| What are the requirements of impregnants?
U.S. Naval Weapons Plant Navord Report #6957 states "An impregnant suitable for porous castings must be capable of penetrating and filling the casting porosity To meet this requirement successfully, the impregnant should be a polar, low viscosity liquid containing no inert solvents, no filterable solid materials in suspension and producing no gaseous or liquid byproducts on curing or transforming into an impervious solid inside the casting porosity. Polarity in the impregnant is desired to enhance its wetting property. This property enables the impregnant to penetrate the tiniest openings and the deepest recesses of the porosity by capillary action where hydraulic pressure alone may fail to accomplish this result. That is, such an impregnant can be drawn in by capillary forces where it may not be possible to push it. This property also helps to keep the impregnant in the porosity when applied impregnating forces are removed."
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