Re-tinning and refinishing a copper pan is essential to controlling the temperatures of foods and sauces. The tin coating on copper pots tends to wear off with use. Copper reacts with certain foods, especially those with acidic content, such as vinegars and tomatoes. Lining the pot with tin will protect the food and allow the copper to do its job as a heat conductor. You know you need to re-tin the copper pot when the copper starts going through the tin.
Rub the inside of the copper pan with steel wool until the copper is showing through the tin. It might require a bit of scrubbing before the copper becomes visible. The copper surface should be shiny and bright.
Coat the moleskin with flux and rub the moleskin over the inside of the copper pan to coat it thoroughly. Moleskin is a pad consisting of denim or cotton corduroy layers that are stitched together. Rubbing flux on the pan helps the copper to adhere once heated.
Set the pan in the hearth to start the heating process. The hearth should be set to about 232 degrees Celsius (450 degrees Fahrenheit). Let the pan heat up but don't allow it to oxidise the inside; rather focus on heating the copper from the outside of the pan. If you don't have a hearth or oven, you can used a brazing torch to heat the pan.
Apply the tinning stick when the pan gets hot and apply the molten tin with the moleskin until it is well-coated. The moleskin should be kept slippery with tallow to produce a smooth layer of molten tin. This will stop the pan from sticking and burning.
Remove pan from the hearth and allow it to cool on its own. If it cools too quickly, it may not produce an even surface.