Immersion Oil & The Microscope – A Paper by John J. Cargille
Most scientists who are using microscopes are not microscopists—they have another field of specialization. In many cases, their understanding of microscopy is limited to on the job training that allows them to get by proficiently. This classic paper by John J. Cargille attempts to broaden scientists’ understanding of the “business area” of the microscope, between the condenser and the objective, as it is affected by the use of oil immersion objectives. The paper also expands on properties of immersion oils and how they can be more fully utilized.
Cargille’s Expertise with Immersion Oils
Cargille Laboratories has consistently led in the development and standardization of immersion oil for over 42 years. Here is the record:
- Developed non-drying immersion oils (1940).
- First to standardize index and temperature values.
- Developed oils of different viscosities.
- Developed low fluorescence immersion oil (1940).
- First to print key optical properties on every bottle (1942).
- First to print full tables of optical and physical properties in Data Sheets (1946).
- First nondrying immersion oil adopted by major microscope manufacturers (AO, B&L)
- Cargille specifications adopted by U.S. Department of Defense.
- Developed the first very high viscosity oils for horizontal, inverted and projecting microscopes in cooperation with US Department of H.E.W. (1950).
- Developed the first PCB-free immersion oils (1971).
- Supplies oil to meet British immersion oil specifications.
- Collaborated with DIN and ISO committees in developing international standards and served as liaison with American microscope manufacturers.
- Provides modified formulas for special applications supported by Extended Properties Technical Bulletins.
- First to provide Material Safety Data Sheets to insure compliance with OSHA.
- First to establish a Refractive Index Laboratory with primary standard, computerized formulation and modeling capabilities for R&D, QC and Customer Service.
- First to modify immersion oil formulations for use with various instruments such as calibration, mounting, contact and interface fluids in the fields of fiber optics, lasers, optometry, and optical engineering where special index, temperature, wavelength, viscosity, density and adsorption characteristics are required.
- First in worldwide distribution of immersion oils.
- Foremost in supplying US and foreign microscope manufacturers with “accessory” oils for new instruments.
Immersion Oil Selection Guide
For Normal Light Microscopy: Types A and B are virtually interchangeable and are miscible with each other for intermediate viscosities. Produced in larger quantities than other types, Types A and B are the most economical. The deciding factor in choosing between them is the optimum viscosity for your particular application.
Type A, at 150 centistokes, reduces any tendancy to trap air, especially helpful to beginning students. Air bubbles cause image degradation.
Type B, at 1250 cSt, is thick enough for viewing multiple slides with one application. This saves time during batch processing.
Automated Hematology Systems: Use Type 300; Automated Hematology Systems depend on accurate, precisely controlled physical and optical properties of immersion oil for successful imaging and mechanical processing. Type 300 is designed and manufactured to meet the stringent requirements of this equipment, which include specialized viscosity and exacting controls for its consistency.
Inverted, Inclined, Projection, and Long Focus Instruments: Use type NVH or OVH; The greater the gap between the cover glass and objective, or between the slide and condenser, the more desirable high viscosity becomes. The very high viscosities of Type NVH at 21,000 cSt and Type OVH at 46,000 cSt give excellent results for these applications.
Blending Oils from the Miscible Group: The Miscible Group of immersion oils is A, B, 300, NVH and OVH. Users can easily blend any two immersion oils from the Miscible Group to obtain an immersion oil with an intermediate viscosity while maintaining the optical properties common to both.
Fluorescence Microscopy: Extremely low fluorescence is achieved by Type LDF and Type HF. Type FF is virtually fluorescence-free, though not ISO compliant. Type HF is slightly more fluorescent than Type LDF, but is halogen-free. For most non-critical fluorescence microscopy applications, Types A and B are sufficiently low fluorescing. Viscosities for Type LDF, HF, and FF are 500 cSt, 700 cSt and 170 cSt, respectively. Types A and B are 150 cSt and 1250 cSt.
Elevated Temperatures (>23°C to 37°C): Use Type 37. Elevated temperatures can be due to substage illuminators, “hot stage”, or other causes – ideal situations for Cargille Immersion Oil Type 37. Developed specifically for working at human body temperatures, Type 37 has a refractive index of 1.515 and a viscosity of 1250 cSt at 37°C. solving the problem of image degradation above the standard calibration temperature of 23°C. Users can blend for their own working temperature; blending Type B, with a viscosity of 1250 cSt at 23°C with Type 37, 1250 cSt at 37°C maintains a constant 1250 cSt viscosity and optical values and places the temperature of calibration proportionally between 23°C to 37°C.