  Deep images in the 10 micron spectral region have been obtained for five
massive Galactic globular clusters, NGC 104 (=47 Tuc), NGC 362, NGC 5139 (omega
Cen), NGC 6388, NGC 7078 (=M15) and NGC 6715 (=M54) in the Sagittarius Dwarf
Spheroidal using ISOCAM in 1997. A significant sample of bright giants have an
ISOCAM counterpart but only < 20% of these have a strong mid-IR excess
indicative of dusty circumstellar envelopes. From a combined physical and
statistical analysis we derive mass loss rates and frequency. We find that i)
significant mass loss occurs only at the very end of the Red Giant Branch
evolutionary stage and is episodic, ii) the modulation timescales must be
greater than a few decades and less than a million years, and iii) mass loss
occurrence does not show a crucial dependence on the cluster metallicity.
