Making your own phone case from a composite layup is surprisingly simple. Through this process you can make a durable, personalized case for any type of phone, complete with any decoration you see fit to add.
Step 1: Creating the Mold
To begin, you will need plaster, cling wrap, and a hard plastic case for the type of the phone you intend to make a case for. The case could be an old one you want to make a replacement for or a case borrowed from a friend.
Before you start, you probably want to lay out some protective layer over your work surface, such as a layer of plastic or newspaper.
First, make sure the case is clean so that the cling wrap will stick easily to it. Wash it with soap and water and dry it thoroughly. Tear off a piece of plastic wrap larger than the case and press it into the case. Ensure that the wrap sticks to the case and conforms to the inside of the case smoothly and completely. Make sure it sticks to the insides of the corners of the edges so that the new case will grip the phone without issue. Push the wrap out through any holes made for chargers, headphones, buttons, or cameras; this is important to make sure the new case has these holes.
Once the cling wrap has been put into place, begin mixing the plaster, making enough to fill up the case with a little bit of excess. Mix the plaster quickly and don't spend too long trying to get the mix just right, or else you may end up with a cup full of solid plaster. Pour the plaster into the case, making sure that it flows into the corners and into the plastic wrap that sticks out through the holes in the case. Let the Plaster harden and move onto the next step.
Step 2: Starting the Case
Once the plaster is solidified, you should be able to remove the case from the mold as you would from a phone. Depending on how much plaster sticks out, you may need to chip some off, leaving enough that it will be obvious even once it is wrapped up.
For this step you'll need waxed paper, tape, a clear epoxy and something to apply it with, and the fabric or weave you intend to make the case out of. (I used a carbon fiber weave, but anything flexible enough to wrap around the phone will do)
Cut your weave to a size larger than the mold, making sure it will cover at least as much as the case did. If you are using carbon fiber you will probably need tough scissors, such as kevlar scissors for this. Wrap the mold in the weave, folding it around the edges. Make sure it conforms to the protrusions where the holes in the case were, as well as the corners. Keep in mind that the alignment and quality of this wrapping will carry over to the final product, so take your time. You may want to cut into the corners of the weave to let them wrap around the corners with less folding.
If you use a loose weave like I did, be gentle around the corners. The weave can easily unravel there if you aren't careful.
Set the mold down so that the weave is held in place and mix the epoxy. You'll probably want a slower-setting epoxy for this, as it will have to set after the third step. Apply the epoxy to the weave, making sure you cover all of the entirety of the weave with an even layer, including the back.
At this point it is possible to add some decoration to the case. Pieces of thin paper or fabric placed on the flat front of the case will be visible in the final product.
Once the case is covered in epoxy, wrap it in waxed paper and tape the paper into place. Be sure to wrap it tightly enough that the weave is held tightly to the mold and quickly move on to the next step.
Step 3: Sealing and Hardening the Case
Once the epoxy is applied, this step will have to be completed before it significantly hardens.
You will need a vacuum sealing bag or a sheet of thick, flexible plastic, an air pump, and sealing clay.
Prepare the bag or plastic for vacuum sealing. If you are using a sheet, fold it in half and seal the edges with the clay, leaving room for the pump and to insert the case. Place the paper-wrapped case in the bag and insert the air pump's tube. Seal the opening with clay and start the pump.
As the bag empties of air, make sure the bag is conforming to the shape of the case, rather than deforming the weave to fit the bag. Push the bag in around the edges of the case.
Listen for any hissing noises made by the bag as the pump runs. These indicate leaks, which can be sealed with clay.
Let the pump run until the bag is completely devoid of air and conforms completely to the case. Now that the case is sealed, allow it time for the epoxy to completely cure before moving on to the next step.
Step 4: Cleaning the Case
Once enough time has elapsed for the epoxy to cure (wait longer than the time listed on the epoxy's packaging) you can remove the case from the bag and unwrap the waxed paper.
For this step you will need a hammer, a chisel (or flat-head screwdriver), and a razor blade, preferably with a handle.
The waxed paper may stick to the case and tear when you remove it. Carefully use the razor to peel these torn pieces of waxed paper from the case. Once as much paper as possible has been removed in this fashion, set the case face-down on the protective surface.
You may need to trim away excess weave before you begin to remove the plaster. Use the hammer and chisel to break up the plaster. Hammer blows will fracture the plaster without damaging the more flexible case. Once these cracks are present it is easier to embed the chisel in them and pry out chunks of plaster. This will likely leave small pieces of plaster stuck firmly to the inside of the case. these will need to be removed by prying them off with a razor blade. Make sure all of the plaster, including that which is stuck in the corners is removed before moving on to the next step.,
Step 5: Cutting and Smoothing the Case
Once the plaster is gone, you can remove unnecessary epoxy and weave.
For this step you will need a Dremel or similar tool with a rotary saw attachment and a small sander. You will also need to be aware of the particulates produced by this step.
Using the cutting tool, trim the case to the dimensions of the original case. Identify the areas where the holes in the case were and cut them away. Using a ten-speed Dremel I found that speed 8 was sufficient to easily cut carbon fiber. Be careful when cutting the case; remember that if the holes are too small that can be rectified, but cutting holes too large will make the case weaker and can't be fixed. Some pieces of weave at the edges may become too flexible to cut all the way through with the Dremel and will need scissors to cut them.
If the sealing went perfectly there shouldn't be any edges or burrs of epoxy sticking off the case, but that's unlikely. There will probably be edges where the waxed paper didn't stick perfectly to the weave, causing edges of the epoxy to protrude from the weave. Use the sander to remove or reduce these. Keep in mind that the sander will not be able to remove protrusions of weave, or smooth ragged edges.
Step 6: Finishing the Case
To finish the case you will give it a final smooth coating of epoxy.
For this step you will need the Dremel and sander attachment, as well as epoxy and something to put the case on to keep it away from the work surface.
The epoxy used for this step does not need to be a slow-setting epoxy, so feel free to quicken this step with a different epoxy. Because this layer of epoxy will be final surface, if you are unable to accurately mix the epoxy in the desired ratio, it is better to err on the side of excess hardener.
Once the epoxy is mixed, place the case on the stand with it's front side facing up. Paint the outside of the case with epoxy, making sure the edges and corners are adequately covered by the end.
Once the epoxy is full hardened, use the Dremel to sand off any dripping or excess epoxy. You may want to use several different grits to achieve the smoothness you want. If you so desire, you can repeat the process of epoxy and sanding on the inside of the case as well.
Congratulations! At this point your new phone case is ready to use.