Using a gold melting machine: ten mistakes that crack crucibles and lose metal

An induction gold melting machine is easy to run: load the metal, press start, and a few minutes later it is liquid. Because it is easy, small mistakes repeat. They crack crucibles, waste metal, cause holes in castings and can even throw hot metal out of the crucible. Here are the most common ones.

1. Choosing a size your power supply cannot run

Check this before you buy. The IG-1/2 (1 and 2 kg) runs on normal single-phase 230 V power. The IG-3/4 and IG-10/20 need three-phase 440 V. Our capacity guide helps you pick the right size.

2. Using a damp crucible

Graphite crucibles soak up moisture in storage. Heat a damp one quickly and the water turns to steam inside the wall, which can crack it. Moisture also causes gas holes in castings.

• Store crucibles in a dry place, off the floor.
• One crucible maker suggests drying crucibles stored for over a week at 110 to 150 °C for two to four hours.
• Preheat slowly before the first melt of the day, as your crucible maker recommends.

3. Loading wet or dirty metal

Water on scrap, or inside a hollow piece, turns to steam the moment it meets molten metal. That can throw metal out of the crucible. Always dry the metal first. Oil, polish and solder in scrap also cause problems later, so clean scrap before melting.

4. Jamming cold metal into the crucible

Metal expands as it heats. Pieces packed tightly against the wall push on it and can crack it. Load loosely and add more metal once the first charge melts.

5. Expecting the same weight of silver as gold

Our IG machines melt both gold and silver. Like most melting machines, their capacity is rated in 24 kt gold. Silver is a little over half as heavy as gold for the same size, so a crucible that holds 2 kg of gold holds much less silver. If you mainly melt silver, ask us for the silver capacity of the model before you buy.

6. Holding the melt at full power

Once everything is liquid, extra time at full power only wears the crucible and oxidises the metal. Pour once the charge is fully melted and at the right temperature. A full charge melts in about 4 to 6 minutes on the IG-1/2, 6 to 8 minutes on the IG-3/4 and 15 to 20 minutes on the IG-10/20.

7. Ignoring the chiller

The induction coil is cooled by water from a chiller. If the chiller is off, low on water or blocked, the machine overheats. Start the chiller first and check its water level every day.

8. Using a worn crucible

Check the crucible before every melt for cracks, chips and thin walls. Replace it when you see them. Stir and skim with graphite or ceramic-coated tools, not sharp steel. Let it cool naturally, and never cool it with water.

9. Thinking melting purifies gold

Melting does not raise the karat. The other metals in the alloy stay in it. If you buy old gold, test it before you melt it, because once it is mixed you cannot tell which piece was low. A gold testing machine does that at the counter.

10. Skipping safety gear

Gold melts at over a thousand degrees Celsius. Wear a face shield or safety glasses, heat-resistant gloves and closed shoes. Keep the floor dry and keep other people back while you pour.

A simple daily routine

1. Start the chiller and check the water.
2. Inspect and preheat the crucible.
3. Load clean, dry metal loosely.
4. Melt, then pour once fully liquid.
5. Let the crucible cool naturally.

Where to see and buy it

These are the Semsons Tech machines for this job. The store links let you book online; the other links open the full specifications or a quotation request.

Want to see an induction melting machine running before you buy? Book a demonstration or call +91 98216 12340.