Silicon monoxide is a material that is used extensively in the glass and metallurgical industries. In addition, silicon monoxide is also particularly important to the field of astrophysics where it is theorized to play a vital role in the production of metal silicate dust grains in the condensing outflows of dying stars. In this work, the evaporation coefficients and vapor pressure of commercially available amorphous silicon monoxide were measured over the temperature range (1301 to 1519) K using a Knudsen effusion cell and a commercial, thermogravimetric balance. A second- and third-law analysis of the vapor pressure data yielded (351 +/- 11) and (359.1 +/- 2.0) kJ.mol(-1) for the enthalpy of the vaporization reaction at 298.15 K, respectively. It is also shown that a thermodynamic assessment of silicon monoxide vapor pressure that has been used in the modeling of astrophysical condensation at 1000 K and below greatly overpredicts silicon monoxide vapor pressure.