If you have ever been in the military or government, you have probably encountered the phenomenon of "Challenge Coins." In this Instructable, we will make an easily reproducible challenge coin of your own design.
A challenge coin is a small token of appreciation for an act that does not quite deserve a formal award, but is too significant to ignore. It can be given on the spur of the moment and in public in the recognition of excellence. The practice dates to ancient Greek times where a Soldier would carry the commander's "Coin" that would prove his identity on the battlefield and for organizational purposes. Back then, it was just a clay token that has the name of the commander, but now the coin is usually metal and highly detailed prestige peices.
You can buy challenge coins from many on-line sources, but we are makers so lets make them instead.
Step 1: Concept
I decided on a few principles for my DIY challenge coin quest:
2. Reasonably Durable
3. Easy to produce and reproduce
4. Scale-able (can make one or 100 easily)
5. Can be made without special equipment
Modern challenge coins like most other coins are generally made of metal. You can hire a company on the internet that will mint your challenge coin for a fee and usually a minimum order in the hundreds. So not an inexpensive way to go.
So, I decided to go back in time and make a challenge coin out of clay, just like those Greek Soldiers centuries ago. To make it reproducible, I'll carve the design into linoleum blocks to make a type of stamp to impress the clay. You may think linoleum is "special equipment" but you can find it in just about any hobby shop these days for relief printing.
Step 2: Stuff You Will Need
This is basically a ceramics project, so most of the stuff annotated below speaks to that. If you are lucky enough to have access to a real ceramic kiln, your life just got easier! Here I used pit firing for the clay.
1. Ceramic Clay (although you could also use polymer clay or even metal clay if you want a metal coin at the end)
2. 2x3 inch carve-able linoleum blocks
3. Linoleum carving (or wood carving) tools
4. Round biscuit or cookie cutters
5. Vegetable or mineral oil
6. Rolling pin
7. Charcoal, sawdust, wood shavings
8. Burning pit or buckets or clay flowerpots (bar-b-que grill?)
9. Tung oil, floor wax, polyurethane or other sealant
10. Paint if desired
11. Food dehydrator (not required, but certainly made life easier when dealing with clay)
Step 3: Coin Design
Design: Making a coin out of linoleum block and clay limits the complexity of your design. Just look at linoleum block prints online to see the quality of a linoleum image. This limitation actually works for you since most successful coin designs have a single bold element (per side) that has deep symbolic meaning....or just looks cool. Once you start cluttering up your design with lots of detail, lettering and decoration, the meaning gets muddled and hard to decipher.
Size: Since you are using clay, you can make your coin any size. However, the low fired clay I used and the pit firing method does not make for extremely strong coins, so it is best to keep it below two inches (51mm) in diameter. The smaller the size, the less chance of breakage. For this design, 1.75 inches(45mm) seemed like a good diameter. Also the biscuit cutting tool comes in standardized sizes, so working within those sizes will make your life easier.
Thickness: We will never reproduce the mass of a metal coin with clay, but making your clay coin thicker than regular challenge coins will go a long way to make it feel more substantial. This project ended up with coins about twice as thick as a commercially produced coin (about 1/8 of an inch or about 3mm).
Step 4: Carving Your Stamp
1. Design your image. If you are like me and have no artistic talent, the world of royalty free clipart is your friend. Remember that the imagery works best if it is bold and simple. Once you have the design you like, print it out at the size you want. If you have any lettering, make sure you reverse it in the software or sometimes print drivers will allow you to "reverse" print the image.
2. Transfer the design to the linoleum. I use the old fashion method of tracing over the image with carbon paper between the design and the linoleum block. Again, the lettering needs to be reversed if you want the lettering on the coin to be readable.
3. Carve the linoleum. Important to remember that this is a little different than block printing. What you carve away will be raised in the final image (the opposite of printing). Pro tip: if you need to make small round holes, use an appropriate sized drill bit. No need for a drill, just twist it in your fingers and it will easily drill through the linoleum and give a nice clean hole. As part of my design, I put a circle around the design to make a raised ridge around the coin. You may or may not want this.
Step 5: Make Your Coins
I used a low fire clay called ACTIVA Blackjack Low Fire Clay. It is a dark gray clay that dries to a light gray and fires to a very light gray...almost white. If fired in an oxygen free environment, the clay develops a matte black exterior. Feel free to use high fire clay if you like. It will make a stronger coin, but since I do not have a proper kiln, I chose the low firing clay so I could fire in a pit.
1. Roll out your clay into a slab. You can put dowels on either side to control the thickness. You should aim for about 1/4 thick (6.33 mm).
