Titanium is a hard, light, silvery metal under normal circumstances. It can be brittle at room temperature, but it becomes more pliable as temperatures rise. Titanium's excellent strength-to-weight ratio is one of its most useful properties. This means it is both extremely strong and extremely light. It can be used in many products where weight is important such as in aircraft construction and space travel. At room temperature, titanium forms a weak alloy with aluminum. This alloy is used in some commercial products. For example, the wing of an Airbus A380 is made of this material. Also at room temperature, titanium is very reactive with oxygen at higher concentrations. This makes it unsuitable for some applications that require stability or inertness. In order to use titanium in products that will be exposed to heat or other conditions that might cause damage, it must first be treated or processed into a different state. Two common processes used to change the physical properties of titanium are hot working and cold working. During hot working, titanium pieces are heated to a high temperature (800 degrees Celsius or 1472 degrees Fahrenheit) and then cooled down quickly (1,000 degrees Celsius or 1,572 degrees Fahrenheit in 2 seconds). The purpose of this process is to make the metal easier to work with. There are two types of hot working processes: welding and forging. In welding, small pieces are welded together to form larger shapes.