Always use tongs that fit well when handling different types of crucibles. Using the wrong tongs can damage the crucible or even cause it to fail at the most inconvenient time.
Before heating, place a cardboard disk between the crucible and the furnace base. It will burn off, leaving a carbon layer that prevents the crucible from sticking to the furnace bottom. Alternatively, a Plumbago (Carbon Black) coating can serve the same purpose.
Use separate crucibles for each metal type to prevent contamination. Always empty the crucible after use. Leftover metal can expand when reheated and ruin the crucible.
Please temper new crucibles or those that have been stored. Warm the empty crucible for 2 hours at 220 F (104 C), ensuring proper ventilation as new crucibles will smoke while the glaze sets. Next, heat the empty crucible until it glows red. Let the crucible cool down to room temperature inside the furnace before using it. This process should be applied to ALL new crucibles and any crucible that might have been exposed to moisture while in storage.
Keep all crucibles in a dry place. Moisture can lead to cracking when heated. If stored for a long period, re-tempering is recommended.
Silicon carbide crucibles, which are least prone to water absorption during storage, usually don't require tempering before use. However, it's advisable to heat a new crucible to a red-hot temperature before its initial use to eliminate and solidify factory coatings and binders.
Ceramic crucibles, graphite crucibles and metal crucibles differ in terms of their properties and suitable applications:
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Generally, ceramic crucibles and metal crucibles have lower thermal conductivity compared to graphite crucibles. And metal crucibles typically exhibit greater thermal conductivity than ceramics. This means that ceramic crucibles may take longer to heat up and cool down.
Typically chemically inert and corrosion-resistant, ceramic crucibles are ideal for applications where potential reactions with the crucible material are a concern. While graphite is generally resistant to most chemicals, it can react with specific gases or substances, particularly at high temperatures. And depending on the metal or alloy used, metal crucibles may be susceptible to corrosion or chemical reactions with certain substances. Some metals, like stainless steel, are more corrosion-resistant than others.
Renowned for withstanding temperatures over °C, ceramic crucibles are ideal for high-heat processes such as metal casting and glass melting. However, the specific graphite type and material impurities can affect their performance. While the temperature resistance of metal crucibles depends on the specific metal or alloy used. and many metals can withstand high temperatures, they may have limitations compared to graphite in certain extreme conditions. For applications requiring extremely high temperatures, ceramic crucibles might be slightly superior.
Graphite crucibles are durable and resistant to thermal shock. However, they can be brittle and may be more susceptible to physical damage compared to metals. Also, ceramic crucibles are more prone to cracking or chipping if subjected to mechanical stress. While metals are generally more ductile and malleable, making metal crucibles more resistant to mechanical stress and physical damage.
Ceramic Crucibles are commonly used in applications requiring chemical corrosion resistance and high-temperature stability, like in the analysis of minerals, metals, and ceramics. While graphite crucibles are popular in metallurgical applications, jewelry crafting, and procedures involving high temperatures, such as metal and alloy melting. And metal crucibles are typically used in applications depending on the specific metal or alloy and requiring durability. For example, stainless steel crucibles are used in laboratory and industrial settings, while platinum crucibles may be used in high-precision applications.
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