Tumbling Media to Remove Grease
Not all tumbling media is created equal. Each type of media is designed for a specific use and task, such as for removing metal burrs from machine parts, or polishing metal to a high shine. Tumbling media designed to remove rust will not be able to add a protective coating over your parts. It is important to select the right media for the job every time. If you need to remove grease and oil from your parts, there are a few different media choices that can do the job effectively. Before trying any cleaning method, check with the manufacturer of the part to ensure that it is safe to use in a tumbling machine with tumbling media to avoid damaging the part.
Corn cob: Corn cob is effective at removing grease and oil from machine parts because it is naturally absorbent. The soft material will not scratch or damage the metal, but the absorbency of the corn cob makes it one of the best choices for removing grease and oil. If you want a little extra help in removing the oil, try adding a tablespoon or so of mineral spirits to help strip the metal.
Walnut: For thick oil or grease that is too tough for just corn cob to remove, you can add a little walnut shells to the corn cob mixture before tumbling. The walnut shells add a little extra abrasive power to the mixture that can really help scrape the unwanted grease off of the metal. Take care when using walnut shells on softer metal, as the shells could scratch the metal or damage delicate metal parts. Always start with just corn cob at first, then move to walnut shells later if you find you need a tougher cleaning method. Add in a tablespoon or two of mineral spirits to the corn cob and walnut shell media for the ultimate cleaning and stripping concoction.