Lens Lens Fungus and Haze Removal Wiping: Hydrogen Peroxide Ammonia Formula and Coating Safety

1. Pathological mechanisms of lens fungus and haze

In an environment with relative humidity above 60% for a long time and poor ventilation, mold contamination can easily break out inside old lenses:

1. Biocorrosion of fungal hyphae (Mycelium):

• Common Aspergillus aerogenes and Cladosporium colonies on the surface of the lens use the volatile lubricating oil or dust inside the lens barrel as nutrients to spread out a spider-like hyphae network of tree roots.
• Fungi secrete strongly corrosive organic acidic excretions such as hydrofluoric acid during their metabolism. These acids will erode the anti-reflective metal oxide coating (Anti-Reflective Coating) on ​​the glass surface, and even directly bite irreversible microscopic pitting holes (Etching) on ​​the expensive optical glass.

2. Oil and vapor condensation in Haze/Fog:

• The aperture damping grease of old lenses ages and deteriorates, and low-boiling point volatile oil molecules condense evenly on the surface of the lens in the lens, forming a layer of white mist like frosted glass, causing strong backlighting to whiten and collapse contrast.

2. Lens safety disassembly tools and thread annealing marking specifications

Never use a vise to disassemble a lens blindly and violently. You must prepare watch-level precision tools:

1. Specialized Lens Spanner Wrench:

• Use a tic-tac-toe lens removal wrench with a flat-tip and round-tip double-headed carbide blade, and adjust the span so that it can be accurately inserted into the two tiny grooves of the lens retaining ring (Retaining Ring).

2. Rubber Lens Suction Cup:

• For the front nameplate ring without threaded grooves, use a high-adhesion conical oil-free rubber sleeve, press down and use friction to smoothly unscrew the nameplate counterclockwise.

3. Key marks and direction memory:

• The lens in the lens tube is usually a complex positive and negative double concave and convex lens, and the slight curvature of the front and back sides is easily confused!
• Before taking out the lens, use a pencil or fine paint pen to lightly draw a "$\to$" pointing arrow on the frosted edge (Rim) of the lens** to definitely mark the front direction facing the subject.
• Lenses must be placed in a single layer in a special white silicone partition tray. Do not stack them on top of each other to scratch the mirror surface.

3. Chemical mildew removal formula: "Hydrogen Peroxide & Ammonia" classic bath

The alcohol on the market can only dissolve oil stains and has insufficient killing power against stubborn fungal spores and mycelium residues; the classic hydrogen peroxide-ammonia solution must be used:

1. Dispensing ratio (1:1, ready for use):

• Take 3% medical hydrogen peroxide ($H_2O_2$): 50ml;
• Take household light unscented ammonia (Ammonia concentration is about 5%~10%): 50ml;
• Mix both in a 1:1 ratio in a glass beaker.

2. Chemical coordinated attack and defense reactions:

• Strongly oxidizing hydrogen peroxide releases new ecological oxygen, which can instantly disintegrate fungal cell walls and completely kill spores;
• Weakly alkaline ammonia acts as a highly efficient surfactant, quickly dissolving the lipid dirt and organic acids wrapped in the fungus shell, and completely peeling off the dead hyphae from the glass surface.

3. Soaking and gentle wiping method:

• Completely immerse the removed moldy single lens in mildew removal solution for 5 to 10 minutes;
• Take it out and place it on dust-free lens wipe paper (such as PEC-PAD), put on powder-free latex finger cots, and add 2 drops of lens cleaning fluid;
• Adopt the center-outward spiral wiping method (Spiral Wipe): draw concentric circles from the center of the lens and move gently towards the outer periphery. Wipe a piece of dust-free paper once and throw it away immediately. It is strictly forbidden to wipe back and forth with the same piece of paper to prevent the falling hard quartz dust particles from pulling out permanent scratches on the coating.

4. Determination of coating damage and ultimate storage to prevent recurrence

1. Coating etching evaluation after mold removal:

• Place it under a high-brightness LED point light source and observe through light: If a faint translucent matte tree root mark is left at the original hyphae after mold removal, it means that the coating has been bitten by bacterial acid.
• As long as the main light-transmitting surface is not peeled off, the impact on the actual imaging contrast is usually less than 3%, and there is no need for polishing (polishing will destroy the curvature of the aspherical surface).

2. Ultraviolet irradiation to prevent recurrence (UV Curing):

• Clean and dry the lens and expose it to a 254nm short-wave UV germicidal lamp for 15 minutes to completely inactivate microscopic active fungal spores lurking in the corners of the lens barrel.

3. Reassembly and Sealing:

• Apply high-temperature resistant, extremely low-volatility perfluoropolyether (PFPE) special non-volatile optical grease;
• Tighten the pressing ring to a moderate degree to avoid stress birefringence deformation that may damage the image quality.

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