2. Take the cutter for the size coin you want and cut rounds from the slab.
3. Prep your linoleum blocks with a release agent. I tried corn starch which worked, but had to reapply every time. I finally decided to switch to oil. I used 3 in 1 oil, but cooking oil will work as well. It will burn off later anyway. Brush on the oil and it will last 4 or 5 coins before you reapply.
4. Take a round of clay and put it on the more complex design linoleum block. Take your rolling pin and roll the round into the linoleum stamp. The clay will spread out, but don't worry too much about this. Once you are satisfied that the design is impressed into the clay, place the less complex linoleum block on the top and press down. Tap the top block with a rubber mallet to impress the top design into the clay.
5. Separate the linoleum blocks from the clay. It should come apart easily. Take the cutter and trim the excess clay from the coin. The excess can be recycled. If you do not like the results for any reason, just recycle the clay coin and try again.
6. Lay out the finished coins on a flat surface and try to get them as flat as possible without ruining the design.
7. Once the coins are "leather hard," transfer the coins to the dehydrator if you have one. You can fully dry the clay in a few hours. If you let it dry naturally it may take a few days.
Step 6: Fire Your Coins
I wanted to use the "sawdust" firing method to get a nice matte black finish on the clay, however it didn't work out quite like I expected. I used the THIS instructable by Saranya Anandha Krishnan to design my "kiln" out of two flowerpots. Unfortunately, I layered my clay coins in the pot along with cedar shavings and created a fireproof layer that the charcoal could not burn through. So I switched to a pit fire method where the coins were in both oxidizing and reducing environments, so some turned black (reducing), some white (oxidizing), and some in between. Actually quite pleased with the variety.
For pit firing:
1. Dig a hole or use a fireproof metal bucket. Put your dry clay coins in the bottom on a layer of sawdust or wood shavings. Bury with sawdust, wood shavings, cow pies, newspaper or whatever will burn. Put charcoal and wood on the top. Use kindling and newspaper to ignite the mass and let burn down to coals. Cover with a metal cookie sheet or something metal to trap the heat.
2. Let everything burn out and cool overnight.
3. Fish out your coins without burning yourself.
4. Clean the coins with a stiff brush. You can wash off the coins with water, but you will have to dry them thoroughly before doing anything next. I used my dehydrator to dry them again.
Step 7: Decorate Your Coins
The coins do not really need to be embellished if you are happy with your fired coins, but I felt a little color would make them more fun. The work was tedious, but with all the adult coloring craze, maybe it was therapeutic? It didn't take as long as I thought...maybe two episodes of Downton Abby.
1. Find the correct color for your design.
2. Color within the lines.
3. Finish off the design with a black sharpie magic marker.
Step 8: Seal Your Coins
Even though you fired the coins, they are still porous and need to be sealed with something to protect your painted artwork and to make them last as long as you can.
You can use anything you would seal wood with to make your coins more durable. I chose oil based polyurethane since it was what I had on hand. I also tried tung oil and floor wax, but those didn't look all that great. I used glossy poly on the coins, but I'd probably go with satin or matte in the future.
1. Apply polyurethane to one side.
2. Put into the dehydrator for drying for an hour or so.
3. Apply poly to the other side and edge....back into the dehydrator for drying.
4. Repeat steps 1~3 for as many coats as you desire.
Step 9: Final Thoughts
- Nobody will mistake your home made coin for a professionally reproduced metal challenge coin, but it looks perfectly at home with coins in my collection.
- I really like the variation in pit fired clay and will try some additives that will provide flashes of color on the clay (salt, copper sulfate, seaweed, etc.). Although the coins are very small and will not display the patterns that can be on the surface area of larger pots, it still could have some interesting effects.
- I tried to break one of the coins by dropping it on the floor. It seemed to withstand the dropping just fine. However, I eventually broke it by hand (it is low fired ceramic after all). It took more effort than I expected, so I'd expect the coin to hold up pretty well in normal use. Since challenge coins are mostly display objects, it should not be too much of a problem. If you have access to a real ceramic kiln, you can make much more durable coins.
- I'd like to create flatter coins in the future. Some were cupped and made them appear to be un-coin-like. Once I have more practice, I feel I could create flatter coins.
- Enjoy your handmade challenge coins!
Step 10: Update #1 - Registration and Thickness
First of all, I changed the name of the instructable after a friend of mine mentioned that these could easily be used for geocaching tokens. They are cheap and easy to mass produce, so even if a greedy geocacher took more than their fair share, you could easily produce more.
I was not that happy with the misalignment of the front and back of some of my earlier coins. Also was not happy that the coins ended up with different thicknesses and sometimes, different thicknesses in the same coin.
