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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Crucible | 2/3 | https://en.wikipedia.org/wiki/Crucible | reference | science, encyclopedia | 2026-05-05T10:04:04.364838+00:00 | kb-cron |
=== Medieval period === Smelting and melting of copper and its alloys such as leaded bronze was done in crucibles similar to those of the Roman period which have thinner walls and flat bases to sit within the furnaces. The technology for this type of smelting started to change at the end of the medieval period with the introduction of new tempering material for the ceramic crucibles. Some of these copper alloy crucibles were used in the making of bells. Bell foundry crucibles had to be larger at about 60 cm. These later medieval crucibles were a more mass-produced product. The cementation process, which was lost from the end of the Roman to the early medieval period, continued in the same way with brass. Brass production increased during the medieval period due to a better understanding of the technology behind it. Furthermore, the process for carrying out cementation for brass did not change greatly until the 19th century. However, during this period a vast and highly important technological innovation happened using the cementation process, the production of crucible steel. Steel production using iron and carbon works similarly to brass, with the iron metal being mixed with carbon to produce steel. The first examples of cementation steel are wootz steel from India, where the crucibles were filled with good quality low-carbon wrought iron and carbon in the form of organics such as leaves, wood, etc. However, no charcoal was used within the crucible. These early crucibles would only produce a small amount of steel as they would have to be broken once the process has finished. By the late medieval period, steel production had moved from India to modern-day Uzbekistan, where new materials were being used in the production of steel crucibles; for example, Mullite crucibles were introduced. These were sandy clay crucibles which had been formed around a fabric tube. These crucibles were used in the same way as other cementation vessels but with a hole in the top of the vessel to allow pressure to escape.
=== Post-medieval === At the end of the medieval era and into the post-medieval era, new types of crucible designs and processes started. Smelting and melting crucibles types started to become more limited in designs which are produced by a few specialists. The main types used during the post-medieval period are the Hessian crucibles which were made in the Hesse region in Germany. These are triangular vessels made on a wheel or within a mold using high alumina clay and tempered with pure quartz sand. Furthermore, another specialized crucible which was made at the same time was that of a graphite crucible from southern Germany. These had a very similar design to that of the triangular crucibles from Hesse but they also occur in conical forms. These crucibles were traded all across Europe and the New World. The refining of methods during the medieval and post-medieval periods led to the invention of the cupel which resembles a small egg cup, made of ceramic or bone ash which was used to separate base metals from noble metals. This process is known as cupellation. Cupellation started long before the post-medieval period; however, the first vessels made to carry out this process started in the 16th century. Another vessel used for the same process is a scorifier, which is similar to a cupel but slightly larger and removes the lead and leaves the noble metals behind. Cupels and scorifiers were mass-produced as after each reduction the vessels would have absorbed all of the lead and become fully saturated. These vessels were also used in the process of metallurgical assay where the noble metals are removed from a coin or a weight of metal to determine the amount of the noble metals within the object.
== Modern-day uses ==
Crucibles are used in the laboratory to contain chemical compounds when they are heated to extremely high temperatures. Crucibles are available in several sizes and typically come with a correspondingly-sized lid. When heated over a flame, the crucible is often held inside a pipeclay triangle which itself is held on top of a tripod. Crucibles and their covers are made of heat-resistant materials, usually porcelain, alumina or an inert metal. Ceramics such as alumina, zirconia, and especially magnesia will tolerate the highest temperatures. However, chemical reactions with the material in the crucible must be kept in mind; the emergence of melting point-lowering eutectic systems is an especially important consideration. More recently, metals such as nickel and zirconium have been used. The lids are typically loose-fitting in order to allow gases to escape during the heating of a sample inside. Crucibles and their lids can come in high form and low form shapes and in various sizes, but rather small 10 to 15 ml size porcelain crucibles are commonly used for gravimetric chemical analysis. These smaller crucibles and their covers made of porcelain are quite cheap when sold in large quantities to laboratories, and the crucibles are sometimes disposed of after use in precise quantitative chemical analysis. There is usually a large mark-up when they are sold individually in hobby shops.
=== Chemical analysis usage ===