You can't turn copper blue with heat alone. Copper doesn't change color to blue when heated. Here's why:

* Copper Oxide: Copper oxide forms on the surface of copper when it's exposed to air and heat. This oxide is a black, powdery substance.

* Copper Carbonate: If copper is heated in the presence of carbon dioxide and water, a green patina (copper carbonate) will form.

To get a blue color, you need a chemical reaction:

1. Patina: You can create a blue-green patina on copper by exposing it to a solution of vinegar, salt, and hydrogen peroxide. This process creates a layer of copper carbonate, which is blue-green.

2. Copper Sulfate: Treating copper with a solution of copper sulfate will create a blue-green coating of copper sulfate on the surface.

Important Note: The blue color on copper is often the result of a patina or coating. The copper itself doesn't turn blue due to heat.