Wrapping yourself in aluminum foil isn't enough! The kinds of radio waves used with RFID are tricky and can penetrate all sorts of things---it's a matter of power and antenna size. On a quest for a modern-day magic shielding cloth, I discovered how to make an effective, rigid pouch on the cheap.
- Holds passport, 4-8 credit cards & moderate amount of folded paper.
- Shields when closed, even when directly on top of readers.
- Cards in can-lined pockets are shielded when pouch is open, also when on reader.
- Inexpensive, readily available materials. Time is most expensive item on this project.
- Pouch design works with the strap worn on the body or without & carried in another bag.
- Shields more than some items currently available for sale.
More technical details on page 21. Non-commercial use only, please. I made a batch for sale, but do not plan to be doing any more production. (There are about 3 left.) My personal motivation for this project was not pouch sales, but was in a sense my way of distributing "free condoms" for your personal info/privacy. Of course, I'm open to other opportunities. Contact me for more info.: saraheartburn (at) gmail (dot) com.
Thanks, have fun, & be safe(r)!
Step 1: Standards and materials for the whole project. BE SAFE.
B. All measurements are in INCHES followed by CENTIMETERS IN PARENTHESIS.
Example: #4, 3 3/4 x 1 7/8 (9.6 x 4.8)
C. Any time you're instructed to 'fuse' or 'iron' it is implied that you are doing so BETWEEN two sheets of parchment paper, AND THAT YOU'RE WORKING IN A WELL-VENTILATED AREA! Bre Pettis of Make made an awesome podcast on how to make a messenger bag out of trash bags. It shows in detail how to fuse plastic trash bags together. Watch it! Make a Messenger Bag out of Trash Bags
D. Use a zipper foot for all sewing
E. The photos shown are a collection from making several different pouches. Some of which are before I added the angled pockets to the design.
- Black trash bags--(Husky brand) heavy duty 'construction cleanup'
- Clear trash can liners of the same size --(Husky brand)
- Aluminum cans
- Aluminum sheet metal .032 (.08) thick
- Box cutter utility knife w/strong blade
- Xacto knife and No. 11 blades, or blades of that shape
- Straight edge
- Cutting surface (self-healing mat or thick cardboard)
- Strong utility shears or tin snips
- Medium grain sand paper
- Medium file
- Iron & ironing board
- Parchment paper, the kind used for baking
- Sewing machine with medium to heavy duty needle, zipper foot. Intermediate sewing skills are very helpful.
- 3/4" (2) wide Velcro. Self-adhesive is great for positioning.
- 1/2" (1.3) or 1" (2.5) wide masking or other paper tape
- Black electrical tape
- 60" (153cm) of 1/8" (.32) thick screening spline (looks cool with the fused black plastic) or any kind of cord for a strap
- band saw
- mini iron--used for applique ironing
- block for sand paper
- The clear trash can liners could be optional. You wouldn't be able to see the cans you used--which is a fun design element and also makes it much easier when you're stitching the pockets. Flip the can over so that no printing is showing if you are offended by logos, etc.
***EXTREMELY IMPORTANT:*** Ironing or melting any kind of plastic produces toxic fumes that are colorless and often odorless. Do this in a well ventilated area. Well ventilated means a garage with the door open; out on your patio; a large room with a window and door open & fan blowing out the window for generous cross ventilation. Seriously, these fumes can possibly make you very sick or dead. If at any time while you are fusing plastic you feel woozy or headachey stop immediately, and get outside for fresh air. Then increase the ventilation in the area you are working in.
Wear eye protection when you're cutting and filing metal. You should probably wear eye protection when you're sewing around the aluminum. At one point I hit the sheet metal by accident and the needle shattered and hit me in the face.
Always use a sharp blade when cutting. As soon as you have the thought "this is starting to get dull..." replace the blade. The cost of extra blades is much less than a trip to the ER for stitches, and ensures clean edges on your projects. Always be mindful of the position of your hands vs. the potential path of a blade: thumb on ruler, etc. especially when sawing into aluminum cans with a utility knife.
Step 2: Cut, file, sand aluminum sheet metal pieces: #2, 4 1/2 x 5 1/2 (11.5x14)
b. File off any rough parts. Burs and sharp edges will quickly wear through the plastic. Files work best with a forward action.
c. File corners until round, 1/4" (.65) corner radius.
d.. Sand all remaining rough and jagged bits until smooth.
