How to make a pinhole camera and develop prints with a homemade Caffenol developer
This is a guide on how I created a working pinhole camera and a homemade developer solution to make prints using direct positive paper at home. I’m not an expert on the topic, but this is what worked for me. It’s an amalgamation of a bunch of different articles and guides that I read online.
Images taken with my oatmeal pinhole container and developed with Caffenol-C in my bathroom.
Materials + Tools
For the camera:
Empty and clean oatmeal container (approx 7 inches tall)
Black matte spray paint
An aluminum soda can
Ilford Harmon Direct Positive Paper in 4” x 5” sheets
Developer + Fix:
Vitamin C Pills
3 plastic/glass trays
Making the Camera
Clean your oatmeal container with a damp paper towel to get rid of any crumbs or dust. Use the oatmeal container to trace two circles out of the black cardstock and cut them out. You might have to trim them additionally to get them to fit.
Using superglue, glue one circle to the bottom of the oatmeal container. Glue the other one to the underside of the lid. This is just to help the lid and the bottom of the container become more opaque and light-tight.
With a pencil or pen, mark a point 2.5 inches up from the bottom of the oatmeal container. Use an X-Acto knife to cut an approx 1 inch by 1 inch square centered around that point out of the oatmeal container.
Go outside and begin to spray paint the container and lid. Make sure you cover every surface with paint: the inside, outside, and bottom of the container, as well as the outside, underside, and edges of the lid. Go over everything with a few light coats to ensure coverage, waiting for the paint to dry for a few minutes in between coats. Let the container dry completely for several hours or until the next day.
Carefully cut out a 2 inch by 2 inch (approx) square out of the aluminum can. It just needs to be bigger than the hole in your oatmeal container. Round the corners to make them safer to handle.
Take a sewing needle and puncture a single hole in the middle of the aluminum square. You want the hole to be punched from the inside of the can towards the outside. The curve of the can will follow the curve of the oatmeal container. It’s okay if the aluminum is rough around the hole on the outside.
Use glue and electrical tape to adhere the aluminum piece to the inside of the oatmeal container. Place a circle of super glue around the pinhole. Then place strips of tape along the backside of the aluminum, so that when you place it inside the container it sticks to the inside wall. Center the aluminum within the oatmeal container cutout and press to adhere. This is tricky, but once you’ve placed the aluminum piece inside the container, use additional electrical tape around the edges of the aluminum to make sure no light can leak through.
Use a few pieces of electrical tape to cover the pinhole and seal it. This will also become your shutter. In addition, tape the bottom edge of the oatmeal container; light tends to leak through here as well. Check with a light source like your phone's flashlight to see if light is coming through the oatmeal container.
About the Paper
The paper used in this process (Ilford Harman Direct Positive Paper) is unique, because it creates a positive print after you develop it. You don't need to develop a negative first; your final print will be the 4 x 5 sheet from the camera. Because it's paper, it has an ISO of about 1-3, which is much slower than film. Because the paper is slow, and a pinhole has a small aperture, the exposure times are much longer than what you may be used to.
Loading the Paper
Loading the paper needs to be done in a darkroom environment. I recreated a darkroom environment in my house by using my closet and bathroom. Turn off all the lights in the house and draw all the curtains. Hang towels and cloths over windows to ensure that your rooms are as dark as possible. Because you’re kind of “hacking” these rooms into darkrooms, you will probably only be able to do darkroom steps when the sun is completely down. It would be very difficult to reach sufficient levels of darkness in a bathroom or closet during the day. I had to load paper and develop at night.
Head into your darkroom and take the lid off your camera. Making sure your room is as dark as possible, open the box of direct positive paper. Unfold the pouch inside and remove one sheet of paper.
Feel for the emulsion side of the paper, which is smoother and more plasticky than the non-emulsion side. Place the paper inside the container, opposite from the pinhole, making sure the emulsion is facing the pinhole. You'll have to use touch to feel where your pinhole is. The paper should be curved and flush along the opposite side of the container from the pinhole.
Once the paper's in your camera, put the lid on. Because light may leak through the edges of the lid, you'll have to tape the lid onto the camera. This also prevents it from falling off inadvertently and ruining your exposure. Take the camera out of the darkroom into a room with subdued/very dim lighting. Quickly tape around the entire top edge of the lid with electrical tape.
Taking photos with your camera
This is one of the trickiest parts of the entire process. Because this is a pinhole camera, the only part of the exposure you can control is the shutter speed, which is the amount of time the pinhole is exposed to the sun. You'll likely have a bad exposure the first time around, and you'll need to go through a few (or a lot) of bad prints to troubleshoot and get a feel for your camera. In general, I found that when shooting outdoors, 45 seconds on sunny days and 1 minute and 30 seconds on cloudy days to work pretty well. Exposures indoors and during dusk/dawn will take significantly longer. These times will depend on the size of your pinhole.
