Congealing applications, waxes

The measurement of the needle penetration of petroleum wax (ASTM D1321, IP 376) gives an indication of the hardness or consistency of wax. This method uses a penetrometer applying a load of 100 g for 5 s to a standard needle with a truncated cone tip. The sample is heated to 17°C (30°F) above its congealing point, poured into a small brass cylinder, cooled, and placed in a water bath at the test temperature for 1 h. The sample is then positioned under the penetrometer needle, which when released penetrates into the sample. The depth of penetration in tenths of millimeters is reported as the test value. This method is not applicable to oUy materials or petrolatum, which have penetrations greater than 250. 

Lastly, some glues harden, at least in part, by congealing or freezing as they cool. Such glues are often called hot melts . Older examples of hot melts include the hot applied resins and waxes and, to some extent, the hot animal glues. Synthetic polymer hot-melt glues have recently become widely used in industry and may have conservation applications as well. 

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