According to Kramer publication (Curr Protoc Mol Biol. PMC 2012 July 1)

It is mentioned under "SL RT primer"

Transfer to new tube, then overlay with 100 μL molecular-biology grade mineral oil. Heat to 95°C for 10m. Reduce heat slowly to 75°C. Hold temp at 75, 68, 65 and 62°C for an hour each, hold at 60°C for several more hours. Transfer primer from under oil to new tube. This step should never need repeating if the primer is never heated above room temperature.

From the above protocol it is not clear about "Reduce heat slowly to 75°C".

It would be nice for me if anybody clarify this.

thanks