu método. Depois lhe passo um feedback. Sucesso!

    Brilliant. thank you. Can tis be used on a tablet or laptop screen? Or even a monitor for larger prints?

    1 reply

    Thank you! It will also work with a tablet/laptop screen/monitor. You'll need to do some creative mounting in order to get a nice, sharp image from a laptop or monitor screen. Remember that being able to make firm adhesion creates sharpness, so a tablet would be easier.

    This is the most awesome Instructable I've seen yet. I have one question: Could ordinary fixer for B&W film or paper be used as well as using ordinary acetic acid stop bath instead of the citric acid (or skip the citric acid altogether)?

    1 reply

    Thanks for the praise! Ordinary Fixer may bleach the image, unfortunately. This process is based off of the Kallitype, and it's important in that process that the Fixer is only slightly alkaline. Acetic Acid Stop Bath may work; I would recommend diluting it significantly though with water. It's important to understand that the middle step in this process isn't really a stop bath in a traditional sense. The Citric Acid and the wash helps clean the print of developer or unused iron, as well as slightly buffing it against the alkaline Fixer. Hope this helps!

    This is beautiful. I love how this combines an old analog craft with a fast-paced digital throw-away medium. Thanks for sharing

    1 reply

    Thank you so much!

    This remind me of the days I spend with my father defelopping Pictures. Very intresting to use your phone.

    1 reply

    Mhm, I love developing pictures with chemistry too. I'm glad you found this interesting!


    nice. I often thought about using a media projector to print pics, just make the image negative and should work.

    1 reply

    Yeah! That might just work! You would just need to make sure that the projection is really bright, and be sure that it's emitting blue light.

    Very interesting process! Nice to see stuff like this, thanks!

    1 reply

    Thank you!