I didn't know those fine details about the manufacturing process, but that all makes a lot of sense given the frequency of disc rot with those Polygram discs. Like many folks I have a soft spot for them, mostly because so many "target" CDs are West German Polygram discs - not to mention because the West German Polygram plant was the largest in the world in the early days of CD and so a lot of the LP titles we early adopters were eagerly awaiting to come out on CD when supplies were constrained up until about late 1985 ended up coming from that Polygram plant when they finally showed up in the US bins.
Nowadays, though, when thrift stores, Discogs, and eBay provide a lot of options for various physical pressings of many 1980s CD titles, I have been struck at just how cheap and flimsy those old Polygram discs are. Later Polygram discs, while still all aluminum, dispensed with the tapered edges and are of consistent thickness and more normal weight - and not coincidentally, they don't vibrate in players. Still, though, whenever I am looking to acquire an album on CD and the CD exists in both solid-aluminum and plastic-hub pressing versions (with the identical musical data on both), I will buy the plastic hub version every time.
I took a micrometer screw gauge:
1-„YEDS-18“, made by Sony for service technicians for adjustments on CD-players, produced with tight tolerances, birefringence below 50nm, variation in DC-level and HF-envelope below 3%, the mothership of all compact discs made in Sony‘s plant, around 1983:
Thickness: 1.23 mm
2-„The Köln Concert“, my second compact disc, made by Polygram, bought in 1984, still impacts my life in 2021 as a plotpoint in a documentary feature screened on Berlin International Film Festival -
thickness:1.24mm
But one can see that the clear enamel
on the label side builds up on the outer
rim. This adds 1/10th
One of the first UV - hardening enamels in industrial use btw.
3- Köln Concert reissue from 1990 by Polygram. The issue from 1984 misses
three notes, this is why I bought the reissue.
No typical Polygram look anymore, no galvanised center hub, shiny edges,
enamel very even, no buildup:
1.14 (!) I measured twice.
4- My very first one, Lou Reed, „Transformer“ issued 1983, Polygram-
1.26mm
5-Keith Jarrett „Solo Concerts Bremen/Lausanne“, typical early Polygram look:
1.18mm
6- Sting , „Nothing like the Sun“,
this time I measured more
to the center, Polygram, 1987-
1.29mm
7–„Halla Morgana“, I even worked for some weeks in this long defunct CD-plant, CDP in West Berlin, looks very thick and heavy, polished edges-
dissappointing 1.19mm.
It was not in production when I was there, so…
8- McCoy Tyner, „Echoes of a Friend“
manufactured by JVC, 1986-
1.24mm
9- Geinoh Yamashirogumi „Yamato Genjoh“, JVC 1994-
1.24mm
10-the latest, Markus Stockhausen
„Wild Life“, he dared a three CD-box in 2020, I wonder where he found a plant,
but close to the TOC, in letters not higher
than 0.3mm, it reads „Sony Music“- but in
times of globalization, the plant could be in Lithuania-
1.18mm
So, the Polygrams vary, but not all are thinner.
The thinnest is 1.14mm, the thickest 1.29mm.
No CD rot btw, not one. I once had a portable where the magnetic clamper was
weak- it grinded the aluminium off the inner
hub when the CD sped up. But these „holes“ never expanded over the decades.