Introduction: How to Sand Cast a Deep Onion Coin
Welcome to my instructable where I will show you how for forge a coin using the sand casting method. The coin I have made is a physical version of a cryptocurrency called Deep Onion. More details about Deep Onion can be found here https://deeponion.org/ but its a very active and supportive community which welcomes people who have been around crypto for a long time or complete newbies like myself. Take a look, I don't think you will be disappointed.
As disclaimer obviously the coin I made has no real value and is for novelty purposes only, and please be careful if you try this and don't set yourself on fire! I really cannot stress the last part enough.
Step 1: Make Your Template
First up, you need a template to use in the cast. I made mine out of a circle of soft wood I had spare. To give me a guide i printed out the logo for Deep Onion and stuck it onto the coin. I then used a scalpel to carve the design into the wood. Take your time here, I rushed a little which caused a few issues later on.
For the reverse I drew on a number 1 and then carved this, my drawing skills are about as good as my 3 year old daughters so i didn't feel confident in drawing the logo on.
Step 2: Things Needed for Sand Casting
In order to make a mould you need sand a parting agent and something to hold the sand. I would suggest visiting ebay or googling for these items. The sand is oil based and the parting agents are harmful to aquatic life so please be careful when handing lease and wear gloves (I only had one glove on as I was operating the camera with the other)
Step 3: Making the Mould
Once you have everything together set your moulds out, fill the bottom half of one with the sand making sure it is pushed down, I used a piece of wood to do this, once it is level and well packed in add a bit of the parting agent and place your template in. Give it a little push down to secure and then add the top half of the mould.
Repeat with the top half making sure you squash down until it is well packed and flat.
Step 4: Removing the Template
Once you have made the mould you can part the top and the bottom half and it should leave you with an imprint on one side and the template stuck in the other, carefully remove the template. If you make a mistake at this point just start over again and re do the mould, the sand is reusable.
After you have removed the template you need to create channels for the metal to run into, this helps to ensure the cavity is completely filled. Make one at the top and three at the bottom.
Step 5: Melting the Metal
Put the mould back together and secure, I used two clamps to do this but some moulds have screws for this.
The metal I used was bismuth, this isnt an ideal metal for coins long term but I had some spare so decided to give it a go. I would recommend using pewter or silver.
Using a butane gas torch melt the metal in a fireproof bowl, I used a stainless stee bowl I had from ikea on top of a piece of stone. Be very very careful if you pour this molten metal on you it will hurt, a lot!
Step 6: Pouring the Metal
Once the metal is fully liquid pour it into the mould, I am afraid I don't have photos of this as I was making sure I didn't pour it onto my lap.
When pouring do so slowly and use something to pick up the metal dish other than your hands, I used a pair of pipe grips as this enabled me to keep my hands well away from the metal.
Step 7: Removing the Coin
Go away and make a cup of tea at this point, this will give the metal time to cool and you've earned it.
Once refreshed seperate the top and bottom mould which should reveal your coin. It wont look good at this stage but you should be able to see the design.
Cut off the excess metal and give the coin a clean up to remove any sand or parting agent the remains.
Step 8: Finishing the Coin
Once out of the mould you have the real nasty work to do, sanding and polishing, to speed up this process I used a dremel tool to do the majority and then finished with wet/dry paper.
Work the way through the grits until you have a good smooth finish on your coin.
Step 9: The Finished Coin
Here you have it the finished article, now clearly I am no master craftsmen but you get the idea of what is possible, if you have a go at doing this yourself please post your results below and I hope to see you in the Deep Onion forums.