The right refill fluid for Ritchie compasses
If you ever need to refill or top off the fluid in your Ritchie compass, the manufacturer recommends Isopar L, an odorless, colorless, refined synthetic fluid. Its low viscosity promotes quick swinging. Won't freeze or boil off at temperatures from -40º to 200º F., and it may be mixed with the mineral oil already in compasses made before 2001.
Always use Ritchie compass fluid. (Be sure to subject the fluid to a vacuum equivalent of 28 inches of mercury for a minimum of 15 minutes before sealing it in the compass. This step prevents the formation of a bubble in the fluid due to temperature changes.)
Ritchie began using Isopar L as dampening fluid during 2001. This fluid is a high-purity isoparaffinic solvent very similar to Odorless Mineral spirits. Ritchie changed to this fluid because it has a higher flash point and conforms to most of the world's shipping regulations. It is important to note that some other manufacturers use Isopar M as their dampening fluid.