Probably the crucial point in the 13 page thread about the current EL's covering that Patudo has linked to, is the information that the OP received from Swarovski:
. . . In accordance with its corporate philosophy, Swarovski Optik is committed to using top-quality, sustainable materials in its products. The armoring on the instruments in question is made of plastic (TPU). This material contains no plasticizers or protective agents, is low in allergens, and is biodegradable. As with all our products, we recommend regularly cleaning the surface of the instrument with a mild detergent and a damp cloth.
The particular properties of this material mean that optical changes such as clear abrasion, tears, and cracks may occur in the armoring when the product is subjected to frequent use
And when looking at the Swarovski site this morning, I came across the following:
Q. Is the NL Pure's armoring the same as the EL's?
A. The armoring of the
NL Pure - just like the armoring of the EL series - is made of TPU. TPU does not contain any softeners or protective agents, is low in allergens and a sustainable material. As with all our products, we recommend to clean the surface of the device regularly. The NL Pure binoculars come with a dedicated
soap & brush kit to clean the housing.
See at:
My Service
. . . So presumedly TPU is also used for the RA covering on the more recent SLC’s along with the rest of the current Swarovski production.
And as to the next question:
'Thermoplastic Polyurethane or TPU is referred to as the bridge between rubbers and plastics. The material appears rubber-like, which means it can be extremely flexible, durable and smooth to the touch. All these properties and compound versatility makes TPU widely used in many industries for coatings, components and customer goods. It is often used for
3D printing'.
From:
Treatstock
It may be due to it’s nature that TPU is a less durable covering than those previously used. This seems to be implicitly acknowledged in the first quote above: both the reference to biodegradability, and the qualifier in the last sentence. So perhaps someone with expert knowledge in the area may be able to provide further information.
- - - -
Unsurprisingly, Swarovski has had some problems with the long-term durability of various coverings. There was a batch of black vulcanite used on Habicht Porro prism binoculars back in the early 1950’s that’s gradually turned brown over the decades, see an image in post #3 at: https://www.birdforum.net/threads/second-hand-habicht-porro’s-to-use.391231/
And the natural rubber (?) covering used on the early RA Habicht Porro prisms dating from the mid 1970’s, has invariably severely perished, see a typical example fitted with newer eyecups. However, the problem abruptly ceased with later production, presumedly with the introduction of an updated composition to the covering.
Of course, Swarovski is not alone in this regard e.g. one common example mentioned both here and on Cloudy Nights is where the RA on older Canon IS units has become sticky.
However, what’s notably different with the current TPU covered Swarovski’s is how soon in the life of particular units that significant problems are occurring.
John
