text: Sodium chloride is the most commonly chosen space-holder for titanium foams because it is highly soluble in water and inert with respect to titanium. This inertness prevents contamination and degradation of the mechanical properties of the resulting foam. Moreover, NaCl is non-toxic; any residuals are bioinert.
  Bansiddhi & Dunand pioneered the use of NaCl as a permanent space-holder for the fabrication of NiTi foams. The resulting foams consisted of 32-36% porosity with more complete densification than they observed when producing NiTi foams using a sodium fluoride (NaF) space-holder. However, processing parameters resulted in molten NaCl and a metal/salt blend in the cavities of the foam. Certain risks are associated with using a molten space-holder including reaction with the metal, dissolving of the space-holder in the metal and prevention of densification through the creation of a thin layer of liquid between the metal and particles. Near complete densification was achieved when NaCl was used as a permanent space-holder in pure titanium foam. In this case, a temperature below the melting point of NaCl was used; titanium is less creep resistant than NiTi, which allows for densification at lower temperatures. The resulting foams achieved porosity of 50–67% with minimal observable microporosity. Anisotropic pore shape in some areas alluded to NaCl's deformation during HIP, which is desirable for some applications. Additionally, an observed, rough inner surface of the pores holds advantages for biomedical implant applications. 
  Jha et al. achieved 65-80% porosity through the use of NaCl as a space-holder and a cold compaction process at various pressures with two-stage sintering. In this case, NaCl was removed through dissolution after the second stage of sintering. Resulting Youngs moduli (8–15 GPa) were considerably lower than the Youngs modulus of 29 GPa achieved for 50% porosity foams. This illustrates the known relationship between porosity and Youngs modulus wherein Youngs modulus decreases linearly with increasing porosity. Achievable porosity through the space-holder method is directly related to the type and amount of space-holder utilized (up to a threshold maximum achievable porosity level).