Step 3: Cut aluminum can pocket panels: #4, 3 3/4 x 1 7/8 (9.6 x 4.8)
b. Using the shears, cut the aluminum can tube lengthwise so you have a rectangle. Bend and work the pieces gently in the opposite direction of the curve. Make them as flat as possible without putting too many dents in them.
c. Cut paper pattern pieces: #4, 3 3/4 x 1 7/8 (9.6x4.8)
*Shortcut* fold your paper into four layers. Measure on top and cut out all four pieces at once using your straight edge and xacto.
d. Consider how you want the printing of the cans to be viewed when you tape the pattern pieces on with masking tape. The front, bottom pocket will show the most, while the other pockets will show just a little of their top. Cut each rectangle out with the shears.
e. Cutting off as little as possible, round the corners with the shears. Corner radius is approx. 1/4" (.65).
Step 4: Cut plastic bags
#21, 8x8 (20.5x20.5) black squares + several extra pieces for testing how to fuse
#21, 8x8 (20.5x20.5) clear squares + several extra pieces for testing how to fuse
(These are 'soft' measurements. If you're off +/- a half inch or so, it's OK)
a. Cut plastic bags using a straight edge & Xacto. The different bags I used were almost the same size, so that made things easy.
b. Unwrap one bag from the roll. Do not unfold the bag. It's easier to cut strips off while the plastic bag is still in a long, folded strip. Draw the bag across your cutting surface and cut off strips approx. 8" (20.5) wide.
c. Unfold those strips so they are at #4 layers thick. Slice off the folded ends so you end up with a neat stack of plastic bag strips. Cut in half for your squares.
**Important Note** these bag cutting instructions and quantities of layers relate to the size and kind of bags I used. Improvise for what you have available to you. The goal is to have layers of bags as uniform in dimension as possible.
Step 5: Fuse layers of bag together to make the main body and plain pocket pieces
make #2: #3 layers of clear squares on top of #3 layers of black squares to make one 8x8 (20.5x20.5) sheet. These become the passport and angled pockets. Set aside.
Remember to fuse between sheets of parchment with a lot of ventilation around you. Do not contact the plastic directly with your iron. If you do it will melt immediately, so wipe it off the iron with a dry rag while the iron is still hot. The temp that worked on the iron I used was just between 'wool' and 'cotton.' Keep your iron moving at a slow and steady pace using moderate to firm pressure. Adjust the iron temp as needed. Some plastics fuse and shrink more than others. When you combine plastics that shrink differently, you get curling.
a. Test fusing only the black pieces together, then fusing the black plus clear together. It should not bubble, but it may make an interesting puckering pattern. In the messenger bag video they recommend using wax paper, but I prefer parchment. The same two pieces can get you through the whole project. When you are melting and fusing properly, the plastic looks like it becomes a little greasy and sticks slightly to the paper.
Test fusing: Place #4 layers of black plastic bag between two pieces of parchment paper. Run the iron over for a little bit. Flip the whole parchment paper & plastic sandwich and iron the other side. Get a good feeling for how much you need to iron to get it fused together. I used a piece of thick aluminum sheet metal to rub the surface of the sandwich to suck up the heat and help keep the pieces from curling. Check the plastic to make sure it's one piece and not still in layers. Re-iron if needed. Next try fusing three layers of clear to three layers of black. Save the test pieces you've made for testing how the material goes through the sewing machine and making appropriate adjustments for tension.
b. When you think you have mastered fusing, proceed to fusing the work pieces listed above.
Note: The quantities listed for how many layers you fuse together relate to the thickness of the trash bags I used. If you use thinner bags you'll have to fuse more layers together. The clear liners I used were thinner than the black bags. You want to end up with thick, but still flexible material. The pocket pieces should be slightly thinner and more flexible than the main body pieces.
Step 6: Fuse aluminum can pieces into squares of plastic
a. Lay down #3 layers of clear 8x8 (20.5x20.5) squares. Whichever side of the can you wish to have visible, place face down upon #3 layers of clear plastic. Center can piece in the square, a good 1" (2.5cm) from the top. Fuse. Repeat for the other three pieces.
When I ironed my can pieces, I found that the clear plastic shrinks more than the black and if I ironed the face of the cans too much it puckered and curled. Rubbing the 'heat sink' on top of the parchment to cool and flatten was very helpful. (Don't have a thick piece of sheet metal? Use the bottom of a frying pan.) Spend more time with the iron on the perimeter of the can pieces and keep the iron on top of the can pieces only long enough to fuse it. If you mess up, cut the can piece out of the plastic and do over. The plastic does not adhere to the aluminum.
*Optional: use only black bags and have the cans invisible. I liked the cans showing and it is MUCH easier to see them when you're sewing the pockets.
Step 7: Trim & finish the edges of pocket pieces
b. Fold the trimmed edge over to the front and firmly burnish the crease with the edge of your thumbnail: press and rub the fold firmly as if you were creasing a piece of folded paper. Make it straight across the entire width of the piece.
c. Place the piece face up and while holding the scored "hem" in place, place the other piece of parchment on top. You have to be a bit dexterous with holding the parchment and fold-over in place and avoiding ironing your fingers. Try tacking a few places with the tip of the iron and then ironing the whole side. Do your best to iron only the edge and with firm pressure and slow movements, fuse the 'hem' to the face of the clear plastic over the can piece. Do not flip over and iron the other side. Be sure it's melted to the face and not just creased over. Go slow and carefully. Check and re-iron if you need.
