Titanium foil is a piece of titanium sheet that has a thickness lower than 0.009 inches. If it’s ticker, it qualifies as a sheet or titanium plate rather than a foil.
Titanium metal can be pressed as thin as 0.001 inches, though there aren’t many applications that need this size. This kind of titanium sheets are produced at secondary fabricators by using either raw materials provided by the customer or using the mills own resources. Some mills will not manufacture foils from outside titanium sources without grade certification and mechanical property testing to ensure that they are outfitted with the proper equipment. Grade is a significant consideration as processing high purity titanium is extremely energy intensive and ductility varies among the many titanium grades.
As you could have guessed by now titanium foil is used in projects that are already making use of sheets made from other metals and wish to take advantage of the properties of the titanium metal, mostly its legendary corrosion resistance and lower weight, since the durability and fracture toughness are much reduced due to the intrinsic forming of the material.
One would think that the most common use for titanium as a thin foil is in shavers, as there is many a company that manufactures razors and use titanium in their marketing efforts. However, the blades of these razors are made from steel with a titanium coating, and not from titanium per se.