Leather becomes brittle and susceptible to creases and dents when it dries out, and a fast way to remove these defects is to use an iron. The presence of such defects is a sign that the leather needs conditioning to replace some of the lost moisture. You should condition your leather furniture regularly to prevent such problems, and you should also protect it by keeping it away from heat sources that can dry it out.
The Need for Timely Treatment
When the animal was wearing the skin that is now covering your sofa or chair, its fats and natural oils were constantly lubricating the pores and fibers. These oils are replaced during the tanning process, but they eventually migrate to the surface and evaporate. To maintain the leather, therefore, you should periodically replace the oils; if you don't, the pores dry out, the fibers harden and break, and the leather cracks. Cracks are irreparable, but creases and dents are precursors to cracks, and you can repair them if you get to them in time.
Use a Clothes Iron
You can remove creases and dents with an iron. To make sure you don't burn the leather instead of repairing it, set the iron to its lowest possible setting and cover the area you want to repair with a paper bag. Set the iron on the bag and press down; then move the iron around to prevent scorching. The heat allows the brittle fibers to stretch out, and after a minute or so, the crease or dent should be gone. Repeat the procedure for each crease or dent on your piece of furniture.
Clean Before Conditioning
To prevent leather from drying out and becoming brittle, you need to condition it to replenish the moisture. Before doing that, you should clean off surface grime, or it will sink into the pores along with whatever conditioner you use. The best leather cleaners are pH-neutral cleansers such as plain water or water mixed with a small amount of mild dish soap. The alkalinity of stronger soaps and detergents can actually break down the oils you're trying to preserve and contribute to the brittleness that's causing the creasing, so avoid them.
Condition With Replenishing Oil
After wiping down the leather, the moisture will soak in, and this is actually the best time to condition the leather; the oils in the conditioner can more easily replace the ones the water is displacing. Apply a small amount of conditioner that contains mink or neatsfoot oil and rub it in until it disappears. Avoid petroleum-based conditioning products, over time, they can actually deteriorate the fibers. To prevent your furniture from drying out, it also helps to keep it out of the sun and away from heat sources such as baseboard heaters or the fireplace.