Shown is my small iron with a small piece of parchment under it. This was easier to show what exactly is being done, and wrangle a small area, but it's not necessary to have a small iron like this to complete this project.
Step 8: Trim and finish the edge of the passport pocket
b. With the clear layer of plastic facing up, fold the trimmed edge and over 3/8 in. (1) to the front, crease, and fuse to finish the edge in a straight line the entire width of the piece--just like the previous step. This becomes the passport-sized pocket that goes behind the can-lined pockets.
(will get a photo soon!)
Step 9: Test stitching plastic, sew the two main body pieces together
b. Lay the two 8x16 body/rectangle pieces on top of each other, aligned, and fold both pieces in half. Firmly burnish the crease with your thumbnail. Unfold, keeping the pieces aligned and nested within their creases.
c. Using the fold as a guide, apply a length of 1/2" (1.3) wide masking or painters tape as straight as possible on either side of the fold. Wrap the ends of the tape to the other side towards the center fold so that the two plastic sheets are secured and aligned together. These will be your guides for the first two stitches. *The image is showing yellow electrical tape. Electrical tape is too sticky to the bottom of the sewing foot and makes it very difficult to feed through the machine. Use paper tape!
Important note: If you do decide to use a cord to make a strap, you may wish to increase these measurements of the middle fold area slightly wider (about 1-2x the width of your cord) to accommodate the cord and allow for the bulkiness of putting more items in the pouch.
d. Stitch a straight line on either side of the tape, as close as possible to it, so that you end up with two parallel stitches, each just past 1/2" (1.3) from the center crease. Remove the tape.
Step 10: Sew the sheet metal pieces into the body
b. Close the flap and on the outside, find and burnish the edge of the metal so you can get a visual guide where to stitch.
c. Using the zipper foot, stitch a 'U' around and as close to the sheet metal as possible. Using the zipper foot properly will ensure you have a close seam and that you don't feed the metal up and under the needle. Whenever you need to stop sewing and rotate the piece in the machine, lift the presser foot and do so when the needle is down in the material. Back-tack a couple times at the beginning and end of those seams.
d. Repeat for the other side. When taping in the second piece of sheet metal, test that when folded squarely in half, both plates align on top of each other. This is very important.
Step 11: Sew the passport and card pockets together
a. Place the plain, square and hemmed passport pocket piece on your work surface, hem towards the top and facing you. Lay on top of that one of the pieces of aluminum can fused pieces. (This will be the highest pocket. Only a small strip of the can printing will be showing when finished.) Align the top of the hemmed edge of the can pocket piece 1/2 in. (1.3) below and parallel to the top edge of the passport pocket piece behind it. Use masking tape on the sides to hold in place. Stitch straight along the bottom of the can, right next to it. Stitch only the width of the can piece. Be sure to back-tack a little bit on either end of the stitch.
b. Trim the excess of the top layer 1/4 in. (.65) below the seam, straight along the entire width of the square. Remove the masking tape.
c. Take another can piece and align it just below the pocket layer you just stitched on, the same distance and parallel from the top edge of the layer below it. You can now use the edges of the cans for horizontal alignment. Tape in place. Stitch just below the bottom edge of the can, the width of the can, through all layers of the plastic. Trim the excess below the seam. Repeat one more time for the third pocket.
d. For the final, front pocket, align and tape it as you did the others. Starting where the highest can pocket meets the passport pocket behind it, sew a 'U' down the sides of all the can pieces, along the bottom and back up the other side. Sew just next to the aluminum. Back-tack an extra couple times at the beginning and end where the top pocket is attaching to the passport pocket to reinforce. While you are sewing, back-tack over the edge of each pocket piece. DO NOT TRIM OFF the excess of this front, top pocket.
Step 12: Sew passport and card pockets to main body
b. Place the sheet of pockets on top of the right side, aligning the bottom seam of the bottom pocket so it's just above the bottom seam of the main body where the sheet metal is stitched in. Center horizontally and tape into place.
c. Sew a 'U' closely around the outside perimeter of the sheet metal. Start the seam where the top of the passport pocket meets the main body and go around from there. Be sure to back-tack a few times to reinforce the top edges of the pocket. Go slow. It could be helpful before you sew to burnish the edge with your thumbnail to provide a visual guide. Going slow will allow the zipper foot to do its job and keep the needle from running into the sheet metal. Do not trim any excess.
