In order to achieve optimal performance, it is important to allow a refrigerated flux to warm to room temperature for an adequate amount of time before use. Recently Brandon Judd performed a test on a water-soluble flux in a 6oz (150g) cartridge, where he refrigerated the flux to 0oC and recorded the internal temperature of the flux as it reached room temperature. As can be seen in the graph, the flux took approximately 2.5 hours to reach room temperature.
Brandon mentioned: “When compared to solder paste, flux alone takes longer to warm up, as it does not have the metal powder in it to help accelerate the heat transfer. You are much better off making sure the flux is removed from the refrigerator in advance in order to prevent sacrificing the performance of the flux by not waiting for it to warm up.” Brandon will be overlaying the results of thawing paste to prove out the theory. None-the-less, the important message here is to properly thaw out flux before usage.