Clay Crucible Recipes





Introduction: Clay Crucible Recipes

This instructable is a few recipes for clay crucibles, getting them ready to melt metals and lots of pictures of things that didn’t quite work out for me. But hey, it was fun.

I have successfully melted Aluminum, Copper, Silver and various bits of mixed metals with these recipes.

Step 1: Recipe Number 1

Straight to it.

You’re going to need fire clay and silica sand.

300 grams silica sand.

200 grams fire clay.

Fire clay can be found at most places that sell concrete and cinder blocks. I got my fire clay and silica sand at BASALITE. They were really nice and the stuff is cheap.

A 50 pound bag of fire clay was $12.80 and a 100 pound bag of 70 mesh silica sand was $8.52 not bad huh!!!

You can make a lot of crucibles with that much material.

Mix the sand and clay together (dry).

Slowly mix in water until it holds its shape when squished in your hand. This took me some practice to get it just right.

Form the crucible using your favorite technique.

I used a mold.

Let your crucible dry.

Step 2: Cooking Recipe Number 1 Crucible

After your crucible has dried you will need to cook it before you use it.

This will help to burn off all the stuff in the clay that can contaminate the metal you may be melting and it will set the clay to make the crucible stronger.

I used a simple charcoal setup for this.

Get some charcoal, a chimney starter, a bit of dryer duct and a hair dryer to cook your crucible.

Place the charcoal in the bottom of the chimney starter.

Place the crucible in the middle of the chimney starter. Fill the rest of the chimney starter with charcoal. Place it on something so you can fit the dryer duct under it.

Start the coals.

Once they are glowing red hot you can put the dryer duct in place and start the hair dryer on low. Let it run until the coals have burned down about half way and add a few more on top.

Run the hair dryer for about an hour longer then let the whole thing cool in place over night.

If everything went well you should have a crucible that sounds kind of like a coffee cup when you flick it with your finger.

If it has any cracks it will fail if you use it. So don't use it.

Step 3: Recipe Number 2

You should be able to get all of these items at most pottery stores.

I picked mine up at Potters Center.

10 grams Alumina Oxide.

40 grams Feldspar.

75 grams Kyanite.

75 grams Kaolin clay.

75 grams Calcined Kaolin Clay.

300 grams Silica Sand.

Mix everything together dry.

Mix in water slowly until it just holds its shape when you squish it in your hand.

Form the crucible using your favorite technique.

Let your crucible dry.

Step 4: Recipe Number 3

10 grams Aluma Oxide

40 grams Feldspar

75 grams Kyanite

75 grams Kaolin

300 grams Silica Sand

Mix everything together (dry).

Mix in water slowly until it just holds its shape when you squish it in your hand.

Form the crucible using your favorite technique.

Let your crucible dry.

Step 5: Recipe Number 5

10 grams Aluma Oxide

55 grams Feldspar

75 grams Kyanite

60 grams Kaolin

300 grams Silica Sand

Mix everything together (dry).

Mix in water slowly until it just holds its shape when you squish it in your hand.

Form the crucible using your favorite technique.

Let your crucible dry.

Step 6: Recipe Number 6

100 grams Kaolin

300 grams Kyanite

Mix everything together (dry).

Mix in water slowly until it just holds its shape when you squish it in your hand.

Form the crucible using your favorite technique.

Let your crucible dry.

Step 7: Cooking Crucibles

I tried cooking recipe 2 and 3 with the charcoal method but found they didn’t get hot enough to develop much strength. The first time I tried using them they broke from the force of the Borax expanding inside of them.

This can be a bit annoying especially since it takes some time to get them ready.

So I changed the cooking of recipe 2 through 6 with extremely improved results. If you have access to a kiln you’re all set if not you can make one real quick with some fire bricks.

They need to be cooked in a kiln or some form of kiln to around 2300 degrees Ferenhight and held near that temperature for around 45 minutes to an hour. This may sound like a bit of a tough thing to do if you don’t have a kiln however it’s really not that bad.