To take a photo, place the camera on a stationary, sturdy surface. Aim the pinhole towards a scene you'd like to capture. Get your timer ready. Remove the tape around the pinhole to open the "shutter." Keep the camera as still as possible. Once time is up, replace the tape, using additional tape as needed to make sure the pinhole area is completely covered so light cannot come through.
Mixing the Developer
The developer that we are using is called Caffenol-C, because it contains coffee and vitamin C.
Here are the ingredients:
30 grams instant coffee
15 grams washing soda
5 grams vitamin C (about 5 pills)
1 cup of room temp. water
You can convert baking soda into washing soda by baking it in a sheet pan at 400 degrees F for an hour.
Measure all the ingredients using a kitchen scale. Take your vitamin C pills and grind them in a coffee grinder until they are very fine, or crush them with a rolling pin or hammer. In a bowl, whisk the water with all the ingredients until the mixture is even and mostly dissolved. Store the mixture in an airtight container (it will smell bad).
Preparing the Fixer
Fixer is used at the end of the developing process to deactivate the silver crystals on the photo paper so that they are no longer sensitive to light. You'll need to purchase a commercially-available fixer solution for this.
To prepare the fixer, dilute the fixer according to the ratio for fixing film. For the fixer I used, this was a 1 to 4 ratio, which means for developing my paper, I mixed a quarter cup of fixer with 1 cup of water.
Developing Your Prints
In your darkroom, prepare 3 small plastic trays to hold your solutions. I laid them out in a row. Fill your first tray with the Caffenol-C solution. Fill the second tray with room-temperature water. Fill the third tray with your diluted fixer.
I used a darkroom timer app to time my development. Prepare the app with the correct developing times (below) and turn the screen brightness all the way down and make sure the app is in "Darkroom Mode" (it should look red). Try to keep the phone in your pocket and keep the screen away from the paper.
Turn off the lights and make sure your darkroom is as dark as possible. Remove the tape from the lid of your camera and take the paper out. Place the paper in the Caffenol-C, emulsion (smooth side) up. You will develop it for about 5 minutes. Wear gloves if you are handling the paper directly, as the solutions can irritate your skin. Alternatively, use wooden or plastic tongs or chopsticks. While you are developing, you need to constantly agitate the paper. This means gently move the paper back and forth within the solution.
After five minutes in the developer, move the paper to the water tray. Agitate constantly for 30 seconds.
After thirty seconds in the water bath, move the paper to the fixer tray. Agitate constantly for 3 minutes.
After you've fixed the print, you can turn on the lights! Hopefully you have a beautiful print in front of you. Take the print to the sink and rinse it under running water for five minutes.
After rinsing the print, hang it up to try. I used a clothespin. After it dries, the print will be curly. Place it under a stack of books for a day or so and it should flatten out.
After developing, clean up. The Caffenol can be returned to an airtight container and be used to developed 2 more prints. The fixer can also be reused.
Your first few prints will likely be unsatisfactory. The tricky thing about this process is that it's hard to troubleshoot, so you should be as thorough and careful as possible during each step. If your finished print looks too bright, shorten your exposure time accordingly. However, it could also indicate a light leak or exhausted developer. If you print looks too dark, lengthen your exposure time. If your print has other issues, such as large bright patches, there could be a light leak in your camera or your paper might've been exposed to light sometime during the loading process.
Make sure your darkroom is as dark as possible. Make sure your developer isn't exhausted; you should probably mix a fresh batch of Caffenol after a few prints. You should also lengthen the development time after each print by around 30 seconds. So for your second print using the same batch of caffenol, develop it for at least 5 minutes and 30 seconds. If you're concerned about your caffenol during your third print, you can also replenish it by adding a bit more coffee, vitamin c, and washing soda.
It can be a very tedious process, especially if you keep on getting unsatisfactory prints. In addition, it takes a full day to make a print since you have to load and develop at night. If you decide to try this, keep in mind that a lot of things can go wrong and you should keep trying and maintain patience. I would say about 40 percent of my prints were satisfactory. Feel free to email me with any questions!
Using other cameras
Below are a few photos I captured using the same development process, but with a professionally manufactured pinhole camera with a film holder. You could even use this paper in a 4x5 view camera.
Thanks to Allissa Chan for proofreading, as well as Zhiyao Li and Maggie Chou for tips. Thanks to The Frank-Ratchye Studio for Creative Inquiry for helping fund this process with a Residency-in-Your-Room Fellowship.