External Medium on the Force of Adhesion

Factors on which adhesive forces depend include the temperature of the external medium, the presence of certain vapors 

In the deposition of dust in air, the temperature of the medium surrounding the dust-laden surface and also the temperature of the contiguous bodies themselves may vary over wide limits (for example, from—30 to +40 C).=  

In the impulse method the effect of air humidity is excluded, and hence the rise in the adhesive force with increasing temperature of the medium can only be explained by a change taking place in the properties of the contiguous bodies. 

The rise in adhesive force on painted surfaces (Fig. III.22) is clearly explained by the development of surface tackiness, which increases with temperature. 

It has been found experimentally that on placing a sample, previously coated with dust in air (at 20°C, relative humidity 50-60%), into a low-temperature medium (below 0°C) the adhesive forces increase sharply as a result of the freezing of the particles to the surface by virtue of moisture condensed between the bodies in contact. However, if the dust is actually deposited on the 

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