[Insomniac]

Anyone got any objective or practical experience to shed light on the relative durability of normal aluminium plus quartz overcoat versus enhanced coatings (aluminium, plus quartz plus overcoat of titanium dioxide or pentoxide).

Since no one has probably used 2 identical mirrors with the 2 coatings under identical circumstances to test this out, I suppose it'll boil down to anecdotal experience, unless there are some good scientific reasons why one should be superior. Isaac from C Qin Pty LTd says the enhanced coatings are subject to greater stress & don't last as long. But I guess those offering the enhanced would not jump to agree.

Some say the few percentage points gain in reflectivity of enhanced coatings can't be easily appreciated by the eye anyway, and are not therefore worth the extra expence. Since I'm shipping a large mirror from N.Z, my main concern is that I have to re coat as infrequently as possible!