FIGS 4 FUN
MORE INFO ABOUT FIG ROOTING MEDIA
Two very important factors must be balanced when choosing a rooting medium: moisture and air. You need to have a mix which allows for moisture to be retained, but one which does not allow the water to completely saturate the medium so that there is no air (oxygen) in the medium. Texture or coarseness is an important factor in balancing these two requirements. The smaller particle sizes tend to allow the medium to become saturated, excluding all air and holding too much moisture. Larger particles will hold less moisture and allow air. Most sand is too fine to prevent saturation.
The use of a clear cup when rooting allows you to see the moisture in the rooting medium, and to assess whether there is sufficient air in the medium, as well.