Ceder wood oil for microscopic

Cedar wood oil is a traditional immersion oil used in light microscopy to improve resolution with high‑power (usually 100x) objectives by matching the refractive index of glass and reducing light loss by refraction.​

Why cedar wood oil is used

Cedar wood immersion oil has a refractive index around 1.51–1.52, very close to that of glass coverslips and objective fronts, so light rays pass through specimen–oil–glass with minimal bending, giving a brighter, higher‑resolution image.​

For this reason it was historically the standard immersion medium and is still sold specifically as “cedar wood oil for microscopy” or “immersion oil (cedarwood).”​

Practical and safety points

Only the oil‑immersion (100x) objective should be used with cedar wood oil, and a single small drop is placed between cover glass and lens to bridge the air gap.​

Cedar wood oil can oxidise and harden, leaving a sticky residue that may damage lens cement or coatings if not cleaned off promptly, so many modern labs now prefer synthetic immersion oils with similar refractive index but better stability, though cedar oil products remain available and effective when used and cleaned correctly.​