Zeiss says cleaning lenses with anything other than their lens cleaner voids the warranty. I wouldn't buy a Zeiss magnifying glass on sale.
You may just want to ask Zeiss directly if they have ever asked anyone what they used to clean the lenses and then voided the warranty as a result of the answer LOL. I've sent in Zeiss scopes for warranty work and for reticle changes and have NEVER been asked that.
By the way, I just looked at one of my Zeiss manuals, and NOWHERE does it state what you claim. I'm not saying it may not be in another product's manual, but I don't recall reading that in any of mine and have used Zeiss for decades.
FROM ZEISS MANUAL:
Care and maintenance
Your riflescope has ZEISS LotuTec ® coating. The effective protective coating for the lens surfaces noticeably reduces contamination of the lenses through an especially smooth surface and the resulting water-beading effect. All types of contamination stick less and can be quickly and easily removed without smearing. LotuTec® coating is durable and abrasion-resistant.
Your ZEISS riflescope requires no special maintenance. Do not wipe coarse particles (e. g. sand) from the lenses. Blow them off, or use a soft brush! Over time, fingerprints can corrode the lens surface. Breathing on the lens and polishing with a clean optical cleansing cloth/tissue is the easiest method of cleaning the lens surface.
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I also just looked at a pre-Lotutec manual. Again, there is no mention of what you claim.
