How to Anneal Copper

Annealing copper makes it softer and more malleable, allowing for easy bending. This process enables you to shape the metal without breaking it. You can anneal any grade and thickness of copper if you have a powerful enough torch. The simplest way to anneal copper is to heat it with an oxy-acetylene torch and then quickly cool it in water.

Preparing for Annealing

Step 1. Wear protective goggles before working with the torch.

Wear protective goggles before working with the torch. When dealing with an open flame, it is essential to use protective goggles. Use goggles with a shade rating of at least 4 to adequately protect your eyes from the bright light of the acetylene flame. Looking at the flame of an acetylene torch without protective goggles can seriously damage your eyes.

• Goggles used for annealing, arc cutting, and welding are rated on a scale from 2 to 14, where 2 is the least tinted and 14 is the darkest lenses. The acetylene torch produces a much less bright flame than a welding torch, so lightly tinted glasses are sufficient for eye protection.
• If you don’t have protective goggles, you can buy them at a hardware or welding supply store.

Step 2. Connect one hose to each cylinder.

Connect one hose to each cylinder to prepare the acetylene torch. The torch, which releases the flame, has two hoses coming out of it. Connect the red hose of the torch to the acetylene cylinder and the black hose to the oxygen cylinder. Acetylene ignites the flame, and oxygen will continue to fuel it. By adjusting the amount of oxygen flowing from the cylinder, you can control the flame's intensity.

• First, make sure that the two gauges on the oxygen cylinder and both gauges on the acetylene cylinder are set to "0".[2] X Source
• If you don’t have an oxy-acetylene torch, you can purchase or rent one from a hardware or building supply store.

Step 3. Turn the acetylene valve a quarter turn clockwise.

Turn the acetylene valve a quarter turn clockwise. This will open the acetylene cylinder, allowing gas to flow into the regulator. Turning the valve just a quarter turn is sufficient for the acetylene to maintain the flame without overwhelming the flow, which allows you to control it. Watch the gauge and adjust the valve to achieve a pressure of 0.5 atmospheres.

• The gauge is located on top of the acetylene cylinder. It has a circular scale marked with "pressure" and "atm".
• Once the flame is established, you can adjust its intensity using the valve on the acetylene cylinder. The valve is typically located at the top of the cylinder, often near the gauge (or even connected to it).

Step 4. Fully open the oxygen valve counterclockwise.

Fully open the oxygen valve on the oxygen cylinder counterclockwise. Then, adjust the pressure using the screw on the regulator (turn it clockwise). Keep an eye on the gauge on the oxygen cylinder — aim for a reading of 2.7 atmospheres.

• The oxygen valve is located at the top of the oxygen cylinder. It may have an arrow indicating the direction to turn the valve.
• It is crucial to achieve the correct ratio of oxygen to acetylene for a controllable hot flame.

Step 5. Ignite the acetylene torch with a flint lighter.

Ignite the acetylene torch using a flint lighter. To light the flame, hold the torch in one hand and turn the valve on top of the acetylene cylinder half a turn clockwise with the other hand. This will allow gas to flow into the torch. Bring the flint lighter to the torch nozzle about 1.5 centimeters away. Click it until an orange-red flame appears.

• Light the flame no later than 2-3 seconds after opening the acetylene valve, as this gas ignites easily.

Step 6. Adjust the torch valve until the flame turns blue.

Adjust the torch valve until the flame turns blue. After the torch starts producing a light orange flame, turn the oxygen valve on the side of the torch clockwise to mix oxygen with the burning acetylene. Continue turning the valve until the flame turns blue. A blue flame indicates that the temperature is perfect for annealing copper.

• Turn the oxygen valve slowly to avoid a sudden flare-up of the flame.
• A flame that is too hot will burn the metal, while a flame that is too cold will not sufficiently heat the copper, leaving its durability and malleability unchanged.

Heating the Copper

Step 1. Keep the flame 7.5–10 centimeters away from the copper surface while annealing.

Keep the flame 7.5–10 centimeters away from the copper surface while annealing. Point the flame directly at the copper sheet or pipe. Do not bring the torch too close to the metal, or you will burn its surface. Keep the torch at least 10-13 centimeters away from the copper surface and wait for the metal to heat up.

• Copper does not ignite. However, the metal should be placed on a fireproof material, such as brick or concrete.
• Anneal copper in a well-ventilated area. Harmful chemicals are released during annealing, which can enter your lungs without proper ventilation.[8] X Source

Step 2. Move the flame quickly across the metal surface.

Move the torch flame quickly across the metal surface. Sweep the torch along the entire surface to evenly heat the copper. It is essential to distribute the heat evenly throughout the metal so that some areas do not anneal faster than others. You will notice that the heated areas of the copper surface turn red or orange.

• Keep a dry chemical fire extinguisher on hand when working with an open flame. If anything ignites, use the extinguisher immediately.

Step 3. Thicker and bulkier pieces of copper should be heated longer.

Thicker and bulkier pieces of copper should be heated longer. Annealing allows any piece of copper to be softened, regardless of its thickness and size. However, the thicker the metal, the longer it should be heated.

• For example, a thin piece of jewelry copper only needs about 20 seconds of heating to be annealed. In contrast, a large copper pipe or a sheet of copper 1.5 centimeters thick should be heated for at least 2-3 minutes.

Step 4. Hold the flame in one spot until the copper glows red.

Hold the flame in one spot until the copper glows red. When heated with the acetylene torch, the surface of the copper will first turn black. Don't worry: it will then turn red. Continue to move the flame over the metal surface until the black color is replaced by a bright red glow. This color indicates that the copper has been annealed.

• Regardless of the size or thickness of the copper being annealed, it will be fully annealed once it starts glowing red.
• A cherry-red color also indicates that the copper has undergone annealing.

Cooling the Copper

Step 1. Close the torch valves.

Close the torch valves. After annealing the copper, you can extinguish the flame. Turn the acetylene valve counterclockwise to stop the gas flow. Then, close the oxygen valve. The flame should go out after this. You can now remove your protective goggles.

• First, close the acetylene flow, then the oxygen, to ensure all acetylene burns out.
• Be careful when turning off the acetylene torch, and do not point it at other people.

Step 2. Use pliers to handle the annealed copper.

Use pliers to handle the annealed copper. Immediately after annealing, the copper will be very hot, so do not touch it with bare hands. Slide the edge of the copper sheet or pipe under one jaw of the pliers, squeeze tightly, and lift the annealed piece. If you don’t have pliers, you can purchase them at a hardware store.

• At this stage (and during the annealing process), there is no need to wear gloves since you won't be touching the metal until it cools.
• If you don’t have another tool, you can pick up the hot copper with regular tweezers. Be careful not to drop the hot metal!

Step 3. Place the annealed copper in a metal bucket of water.

Place the annealed copper in a metal bucket of water. This will cause the glowing hot copper to cool immediately. Watch as the metal cools down. Once the copper returns to its usual reddish-brown color, remove it from the metal bucket using pliers.

• The cooling process should take no longer than 5 minutes. After this time, the annealed copper will become soft and malleable.
• Hot copper should be cooled in a metal bucket as a plastic bucket may melt.