@Ulrich_Baer
Here are some examples of HDGlass. On first picture you can see one layer. Its very transparent without getting brown. The second picture shows a part for a baby bottle. Printed slowly with 210 - 225°c on up!mini.
As i can see HDGlass is more or less PETG, I wonder if the teat would become more transparent if printed faster - or are there multiple shells/airgaps/filling.
Maybe its quite the same, but the result seems different…