Goggles used for annealing, arc cutting, and welding are rated on a scale of 2–14, with 2 as the least tinted and 14 as the most tinted. Since an acetylene torch is much less bright than a welding torch, your eyes will be protected by relatively lightly tinted glasses. If you do not own a pair of safety goggles, purchase a pair at a large hardware store or a welding-supply store.
Before you begin, make sure that the 2 pressure gauges on the oxygen tank and the 2 pressure gauges on the acetylene tank are all at “0. ”[2] X Research source If you don’t already have an oxygen acetylene torch, you can purchase or rent one from a large hardware store or a home-improvement store.
You’ll find the pressure gauge directly on top of the large acetylene tank. Look for the dial that is marked “pressure” or “psi. ” Once the flame is burning consistently, you can adjust its intensity by turning the acetylene-tank valve so it’s more or less open. Find the tank valve on top of the acetylene tank. In most cases, it will be next to (or even attached to) the pressure gauge.
The oxygen-control valve will be a handle located on the top of the oxygen tank. It may have a directional arrow indicating which way is “on. ” A correct mixture of oxygen to acetylene is crucial to produce a hot, manageable flame.
Once you’ve turned on the acetylene gas knob, don’t wait more than 2–3 seconds to pick up the striker once the gas is flowing, as it’s incredibly flammable.
Turn on the flow of oxygen slowly, so the flame doesn’t suddenly flare up. A flame that is too hot will burn the copper, while a flame that is too cool will not be strong enough to change the copper’s properties like durability and malleability.
The copper won’t catch on fire. However, to avoid catching anything else in your work environment on fire, the copper should be on top of a non-flammable object like a piece of brick or concrete. Always anneal copper in a well-ventilated area. Annealing copper produces chemicals that can harm your lungs if the room you’re working in doesn’t have proper ventilation. [8] X Research source
Have a dry chemical fire extinguisher in close proximity whenever you use an open flame. If any of the materials in your garage or metalworking lab catch on fire, spray them with the fire extinguisher immediately.
For example, you may only need to heat a thin jewelry-grade piece of copper for 20 seconds to anneal it. For a heavy copper pipe or 1⁄2 in (1. 3 cm) thick chunk of copper, you’ll need to anneal for at least 2–3 minutes.
Regardless of the size or thickness of the copper you’re annealing, it will be fully annealed once it’s glowing red. Copper that is glowing cherry red is at the correct temperature for annealing purposes.
Closing the acetylene valve first and the oxygen valve second will clear the torch of any acetylene. Even when you’re turning off the acetylene torch, be careful not to point it at any other people in your workspace.
You don’t need to wear gloves at this point (or at any other point during the annealing process), since you’ll never touch the metal directly until it’s cool. In a pinch, you could use a pair of ordinary tweezers to pick up the superheated copper. Just be careful not to drop it!
The cooling process should take less than 5 minutes. Once this time has passed, the copper is now annealed and will be soft and malleable for working. It’s important that you use a metal bucket to cool the heated metal, since it could potentially melt through a plastic bucket.
