Cosmoline

Any collector who has acquired a Curio & Relic military firearm knows the smell of Cosmoline or one of its foreign counterparts. We both prize and curse this stubborn preservative. Its ability to protect a firearm through decades of storage earns our appreciation. Its ability to strenuously resist almost any removal method earns our ire.

Cosmoline is the trademark name for a class of petroleum based preservative and rust preventative products first trademarked in 1892 by E.F. Houghton & Company. Interestingly, it was originally marketed as a pharmaceutical product. Cosmoline was used as an ointment to disinfect wounds on people. It was used by veterinarians to treat cuts, bruises, and other minor injuries on animals. It was even used to relieve swelling in cow's udders.

It's still offered as a health product in different parts of the world, such as India.

In addition to classically branded Cosmoline, there are other products available (such as Brownells Rust Veto) that are nearly indistinguishable from the original.

There are many ways to attempt removal of Cosmoline. Some work fairly well; some are actually dangerous; and some are a waste of time. Since Cosmoline melts at around 120 degrees Fahrenheit, most of the better methods involve application of heat. However, Cosmoline has a flash point of 365 degrees Fahrenheit, so be careful not to apply to much heat or expose it to open flame.

M1 Garand trigger assembly coated with Cosmoline

If the Cosmoline is fairly fresh or was stored in a hermetically sealed container, it may retain its initial grease-like consistency and should wipe off (mostly) with a rag, leaving only a thin film that responds well to traditional cleaning techniques. However, if it has been exposed to air for any length of time, the volatiles will evaporate leaving behind a thick, wax like, solid material. The longer the exposure to air, the tougher this residue is to remove. This is when the cursing usually begins.

Some of the methods that I have heard of or have tried myself are: using a heat gun to melt the Cosmoline, allowing it to drip off or wiping it off as it loosens; boiling the parts (if they are small enough) in a pot of water; wrapping the item in paper towels or rags, then wrapping black plastic over that and placing the bundle in the sun for a few hours. Using solvents is another popular technique. I’ve heard people recommend everything from gasoline to rubbing alcohol, followed by scrubbing. There’s also packing the parts in an absorbent material such as Whiting or talcum powder and applying heat; and last but not least, running the disassembled gun through a dishwasher.

Varustaleka Soviet Cosmoline

I cannot recommend using gasoline, paint thinner, or industrial solvents for this process. They are either too dangerous, too expensive, or likely to damage the finish or wood of the firearm.

I have tried soaking Cosmolined parts in kerosene. While it softened the Cosmoline to some degree, other things worked better. Surprisingly, I had better luck with Simple Green and scrubbing with rags. Note, I’ve read that Simple Green can react with aluminum. Purple Degreaser is another solvent I’ve heard works very well, though it can also be hard on aluminum.

Regardless of which method used, the firearm will need to be cleaned further as Cosmoline has a tendency to hide in the smallest nooks and crannies. 

I did try the dishwasher method on rifle stocks. This was done under agreement with my wife that I would replace the dishwasher if it broke during the process. When we sold the house several years later, the dishwasher still worked just fine. As a bonus, the stocks came out looking nearly new.

A few warnings on the dishwasher method: do not use it on a stock with important cartouches or stampings as the hot water will likely raise the grain enough to obliterate them; second, be prepared to immediately oil any metal parts that cannot be removed as they will be completely free of oil and will flash rust as they cool; most importantly, do not use this method on a stock that has been repaired as the heat and moisture will almost certainly break down any adhesives.

After going through this process the stock may need to be sanded and will certainly need to be refinished. For military firearms a few coats of Boiled Linseed Oil will usually suffice.

There are many additional references for Cosmoline removal online. Each individual needs to find the method that works best for them. Anyone attempting Cosmoline remove should take their time and be cautious. It’s the best way to have a harmonious outcome.