They say you can’t judge a book by looking at the cover. In a similar way, you can’t judge a grease by looking at the color.
Industrial lubricant customers often ask for specific greases by color – which is somewhat surprising, because the color has nothing to do with the application or the lubricating properties of the grease. As we point out in a recent white paper on the appearance of greases, a grease is composed primarily of its base oil, followed by the thickener and some additives. The color is simply a dye that the manufacturer adds, mainly to make it easier for the user to identify the grease. If you have been using, say, a red or green grease from a certain manufacturer for a specific application, check the name for good measure. However, if you switch to another manufacturer, be sure to check the label or product data sheet to be sure it is suited to your application – two different manufacturers may produce greases with the same properties in different colors.
In fact, grease colors from the same manufacturer can vary as well, depending on where the grease is made. That is because the base oil used at one refinery may differ slightly in color from that of another. The same grease product from two different manufacturing locations can show differences in color intensity or tone. You may see this difference in greases that contain dye, but you will definitely see it in greases that are sold with no dye added.
Bottom line, do not rely on color to determine whether you have the right grease for your application. Check the specification on the label, the manufacturer’s data sheet or website.
Grease can also change in appearance during storage, developing a lumpy or grainy texture or minor surface cracking. This is typically associated with oil separation, which is a normal occurrence after a period of weeks or months, and does not indicate diminished lubricating performance. You can restore the texture of the grease simply by stirring it, or by using a grease pump to dispense it.
If you find a small amount of separated oil in new, unopened grease containers, you can simply pour the oil off or remove it with an absorbent material. Or you can stir the oil back into the surface of the grease and smooth it out with a spatula.
Oil may also separate from the thickener when the grease is applied to moving parts, which again is normal. The thickener holds the oil in place when the grease is administered, then releases the oil and additives to lubricate the moving parts. When the parts stop moving, the oil is then reabsorbed back into the thickener – or it should be. If a significant amount of oil is “bleeding” or not reabsorbed, it could be an indication that you’re using the wrong grease or it is incompatible with a prior grease.
When transitioning to a new grease, it’s important to make sure that it meets the requirements of the application. Different greases use different thickening agents, and they are not necessarily compatible. Conversion to a grease with different thickener should especially proceed with caution.
Our two-page white paper goes into more detail about the makeup of greases and why they may change in appearance. It also contains some valuable tips for the proper storage and handling to make sure you get the optimal life and performance from your grease inventory. Download the paper, and as always, feel free to contact us if you have any questions or concerns about the application of grease in your operations.