What kind of grease should be used for greasing the collection substrates?
The most commonly used grease in impactor measurements is Apiezon-L, because of its purity and low evaporation properties. Dekati Ltd provides Apiezon- L for substrate greasing but other types of greases may also be used as long as the grease has low evaporation characteristics even in low pressures (min 100 mbar), a thin and smooth layer of used grease can be applied on the substrates, and the grease has low enough viscosity so that the air flow inside the impactor does not blow the grease out of the impactor collection substrates. Before applying the grease on the substrates, it should be dissolved in a suitable solvent e.g. carbon tetrachloride, toluene or acetone. Dissolve the grease in the solvent by adding the grease in the solvent little by little until you reach grease/solvent ratio of about 1/20-1/30. The Apiezon-L grease is also available from Dekati as a spray.
