How to Remove Cosmoline
Dealing with The Protective Coating From Hell
Published: May 25, 2009
Updated: Nov 20, 2009 - minor wording changes; Aug 19, 2010 - major rewrite
I've always heard it called "Cosmoline". According to Wikipedia, it's a generic name for a whole class of rust-preventative coatings. Of course, Wikipedia is often politically-correct and dead wrong, so take that with a large grain of salt. There's a company that makes an actual line of products named Cosmoline, but they describe the rust preventative as a "colorless, thin film" which is definitely not what I'm talking about. Regardless of what it is, for the sake of tradition and convenience, let's just call it Cosmoline.
If you've ever gotten a new piece of equipment with a cast iron surface, you know what I'm talking about. Thick, brownish-yellow, sticky, just plain gross. It appears that it gets sprayed heavily onto the surface after finishing. It's sole purpose is to prevent that beautiful new top from turning into a rusty, pitted mess during its trip to you. The photo above shows a partially cleaned Grizzly table saw.
To say that Cosmoline is hard to remove is an understatement. In fact, its resistance to cleaning is almost legendary.
Over the years, I've tried lots of different things to remove Cosmoline. Most people try some form of acetone like paint thinner. They work OK, but they dry out really fast, which makes it hard to soften up the large chunks and globs that are down in grooves or slots. And, since they flash off so quickly, they let a thin layer of dissolved Cosmoline dry back onto the surface as you're wiping, making it really difficult to get the stuff completely off.
Also, paint thinners and removers like acetone have another bad side effect: they remove paint, which isn't surprising since that's their real purpose. Many if not most cast-iron tops have their edges painted and it doesn't take much to ruin the nice glossy finish or start completely taking the paint off.
And, let's not forget the noxious smell and the fact that's it's really bad for your lungs and poisonous. Oh, as a bonus, it's also extremely flammable!
There is, however, one product that I've found that's absolutely perfect for removing Cosmoline: WD-40! But wait, you say, WD-40 is a lubricant. Sorry, Grasshopper, but that's not true. Many people think it's a lubricant because they use it to loosen rusty bolts, but actually it's primarily a solvent. It penetrates and breaks down the rust, it doesn't oil it up. It apparently does contain a little oil of some kind, but not much.
Not only does WD-40 dissolve the Cosmoline, it does it better and faster than acetone. I really like the fact that it doesn't dry out, but sits there and works on softening up the Cosmoline. The spray and handy tube make it easy to get into grooves and slots, as well as bolt holes. Also, while acetone strips the metal completely bare, WD-40 leaves behind a slightly oily residue that repels moisture and protect the cast iron for a little while until you can get around to protecting it with something like Topsaver.
Let's take a look at how well WD-40 works. Here, you see a brand new jointer fence, absolutely coated with a stiff, sticky layer of Cosmoline. It was fairly well dried on, so this'll be a nice challenge. (Click on the photo for a larger view, use the arrow keys to move between photos)
Just spray on some WD-40. Doesn't need to be a ton, just cover the top well. This photo is just a few seconds after the WD-40 hits, the Cosmoline is already dissolving and beginning to run. Just take your fingers and lightly rub everything. It's quite gross yet oddly satisfying.
After less than a minute, a quick wipe with a paper towel removes almost all the Cosmoline, just leaving some of the large globs.
Another light spray of WD-40 and less than a minute later the fence is completely Cosmoline-free. Almost effortless.
Before and after. No heavy scrubbling, no noxious chemicals, very little time.
A regular toothbrush makes a perfect tool for getting into cracks and crevices. You can see clearly in this photo how the WD-40 is completley liquifying the Cosmoline. No need for wire brushes, the nylon bristles get everything clean as a whistle (which is an idiom I've never understood). The last time I used acetone, just a few seconds completely dissolved the paint from a scale like this.
Just a few minutes of light work and the jointer fence is completely clean and ready to install.
After you get your cast iron nice and clean, don't forget to protect it. As I said, WD-40 is a solvent. Despite it's somewhat oily feeling, it's not a lubricant and it's not a long-term protector. A day or two is OK, but you really need to use a product designed to seal the metal and ward off moisture. I've tried Topsaver, Dri-Cote, T-9 Boeshield, and several other specialized products as well as Johnson's Paste Wax. I currently use both TopSaver to seal and JPW for day-to-day protection and slickness.