Cleaning Precision Optics

Cleaning precision optics by Chuong Tran

Cleaning optics with 99.9% isopropyl alcohol (IPA) is a common practice due to several key advantages:

• Effective Contaminant Removal:

  • IPA excels at dissolving and removing various organic contaminants, such as oils, fingerprints, and residues from adhesives or cleaning solutions. These contaminants can significantly degrade the performance of optical surfaces.  

• Rapid Evaporation:

  • 99.9% IPA evaporates quickly, minimizing the risk of leaving behind residual moisture or streaks on the optical surface. This is crucial for maintaining the clarity and integrity of precision optics.  

• Relatively Safe for Many Coatings:

  • When used correctly, IPA is generally considered safe for many common optical coatings. However, it's very important to check compatibility with specific coatings, because some very sensitive coatings may be damaged.

• Purity:

  • The high purity of 99.9% IPA minimizes the risk of introducing new contaminants during the cleaning process. This is especially important for precision optics where even microscopic particles can impact performance.

Cleaning Procedure:

1. Preliminary Dust Removal:

   • Use a clean, dry air blower (bulb blower) to remove loose dust and particles.

   • A very soft, clean optical brush can also be used. This is a very important step, because dragging dust across a lense with a liquid will cause scratches.

2. Preparation:

   • Gather the following materials:

     • 99.9% IPA

     • High-quality, lint-free optical wipes or lens tissue

     • Clean, powder-free gloves

3. Wiping Technique:

   • Dampen (do not saturate) an optical wipe or lens tissue with IPA.

   • Use a gentle, sweeping motion. Avoid applying excessive pressure.

   • Wipe in one direction, and avoid circular motions that can redeposit contaminants.

   • Use a fresh wipe for each pass.

   • "Drop and drag method" can be very effective. Place a drop of IPA on the edge of a lens tissue, and then gently drag the wet portion of the tissue across the optic.

4. Drying:

   • IPA evaporates quickly, but you can gently blot the optic with a clean, dry optical wipe to remove any residual moisture.

   • Allow the optic to air dry completely before use.

5. Inspection:

   • Inspect the optic for any remaining streaks or particles.

   • If necessary, repeat the cleaning process.

Key Considerations:

• Frequency:

  • Clean optics only when necessary. Over-cleaning can increase the risk of damage.

• Storage:

  • Store IPA in a tightly sealed container to prevent contamination.

• Disposal:

  • Dispose of used IPA and wipes according to local regulations.

Important Note:

• For extremely sensitive or valuable optics, consider consulting with a professional optical cleaning service.  By following these steps, you can minimize the risk of damage and effectively clean your precision optics with IPA. However, it's important to acknowledge that:

• Not a universal solution:

  • While IPA is effective against many contaminants, it may not remove all types of residues, such as inorganic salts or certain specialized coatings.

  • As pointed out by some sources, IPA may not be ideal for some Fiber optic cleaning applications.

• Precautions are necessary:

  • IPA is flammable, so safety precautions are essential.  

  • Improper use or excessive application can still damage sensitive coatings.

Therefore, 99.9% IPA is often a valuable tool for cleaning precision optics, but it should be used judiciously, and with an understanding of its limitations.