Once they have cooled they will sound like a coffee cup when you flick it with your finger?

Now fire up your refractory.

Get your crucible a little warmed up before you put it into the refractory by placing it on some hot coals.

Melt the heck out of some metal !

So far my favorite recipe is number 6.

Clay crucibles can handle the heat but you do have to treat them a little different then a metal crucible.

Temperature shock is a problem for clay.

It seems to be pretty easy to address by simply setting the crucible on or in some hot coals after use so it can cool slowly.

If a crucible cracks you will want to stop using it.

You don’t want a crucible full of lava spilling all over you, do you?!?

Step 8: Lots of Cool Pictures

These are a bunch of extra pictures.



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    Hi quick question I am trying to make a mix since we have limited supplies here in my country so I would like to ask how 50% plaster of paris with 12.5% grounded flower pot, 12.5% ash, 12.5% sand and 12.5% grounded brick any input is appreciated thank you

    The crucible in the pictures look to be 1/4" thick and the size of coffee cup . If I needed to do a much larger crucible 8 to 10 inches tall and 6 inches wide , should I make the crucible a 1/2" thick ? I'm wanting to make bar stock to make swords and other custom items . I've gotten a hold of about 200 lbs of stainless . How do you feel these crucibles will hold up ?

    Oh and thanks a lot .... people like you help idiots like me have fun .

    4 replies

    stainless steel is also hazordus to heat up it produces chromium hexavalent so ware ppe if you plan to heat up stainless

    Just so you know stainless steel is horrible to make swords

    I'm not sure how heavily you plan to load the crucibal but you might even go the 3/4" thich. You gain strength but trade off how fast the crucibal can heat up. You'll also want to cool the crucibal slowly so it's not as likely to crack.

    poodydad0101, they are about 1/4" thick 2 1/2" tall and 2 1/4" across. I would go to 1/2" thick for a bigger one like you describe. I have not tried to melt stainless steel yet but most of what I have found says it melts around 2550 F. The fire clay should hold up to that without much trouble but there is a bunch of gunk in it that may contaminate your stainless a bit. If you find the fire clay crucibles adding some gunk try one with the kaolin, it is more clean. I'm going to look around for some stainless now just to give it a try. Keep me posted on your results. Fire = Fun :) Be safe.

    Have you compared the effectiveness of these crucibles to commercial grade crucibles?

    How long do you let them dry before firing them?

    I mould the sand / clay mix around the outside of a polystyrene (Styrofoam) cup, then allow to dry for a few days. When set, just run your propane torch around the inside to burn off the polystyrene. You get a nice smooth inner surface.

    hi, i was just wondering if i can use them in a microwave...

    Hey I was wondering if u needed a 70 mesh silica for a specific reason or can I use 50 mesh??

    thanks for the advice, i was also wondering how you went about making the mold to get your nice shape.

    1 reply

    I have another instructable for how I made my mold. Search for how to make a crucible mold. If you use it post some pics of your results.

    what types of molten metal can number 1 withstand, I'm starting out but need something that I can remake when my crucible breaks

    1 reply

    I have melted aluminum, copper and silver in recipe number 1. be sure to put some Borax on top of the copper and silver to cut down on oxidation. The crucibal that get cooked in the kiln has a higher physical strength so if you cook it with briquettes, handle them carefully. They get stronger with use. Also be sure to cool them slowly in your refractory or in some hot briquettes. That should help them to last longer.

    I used 48 mesh.

    I've been trying for months to find a place that sell fire clay, but I can't seem to find anywhere in my state that sells it. Any advice? I need it both for crucibles and to make a decent foundry lining.

    2 replies

    I found mine at brick and stone supplier


    Have you tried any places that do work on fire places. I actually called a fireplace repair shop when I first started looking for fire clay. They directed me to Basalite. I'm sure a local shop could do the same for you. There is always Ebay too. The link to Ebay isn't the exact same as my bag but I bet it's similar enough :)