Non-restraining factors affecting setting expansion of phosphate-bonded investments.

Only a few studies on the setting expansion of phosphate-bonded investments have been published. In the present work the effect on the non-restrained setting expansion of mixing time, mixing liquid, mixing device, and volume mixed was investigated for selected brands of this type of investment. It was found that all variables studied may greatly affect the setting expansion, and that the use of the special liquid delivered by the manufacturers in most cases causes an unacceptably high expansion. A modification of the brands studied appears necessary before they can be employed in a precision-requiring technique.