To solve both by devising a better registration system that could easily reproduced, I used a larger 5x7 inch mounted linoleum block and made two coins at a time. These are 2 inch coins, so 2 per block pairs seemed good. If you produced a smaller coin, you may be able to get 4 onto a block pair.
Measure your coin designs carefully and put the two blocks face to face (insuring the registration is perfect). Then use rubber bands or zip ties to hold the registered pair together. Drill holes in all four corners of the block sandwich. A drill press would be ideal since it will give you a perfectly 90 degree hole, but a hand drill will work fine as well if you take pains to keep the hole straight.
Once done, thread a bolt through the holes and secure with a nut on the linoleum side. This also provides a handy way to control the thickness of the coin. If a thicker coin is desired, you can add washers or another nut to add thickness. For thinner coins, you will have to find a thinner nut.
Operations: Roll out your clay thicker than the final coin thickness. Cut out rounds with your biscuit cutter and lay on the base block (the one with the bolts). Place the top block onto the registration bolts and hand press together. Place the sandwich on the floor and tap the top block with a rubber mallet until the top block comes to rest on the stops of the base block (the nuts). Gently pry apart the blocks. You will find that the clay has spread out larger than the desired diameter. Gently peel these away from the mold and place flat on a work surface. Again with your biscuit cutter, cut the coins to the final size. Lay your coins out to dry as flat as possible without disturbing the design. If you own a dehydrator, the whole process can be sped up tremendously.
These "Star Wars" themed coins were produced in honor of Carrie Fisher to give to grieving fans (to include myself). The Death Star graphic translated to the clay belongs to Jonas Nullens aka 'Jones.' He is a Graphic & Web designer interested in Icon design, UI, App design, Illustration, Stationary, editorial design. You can see more of his work here: Jonas Nullens.
Step 11: Update #2 - a Little Clarification on Technique
Some folks have had some questions I'd thought I would address. The actual embossing technique seems to confuse some people, so I made this video on that. The series I was working on was "Protective Masks of my youth." Who does not like protective masks???
Another Instructabler wants to use a CNC to make the stamp cut out of a block of aluminum. Great idea! The CNC will be able to give you a much more detailed coin at the end and can more finely control the depth of the design. Theoretically, you could do depth with the linoleum, but I'm not that skilled. I've read that there is double thickness linoleum that might make this easier, but I have not experimented with this as of yet.
I'll continue to update this Instructable as long as I have any insight into the technique.....or until I get a CNC router!
Step 12: Update #3 - Upping My Game
It has been a while since I've updated this Instructable, so I thought I'd share my insights into this ongoing project.
1. I originally saw these coins as something I would hand out to people I met. However, that involved a lot of interaction with other humans...not my best skill. So, I just started leaving them where people could find them and take if they wanted. It pleased me to add a little mystery to people's lives even though I would never know. Since no thought in this world is original, this artist has been doing this sort of thing for decades!
2. On the technical side, I finally pulled the trigger on a tabletop furnace that can easily reach the temperatures required to fully mature the low fire clay body into ceramic and opened my eyes to the wonderful world of (low fired) glazes. The addition of the furnace added more complexity as well. Instead of a simple pit firing, I had to figure out the world of temperature ramps and soaks. The controller on the furnace is not very intuitive, but you can actually figure it out with the help of online videos. I'm of two minds about this innovation:
Pros - Makes the coins fully matured ceramic increasing their strength and with glazing increases their intrinsic value. Given the exact temperature control, I've decreased my loss rate from 10~20% to zero decreasing time lost and frustration.
Cons - The loss of the differential coloration intrinsic to pit firing. I've tried pit firing after bisque firing, but the coins just look dirty. Adds time since the ramping and soaking schedule is slow and requires a bisque firing and a glaze firing (assuming you will glaze). The glaze has to be done in smaller batches since the pieces can't touch or they will be fused together. The furnace isn't cheap. This model with the temperature controller was $550. Maybe less if you find it on the second-hand market.
Step 13: Update #4 - the Geocaching Project
I decided to do a dog-themed geocache project where the take away would be a dog-themed coin. Instead of a generic dog, I decided to make a variety of breeds to you could leave with a coin that best resembles your dog.
There was nothing different with the technique except for the scale. I had 24 different breeds using 11X17 mounted linoleum blocks. I think that this is probably the maximum size to go with since I ran into some problems. With smaller blocks, a rubber mallet was sufficient for impressing the design into the clay. However, on this scale, I had to jump up and down on the block "sandwich" to get a good impression. Luckily, I mounted the linoleum on 3/4 inch MDF and it was able to survive my jumping up and down on it.