Recently, Glass and Krisch have extended the Vaidya radiating metric to include both a radiation fluid and a string fluid (1999 Class. Quantum Grav. 16 1175). Mass diffusion in the extended Schwarzschild atmosphere was studied. The continuous solutions of classical diffusive transport are believed to describe the envelope of the underlying fractal behaviour. In this work we examine the classical picture at scales on which fractal behaviour might be evident.