Which factor does NOT contribute to the thickening of melted chocolate?

The factor that does not contribute to the thickening of melted chocolate is its temperature being very cold. In fact, cold temperatures typically lead to the solidification of chocolate rather than thickening. When chocolate is chilled, its cocoa butter begins to solidify, causing the mixture to become thicker and potentially difficult to work with as it hardens.

On the other hand, overheating chocolate can lead to a change in its viscosity. When chocolate is overheated, it can become thick due to the degradation of fats and the alteration of its crystalline structure. Incorporating air can also cause thickening as it creates a lighter texture. Lastly, adding moisture to chocolate, such as from water or other ingredients with a high moisture content, can cause it to seize and thicken as the cocoa solids and sugar clump together. Thus, among the factors presented, very cold temperatures do not contribute to the thickening of melted chocolate.