How to Clean Semrock Optical Filters

by IDEX Health & Science

Materials Required:

  • Latex or Nitrile gloves
  • Cleanroom wipes
  • Cleanroom swabs in various sizes
  • Deionized water
  • HPLC grade methanol
  • Cloth to dab swab on to remove excess liquid
  • Tweezers
  • Nitrogen Compressed Air Supply
  • Fluid dispenser fluid dispenser


  1. Blow dust off optical filter with compressed air prior to using swab and solvent to clean.
  2. With gloves on, lay out filters on a cleanroom wipe.
  3. Even with gloves on, only handle filters by the edges with tweezers or fingers for best results.

General Cleaning

  1. Select cleanroom swab size.
  2. Depress the fluid dispenser to flow cleaning fluid into the top, and touch the swab to the methanol (do not place swab directly into the fluid container).
  3. Touch the swab to the cleanroom wipe to remove excess liquid.
  4. Depending upon part size, apply swab to filter using a circular motion for round parts or an S-shaped motion for rectangular parts across the filter surface. It’s important to keep contact with the filter throughout this process.
  5. Turn filter over and repeat.
  6. Do not use the same swab side on the second filter side.

Stubborn Debris

  1. Select a new swab or use swab’s opposite side to clean second side of the filter.
  2. Touch the swab to deionized water.
  3. Touch the swab to the cleanroom wipe to remove excess water.
  4. Repeat the S-shaped or circular motion across the filter surface.
  5. Do not let deionized water dry before you apply methanol.
  6. For particularly stubborn debris, use a different sized swab.
  7. Touch the swab to deionized water.
  8. Remove excess liquid on the cleanroom wipe.
  9. Move the swab over the filter surface in a wiping motion.
  10. Turn swab over and repeat wiping motion.
  11. Touch swab to the methanol and repeat.

Do's and Don'ts

  1. Be gentle. Only wipe lightly or use the swab in an S-motion.
  2. Avoid scrubbing, especially close to the edges. Scrubbing will cause irreparable damage to the coating and/or edge paint.
  3. If the debris is not removed, use deionized water and methanol rather than trying to scrub parts.
  4. Remember to only handle filters by their edges, and to turn them over and repeat the process on the opposite side.