Step 13: Cut, finish edges of angled pockets
a. Lay the pouch open with the pockets facing up. Lay the fused square pocket sheet on top of the panel where it's going to be attached. Fold back at the angle you would like for the large pocket. Approximately 45Â° is about right. Crease firmly. This will be your cutting guide.
b. Remove the creased square and cut along the crease with your straight edge and xacto to make #2 angled pieces.
c. For contrast, I made the large pocket with the clear plastic facing up and the smaller one with the black facing up. Turn the edges over to the front and fuse the 'hems' like you did for the other pocket pieces.
Step 14: Attach angled pockets
b. Tape the basted pockets back onto the pouch as shown. Like you did in step 10, run your thumbnail along the edge of the sheet metal underneath to make a crease and sewing guide. Stitch a 'U' around them the same way you did the other set of pockets. Back tack a few times over the edges of the pocket 'hems.'
Step 15: Attach Velcro, double stitch
b. Place the Velcro pieces just below the bottom seams. Test alignment by closing and inspecting before stitching. Stitch just inside the edge of the Velcro, around the whole perimeter of it, and back-tack extra on the short ends. Because of the size of my sewing machine and how rigid the pouch is, I was unable to fully rotate the pouch under the needle. Sew down one length of the velcro, back-tack across the width a couple times, and then stitch backwards back up the other side of the velcro.
c. Double stitch around the entire circumference of the body of the pouch, 1/8" (.32) from the inner seams, sewing down and around the bottom of the Velcro.
Step 16: Trim out whole pouch body and round corners
a. Close the pouch together so that the Velcro, plates and outer seams are aligned. Check alignment again! Lay the closed pouch on your cutting surface and along one long edge, and align your straight edge 1/8 (.32) away from the outer seam. Give yourself a little bit more room if your stitching is not very straight or consistent to avoid cutting into the outer double seam.
b. Apply very firm pressure to the straight edge and with a slow firm cut, slice off the excess, cutting through all the layers at once. (You may have to do this in a couple cuts.) Repeat for the other side. Do the same for the short, bottom edge by the Velcro.
c. Cutting through both sides at once, round the corners. You can get away with cutting one corner at a time if you wish.
Step 17: Fuse one layer of plastic to outside and trim
a. Lay the open pouch pocket side down on the ironing board and place #1 8x16 (20.5x41) strip of black plastic on top, allowing a good inch extra on all sides. Fuse with the iron. It takes much less time to fuse one sheet to the outside. You can always re-apply the iron if it didn't melt enough. You may wish to work some of the areas with the small iron if it didn't fuse uniformly.
b. Turn over and trim as shown. Width of trim = width of the innermost seam to the edge of the pouch + the thickness of the pouch. Trim the corners as shown.
Step 18: Fold over the edges and fuse to the inner seams to finish
b. Fold over and 'tack' some points of the long edges, then fuse the rest. The goal is to cover the rough edges and seams for a clean finished look. With the small iron it is easy to iron all the little sides and bits. You can easily hold a small piece of parchment over whatever plane or edge you wish to fuse.
Step 19: Optional: Stitch in cord
b. Using black electrical tape, tape the loop into the inside crease of the pouch. Have the part where you stitched it together in there.
c. Close and top stitch the cord into place. Back tack a few times on the edges. You will need to help push the pouch through the machine. Test top stitching a cord into a thick mass of folded fused plastic scrap if this is a first for you.
Step 20: Optional: Personalize with a fused 'logo'
Jolly Roger Design:
a. Fuse #3 layers of clear plastic together.
b. Tape paper outline on workspace. Tape fused clear sheet on top. Trace outside perimeter with black fine point sharpie. Cut out with xacto.
c. Fuse to the outside. The clear plastic can disappear into the black quickly creating a funky, printed varnish look.
Step 21: More technical bits
- Tested at 125kHz and13.56MHz on commercially produced readers and tags in the wild (Seattle metropolitan area) and in a fantastic collaborative hackerspace lab lair. We have yet to acquire use of a spectrum analyzer and related antennas to rigorously test and quantify the specific amount of shielding/attenuation... requests are out to the tooth fairy.
- Some instances tags were shielded while in the plain pockets, with the pouch open. Direction of pouch in relation to antenna affects amount of attenuation. The electromagnetic properties of the environment affect attenuation. Electromagnetism is cool and fun to learn about. Some people call antenna design a 'magic black art!' Go investigate! Did you build and then 'break' this? Let me know.
- Tested a compact sleeve available for sale. It allowed a card to be read when placed on a reader. A faraday wallet shielded when closed, but tags could be read when it was open.
- Explored shielding properties of various combinations of these materials: catalog-ordered conductive textiles, layers of aluminum foil, aluminum screen, aluminum tape, zinc plate, kittens, and special lab helpers.
- credit cards
- informed consent
- radio waves
- wearable computing
- wearable technology