This is how I made a form for making clay crucibles so I could contain some of the (awesome) higher temperature metals without melting my crucibles.
So you made yourself a refractory and melted every piece of aluminum you could find. But that wasn’t enough for you. Not you, you wanted more.
So you grabbed some scrap copper you found lying about and threw that in your cut down fire extinguisher or the small cast iron pot you took out of the kitchen when no one was looking. Hey it was dusty and way at the back of the cupboard. No one will ever miss it. I know that’s what you were thinking. Maybe you even went to the store and got something that was supposed to hold up to the higher temperatures required for copper or silver or whatever metal you were trying. I’m not here to judge. I did some of these things too.
BUT then you found out the hard way that cast iron melts a little too close to the same temperature as copper and the refractory you made was almost too awesome (how can anything fire be too awesome, it can’t!) and gets your temperatures up there pretty fast. Then after melting cast iron by accident you tried some other forms of metal crucibles. But you have a really hard time getting the refractory to just the right temperature without going over (It’s just sooo awesome to watch it work) so you melted through those things too. This Instructable is for you!
If I have to tell you to be safe because you could melt you face off and look like Darth Vader without the cool suite perhaps you should just read about how to do this and not try it. Safety Middle.
Step 1: Parts for the Form
I know you would rather be burning (or melting) stuff right now but we need a few parts so we can get started.
2 - 2inch pvc union
1 - 2inch to 1 ¼ inch pvc adapter piece
2ish feet of 2inch pipe ( I used the black stuff )
2ish feet of 1 ¼ pipe ( I used the black stuff )
Small bit of cardboard
1/4x20 bolt ( or similar )
Small container of Bondo
Plastic shopping bag (optional)
Tools that would be handy to have.
Hot glue gun with glue
Some sort of cutting tool
A helper if you can find an accomplice.
Step 2: Build the Base
If you slide the 2 inch to 1 ¼ adjuster piece inside of the 2 inch coupler you will notice that your crucible will not be very deep and it’s going to have a hard to deal with line in it.
You may also notice that they can no longer be separated. Don’t push them so hard… for now.
We want our crucible to have a little more depth so take one of the 2 inch couplers and cut a short collar from it. Sand your new collar and the 2 inch to 1 ¼ inch adjuster so you’re newly cut collar slides on easy and all the way to the bottom. You will want the collar to be as straight as possible so you may have to sand the cut edge a little too.
Step 3: Outer and Inner Walls
Take your second 2 inch coupler and sand the heck out of it so you can get rid of the pesky line in the middle.
Once that slides down the 2 inch pipe pretty smoothly you have sanded it enough.
Now take your base piece and slide the piece of 1 ¼ pipe into it until it has reached the bottom.
It should be a very tight fit and will probably not need any glue to hold.
Step 4: Trimming
Slide your outer wall piece onto the base.
You will notice the 1 ¼ pipe is way too long. Make a mark on the 1 ¼ pipe about ¾ of an inch to an inch down from the lip of the outer wall piece.
You will want to have a base on your crucible that is roughly the same thickness as the sides so you will want to take that into account.
Now that you have it marked cut it as straight as you can. I just used a hack saw and sanded it a little to clean it up.
Step 5: Ah the Smell of Bondo
We need a really firm end cap on the inner piece for when we are packing in our crucible material.
Bondo mixes up fast dries fast and sets up strong.
Take some cardboard and curl it up so you can fit it tightly into the bottom of the inner wall. This will keep the Bondo from going out the bottom.
Take some tape and form a wall close to the height you want the Bondo to be, plus a little for slop.
Mix up your Bondo following the instructions.
Pour it in and let it setup.
Step 6: The Rammer!
While you are waiting on the Bondo to setup it’s a good time to work on the rammer for packing your crucible.
Cut off a piece from the 2 inch pipe roughly 8 to 9 inches long.
Take some sand paper and run it around the outside of your pipe to make it so it can easily slide into the outer wall piece.
Turn your 2 inch pipe piece on end and cut it down the middle to roughly a little more than the depth of the crucible mold.
When you use the rammer it can close a little to slide into the form a little better.
Also you don’t usually need to hammer the rammer unless your clay mix is too dry. Usually hand pressure is enough.
Step 7: Trimming and Sanding and Drilling and Hot Glue
Once the Bondo has set remove the tape.
Remove the cardboard from the bottom.
Have your accomplice trim the bits of extra Bondo and sand it up nice. This will become the inner part of the bottom of your crucible. Try to keep it even and round it off a bit to help with release of the crucible from the mold.
Speaking of releasing the crucible from the mold we need a way to allow a little air to enter as we try to remove it. Drill an appropriate sized hole for the bolt you are using.
I drilled a ¼ inch hole to accommodate a 1/4x20 bolt. If your bolt was as long as mine you will need to thread it through the hole and trim it. Try to make it nice and flat on the end and keep the threads as nice as you can so you don’t tear up the Bondo as you remove it.
I also ran a small bead of hot glue around the inner lip where the 1 ¼ inch pipe meets the base.
This helps to make a softer edge on the top lip of the crucible.
Step 8: Make a Crucible!
The mold is finally ready!
Grab your favorite clay crucible recipe, mix it up and pack it into the mold.
You will want to load this mold in steps.
Some clay, then ram, then clay, then ram until you get to the end and pack the entire back with clay.
Remove the threaded bolt to allow air into the mold near the bottom of the crucible.
Wiggle the center piece side to side a little until it releases.
Flip the mold over and use the rammer to gently slide out your crucible.
It will be helpful to put a little petroleum jelly on the mold to assist with release.
I also found it helpful to put a plastic bag over the inner piece of the mold but you have to do a little cleanup with your finger on the inside of the crucible if you do that.