As a Source Four ellipsoidal ages, especially in a damp climate or with outdoor use, it is possible to get oxidation between the shutters and divider plates making them difficult to move.
The shutter Divider Plates are made of 'electro-galv' material which provides a corrosion resistant coating with lubricity properties unaffected by the high operating temp.
ETC does not recommend applying any type of lubricant due to the extremely high temps, which causes the lubricant, or carrier substances to vaporize and redeposit over all the optical components damaging the dielectric coatings and/or substantially degrading performance.
As such, ETC recommends replacing the shutter Divider Plates and cleaning the Shutter Blades with steel wool.
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