![Image](https://photos.smugmug.com/Other/n-xC6Rt/Microscopy/i-MztJs2f/1/23e8247e/M/IMG_2248-M.jpg)
I've had a chance to examine the front lens of this Zeiss C-apo 63x/1.2 water immersion objective that was being used on an inverted microscope for life sciences microscopy and possibly cell cultures.
The front lens has a haze that could not be cleaned with 100% ethanol or water:
![Image](https://photos.smugmug.com/Other/n-xC6Rt/Microscopy/i-BJDgLNR/0/49807769/L/IMG_2348-L.jpg)
front lens as seen with coaxial reflected light;
![Image](https://photos.smugmug.com/Other/n-xC6Rt/Microscopy/i-kD8h9zM/0/4d23e956/L/IMG_2349-L.jpg)
front lens as seen with oblique reflected light.
There is no visible birefringence or bireflectance in either transmitted or reflected polarized light.
The random, evenly distributed pattern on the glass seems to suggest that some kind of aqueous or other solution was left to dry on the lens (not cleaned off after use) and when the solvent evaporated it left a residue.
I can't really tell if the substance has actually eaten into the glass.
Does anyone know what substance could have caused this, and whether the damage is salvageable? What other cleaning agents are safe to try on this particular objective? Note that there appears to be some damage to the lens mount so cleaning agents could seep inside:
![Image](https://photos.smugmug.com/Other/n-xC6Rt/Microscopy/i-3gmqsp6/0/9aa8bd7f/L/reflected%20coaxial%20illumination%204x-L.jpg)
(front lens as seen with coaxial reflected light, photographed through 10x eyepiece and 4x objective)
Thank you very much for any ideas.