[M.D. Holloway]

Water proof huh? Try this, apply a generous amount of grease to the palm of your hand. Run tap water over the grease while mixing it with the fingers from the other hand. Within seconds you may notice a radical change. The grease may turn a light milky color. The grease is being emulsified. The grease may even completely break down. You may be able to see the palm of your hand that previously contained grease. If this is what the grease will do in your hand under minimal stress and water, imagine what will occur in a bearing or journal that comes in contact with water, steam or condensation under stress!

Excellent grease will not wash out and will actually be very difficult to remove from your palm even after a generous amount of water has been applied.

There are three components of a grease - the base oil, the thickener, and performance additives. Traditionally, the base oil was considered the major component. In many conventional greases it can be found to be 70% to 95% of the grease. Because of this reason, many bearing manufacturers consider the base oil viscosity to be a predominant factor in grease selection and approval for their products. The fact remains that, with recent technological developments in the two other components (thickeners and performance additives), the base oil has become less of a determining factor and more of a component of a synergistic effect among the three.

The second component is the thickener. This is what gives the grease its body. The thickener is typically how grease is characterized, which can lead to confusion and in some instances misrepresentation. Producing a thickener can be a very complicated process. One manufacturer may attempt to produce one type of thickener for grease only to have it fall short in performance compared to other products of the same thickener type. The raw materials used and the manufacturing process may dictate if a thickener will provide superior or marginal performance. The thickeners chosen may be simple metal soaps, complex soaps, synthetic organic thickeners, or inorganic gelling agents. In many instances the thickener is referred to as the soap of the grease even if it is not chemically defined as a soap. This is becuase the first multipurpose grease formulas were calcium, sodium or lithium soaps. Thickeners can account for 2% to 40% of the grease.

The performance additives incorporated into the grease formulation provide specific functionality such as rust and corrosion resistance, oxidation resistance and even improved lubricity when additives such as molybdenum disulfide or graphite are used. These chemicals, both solid and liquid, can account for 1% to 25% or more of the final grease formulation, depending on what performance criteria and targets need to be met. In the table I provided earlier, the various type or classes of base oil, thickeners and performance additives are listed. This list is very general and should not be considered complete but rather offered as an indication of the various materials that are used in combination to achieve performance.