Educational Zone #23 – Cosmoline Removal

I had a few folks ask me how to best remove Cosmoline from a firearm. Cosmoline is a Vaseline-type preservative that was used to preserve firearms.

Collectors of C&R (Curio & Relic) firearms often find old firearms that were built around WWI or WWII and then put in storage. These guns were usually just dipped in a big vat of Cosmoline and then put into storage.

Sometimes folks forget what is going on and get all mad at the big Cosmoline mess that must be cleaned up on these old guns. But we ought to remember that Cosmoline is actually our “Friend”.

It has preserved these old guns, like new, under the Cosmoline, and all we have to do is clean them up to have a 50+ year-old, brand new gun. First, let’s look at some pictures of a Yugo SKS that I found at the gun show last weekend.

It is like-new and has a coating of Cosmoline.

Here it is. e23-1 One important thing to remember about Cosmoline is that the guns were “dipped” in a vat of the stuff.

It isn’t just a coating on the exterior, but is in every nook and cranny of the gun.

And it all has to be cleaned out.

Here’s some showing between the stock and barrel assembly. e23-2 Here’s some in the grenade launcher sight. e23-3 And look at this mess on the bolt face. e23-4 And another look. e23-5 It is important to remove the stock and all removable parts to be sure you get all the Cosmoline out of the gun.

This one even had it in the butt stock where the cleaning kit is stored. e23-6 Now, before anyone says it, Yes, I know that many old guns have a lot more Cosmoline on them than mine did. But it was actually worse than the pictures show. The removal method is the same.

There are many ways to remove Cosmoline. Almost all of them work. Some folks like to heat it up, even in an oven on very low heat, to melt it out.

I like to use Mineral Spirits, sometimes simply called Paint Thinner, to remove the gunk. It is available at any paint department and is relatively cheap.

Never, never use gasoline. It is far too flammable and contains lots of really nasty stuff like benzene and other things that you don’t really want in your system. And, mineral spirits work just as well, if not better than gasoline.

As I disassembled the rifle, we really started to find the Cosmoline. Here’s the operating spring, fully loaded with the stuff. e23-7 And look at the mess down in the action. e23-8 At least I didn’t have to worry about rust on this rod. e23-9 Now to get to work on the clean-up.

I put some Mineral Spirits in a plastic pail and started to wash down the parts. 

First, the trigger group.

I just use a cheap paint brush to wash the parts out thoroughly. e23-10 I then use an air compressor to blow any remaining stuff out. 

Keep at it until it is completely clean.

I use an old toothbrush to get at the small areas on the bolt and other areas.

Just keep repeating, “Cosmoline is our friend. Cosmoline is our friend.” e23-11 The sight assembly took some extra work, but came clean. 

Notice how the Mineral Spirits is getting dirty.

When it is too dirty, I just change it and start over with a fresh supply. e23-12 Lastly, I wash the stock.

I bought some “greenie” pads and use this and the Mineral Spirits to clean the stock.

Then wipe it dry and let a fan blow on it for about an hour and it will be totally dry and ready for refinishing.

My buddy Tman lightly sanded the stock.

This particular stock had no valuable cartouches on it, and there was no reason not to lightly sand it.

He then stained it and finally rubbed it down with a satin finish. e23-13 I do not “bleed out” all the oil in the stock. In fact, I’m not sure it is even possible.

I wash it in mineral spirits and then let it dry in the sun for about 30 minutes. It will be so dry that it will have a kind of gray color on the surface. But after finishing it, when it gets hot, it will bleed again.

I know some folks have self-built ovens where they heat up the stock in an attempt to bleed out all the oil. I’ve even heard of guys hanging their stocks in the hot attic in the summer, over a box of cat litter, to get out as much cosmoline and oil as possible.

My experience is that no matter how much you get out, if you shoot it a lot on a hot day, it is going to bleed oil.

An intresting thing I’ve noticed is that even with a poly finish such as I use, the oil will bleed out and I just wipe it off the stock. It doesn’t seem to hurt the finish at all.

You’d think that it would “lift” the poly, but it doesn’t. I just wipe it off. Here’s the finished product, after reassembly. e23-14 And here I am, blazing away with it at the range.

Notice the smoke coming out of the barrel.

It shot great. Not a single failure of any kind. e23-15 Conclusion:
C&R collecting is a great and not-too-expensive hobby. Refinishing these fine old weapons to “better then original” condition is a fun way to spend a weekend.

Give it a try. You’ll enjoy it