Quote:
Originally Posted by bncapass1
Sorry for resurrecting an older post but this topic fascinates me. The Rolex Tritium era ran from 1964 – 1997. The mixture process was Tritium, which is in its natural gas state, is then infused with a solid, then ground to a fine powder and then mixed with phosphorescence zinc sulfide. Zinc sulfide on its own will glow very briefly after being hit with a UV light but then fades rapidly after the light source is removed. In Tritium luminous compound, the radioactive decay bombards the phosphorescence zinc sulfide produces a continues glow. The caveat is from the moment the compound is mixed and applied, Tritium starts to lose it radioactivite decay reaching a half life after 12.5 years. Now, one would think a 1994 Submariner being more than 25 years old would not glow at all however I find even today that many even early 90's sports models can still be seen in the dark after your eyes adjust. It’s very faint but you can still see the remaining radioactive decay at work charging the zinc sulfide. What is perplexing to me is Singer, who made dials for Rolex, seems to have used two different types of radioactive luminous compounds. One that would glow after hit with a UV light but rapidly fade after the light source is removed like my two 1970’s Datejust’s and my 1980 Air King with the other like my three 1990’s sports models which do not react to any light source at all including a UV light yet you can see the very faint glow in pitch dark after you eyes adjust.
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You are right there are anomalies which point to variances in production.
As well as the (Circa +/- 1 year) the very well-known 1967 ZS dials that are very bright.....nearly all 70's 37.5 mm Daytonas lume up strongly, as do many Datejusts and a lot of DayDates!
And I have had a few 90 Subs that had the fag-end of luminosity too, as you have noted.
So clearly different manufacturing materials and processes were used.