PDA

View Full Version : Home-made Crucible



zoas23
08-16-2015, 10:00 AM
Hi!

I am back here after a hiatus of some months (26 months if I am not wrong, but I could be wrong).

Many things have happened during this time. Most of them are good. The most important one for me is a woman I've met, who is currently my girlfriend and some day she'll be my wife.

I am glad that the forum is still here (very glad actually), I am glad that the old names are still around (without caring if you remember me or not, I love this place).

I wanted to ask if somebody has created a home-made crucible.
My only problem with the industrial ones is limited to a single issue: size.
The ones available in my country are either too small or too big (I use the ones which are "too small").
Importing a crucible is not an option because this Country is very much like hell when it comes to importing things.

The maximum heat I use is 1,300 C.

I have talked with persons who are into "ceramics" of different types... but, none of them has much experience with crucibles... and with persons who are into "metallurgy" of different types, but they often don't have much experience with "ceramics".

I am testing different combinations of:
-Clay (powdered)
-Chinese Talc (Silicon dioxide)
-Graphite (pure and powdered)
-Powdered refractory brick
-water

I've tested different combinations... I did not have much success.
I've noticed that the ones without much graphite aren't really heat resistant... whilst the ones with too much graphite are heat resistant but they don't really arrive to their first experience at the oven in one piece (they break before being baked... because graphite does not really have the properties of clay, it doesn't become a cement-like substance)

This is far from being "alchemy" :D ... but maybe someone here has created a home-made crucible.

I have failed many times whilst creating it, but I can't deny the fact that it is quite fun.

Other than that, hello everyone... I missed this place.

JDP
08-17-2015, 04:15 AM
Hi!

I am back here after a hiatus of some months (26 months if I am not wrong, but I could be wrong).

Many things have happened during this time. Most of them are good. The most important one for me is a woman I've met, who is currently my girlfriend and some day she'll be my wife.

I am glad that the forum is still here (very glad actually), I am glad that the old names are still around (without caring if you remember me or not, I love this place).

I wanted to ask if somebody has created a home-made crucible.
My only problem with the industrial ones is limited to a single issue: size.
The ones available in my country are either too small or too big (I use the ones which are "too small").
Importing a crucible is not an option because this Country is very much like hell when it comes to importing things.

The maximum heat I use is 1,300 C.

I have talked with persons who are into "ceramics" of different types... but, none of them has much experience with crucibles... and with persons who are into "metallurgy" of different types, but they often don't have much experience with "ceramics".

I am testing different combinations of:
-Clay (powdered)
-Chinese Talc (Silicon dioxide)
-Graphite (pure and powdered)
-Powdered refractory brick
-water

I've tested different combinations... I did not have much success.
I've noticed that the ones without much graphite aren't really heat resistant... whilst the ones with too much graphite are heat resistant but they don't really arrive to their first experience at the oven in one piece (they break before being baked... because graphite does not really have the properties of clay, it doesn't become a cement-like substance)

This is far from being "alchemy" :D ... but maybe someone here has created a home-made crucible.

I have failed many times whilst creating it, but I can't deny the fact that it is quite fun.

Other than that, hello everyone... I missed this place.

I have made my own crucibles many times, using wet clays pressed into molds and also as liquid "slip" for casting in plaster molds (which sometimes I make myself as well.) I too was limited by what is available from commercial suppliers, but since some of the experiments I perform require somewhat modified crucible shapes, and also more resistance to certain types of substances which make short-work of more conventional clays, and modern industry does not readily provide a solution at an affordable rate (for example, some companies are willing to make a crucible of your own design just for you, but you need to first make a contract with them to buy THOUSANDS of pieces, otherwise they simply do not consider it profitable to go through the trouble of manufacturing a special piece), I was pretty much forced to have to learn how to make custom made crucibles myself.

You will need:

1- Clays (there are many types, but for the type of work we are concerned with you want them to be high-fire clays, like porcelains or stonewares), either in wet malleable form for pressing or liquid "slip" for casting

2- Molds where to press or pour the clay

3- A kiln where to fire the finished dry pieces

zoas23
08-17-2015, 04:47 AM
Thank you. I have some experience with molds because I worked with them for artistic project a few times.

A simple porcelain in a mold will do the trick? The person who sells porcelain told me that it would not, but he's not an expert in crucibles, but a chemist who works at the clay store and who is called "the technician" by the other employees.

I have a klin. I will try with simple porcelain and a few other combinations using porcelain.

I will shoot a few pictures, if I end up with something useful, I'll upload them here.

JDP
08-17-2015, 01:27 PM
Thank you. I have some experience with molds because I worked with them for artistic project a few times.

A simple porcelain in a mold will do the trick? The person who sells porcelain told me that it would not, but he's not an expert in crucibles, but a chemist who works at the clay store and who is called "the technician" by the other employees.

I have a klin. I will try with simple porcelain and a few other combinations using porcelain.

I will shoot a few pictures, if I end up with something useful, I'll upload them here.

I have used several types of porcelain very successfully for some purposes (they are not good for melting lead and copper oxides, for example, as they are quickly corroded by these). Currently I use "Toshi" type porcelain made by the Laguna Clay Company in California:

http://www.lagunaclay.com/clays/slips/wc829g.php

I find it very easily at local ceramic suppliers in the form of liquid "slip" ready to be poured into plaster molds. It gives a good solid porcelain that is fairly resistant to thermal shock (but would not recommend to heat it directly over a Bunsen burner. These types of commercial porcelain work well for heating inside furnaces. For heating directly over a Bunsen burner you need special porcelains that are very resistant to thermal shock and localized heating, the so-called chemical porcelain, like the one manufactured by Coors)

zoas23
08-27-2015, 02:39 AM
Thank you,

I went to the shop and bought everything I need + a few other things you did not mention, but the shop owner suggested.

I can't do it right now because I don't have the time, but I'll give it a try next week.

I promise to take photos of all the process, for it may be useful for somebody else in the future (if I have a good result, of course).

Thanks a lot for all your good tips, JDP, I appreciate them.