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Lab Tips: How to Use and Clean Crucibles?


A crucible is a container that can withstand very high temperatures and is used to keep metals, glass, and pigment for melting in a furnace. Laboratory crucibles are designed to withstand relative high temperatures encountered in the metal casting experiments. The crucible should essentially be made of materials with a much higher melting point than that of the materials to be melted. The crucible materials should also have good strength even when extremely hot. Common laboratory crucibles include boron nitride crucible, pyrolytic boron nitride crucible, etc.

The crucible is an invaluable part of the laboratory gear, and they’re expensive as well. Once you are done conducting your experiments, you need to know how to maintain crucibles effectively and without causing damage to the crucible surface so it can be used again.

Usage Tips

Never filled the crucibles with a cold metal, such as aluminum – as there are strong chances that the metal will expand and crack the container.

The crucibles should be “tempered” before usage. Heat the empty crucible to a temperature of about 500 deg F. and hold it for 20 minutes. Then work the crucible to red heat. Turn off the heat and leave the crucible to cool slowly. This process takes off any moisture in the crucible.

Crucibles should properly be tested for cracks prior to each application. Replace the cracked crucibles with new ones.

lab crucibles

How to clean them?

Cleaning chemicals from ceramic crucibles is relatively easy. Therefore, ceramic crucibles are usually preferred for lab men. You will only need a few basic chemicals and supplies.

Step 1: Gently scrape as much residue left from the materials used in your experiment from the crucible. Therefore, ceramic crucibles are usually preferred for lab men.

Step 2: Fill your ceramic crucible with fused potassium bicarbonate (solid form). You should have enough bicarbonate in the crucible to fill past the line of the remaining material from your experiments. If you need to fill the entire crucible, do so.

Step 3: Place the crucible on a burner. Heat the crucible until the fused bicarbonate melts. Heat it until a layer of red potassium salt appears on the surface. Using a mixing rod, stir the melt a few times. The entire melting procedure should take about one minute.

Step 4: Remove your crucible from the flame. Pour out the melt.

Step 5: Rinse the crucible in hot water. Use a clean cloth to dry the surface. If your crucible is platinum, use alumina-impregnated nylon webbing to complete cleaning the surface. Let the crucible cool.

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