Hi Herbamatic:
Fire assays are almost exclusively done with fire clay crucibles. Fire clay is composed of alumina, silica, and other refractory materials.
Different grades of crucibles are available. If you are planning on only using crucibles once, you can use a less expensive crucible:
http://www.lmine.com/category/economy_repacks.html
You can usually achieve a lower "cost per fire" by using a higher quality crucible:
http://www.lmine.com/category/ap_green_repack.html
Porcelain and other types of crucibles are not generally suitable for fire assay.
Fire assays are almost exclusively done with fire clay crucibles. Fire clay is composed of alumina, silica, and other refractory materials.
Different grades of crucibles are available. If you are planning on only using crucibles once, you can use a less expensive crucible:
http://www.lmine.com/category/economy_repacks.html
You can usually achieve a lower "cost per fire" by using a higher quality crucible:
http://www.lmine.com/category/ap_green_repack.html
Porcelain and other types of crucibles are not generally suitable for fire assay.
J
I have been using the AP Green brand exclusively for over 20 years. Over all they have been extreemly reliable and worth the small extra cost. I make money running fire assays, not repairing furnaces.
This year, I did have to send back a few cases of 20g crucibles due to manufacture cracks. Considering I have used over one thousand cases in my assay career, sending back 2 cases is a fantastic ratio. Legend Inc. was more then happy to replace them and pay for shipping.
Cant say enough about the customer service the ladies provide at Legend Inc.
This year, I did have to send back a few cases of 20g crucibles due to manufacture cracks. Considering I have used over one thousand cases in my assay career, sending back 2 cases is a fantastic ratio. Legend Inc. was more then happy to replace them and pay for shipping.
Cant say enough about the customer service the ladies provide at Legend Inc.
Hi Herb:
Fire clay crucibles are used almost exclusively for the lead collection. They hold up well to the fluxes and molten metal, and are relatively inexpensive. There are various grades of crucibles, and will typically last for 3 to 6 uses. There are many sizes, which can be seen here (the are the AP Green brand, but there are several others):
[/url]www.lmine.com/category/ap_green_repack.html[/img]
The life will be less if you are not fluxing properly. For instance, if your flux is silica deficient, your melt will be too basic, your slag may be chalky, and have entrained lead. Silica will be robbed out of the crucible which will shorten the life. The fire assay text by Shepard & Dietrich is probably the best for understanding all the complexities of fluxing:
http://www.lmine.com/product/17202A.html
You will learn to "read" the slag with practice, and can then make adjustments to your fluxing which will both improve your results but will also extend the life of your crucibles.
Fire clay crucibles are used almost exclusively for the lead collection. They hold up well to the fluxes and molten metal, and are relatively inexpensive. There are various grades of crucibles, and will typically last for 3 to 6 uses. There are many sizes, which can be seen here (the are the AP Green brand, but there are several others):
[/url]www.lmine.com/category/ap_green_repack.html[/img]
The life will be less if you are not fluxing properly. For instance, if your flux is silica deficient, your melt will be too basic, your slag may be chalky, and have entrained lead. Silica will be robbed out of the crucible which will shorten the life. The fire assay text by Shepard & Dietrich is probably the best for understanding all the complexities of fluxing:
http://www.lmine.com/product/17202A.html
You will learn to "read" the slag with practice, and can then make adjustments to your fluxing which will both improve your results but will also extend the life of your crucibles.