The space-holder technique is the most commonly employed method for producing titanium foams. The space-holder technique allows for the fabrication of higher porosity foams (35–80% ) than other techniques, while also giving the engineer more control over pore fraction, shape and connectivity. Mechanical properties can be adjusted through the size, shape and quantity of space-holders employed. The space-holder technique was first demonstrated by Zhao and Sun for the fabrication of aluminum foams in a powder metallurgical method, which consisted of the incorporation of NaCl as a space-holder. The space-holder was mixed into the powder mixture and dissolved prior to sintering. The same method was used to create titanium foams for the first time when Wen et al. utilized ammonium hydrogen carbonate spacers.