The evaluation of the exudation potential of AZS refractories is important in estimating the level of defects (e.g. cords, stones, etc.) that they are likely to produce in the glass bath, especially in the initial period of service life of the melting furnace. The glassy phase naturally contained in the AZS refractories tends to be partially and progressively exuded, i.e. expelled outside the blocks, towards the hot face.

This amorphous material, rich in Al2O3 and ZrO2, flowing down from the superstructure or being directly removed from the blocks of palisade and bottom by the melt, can give rise to major defects in the finished products.

Laboratory tests can be carried out following standard procedures such as ASTM C1223 (2 heating and cooling cycles), or other technical specifications such as those developed within ICG by the Technical Committee 11 (10 heating and cooling cycles).