Your method for degreasing?
 

The other day I tried cold bluing some parts on a 60 year old Colt revolver I've owned since the 50's. It was exposed to a fire, wherein the burning plastic material .....chemical reaction....ruined the blueing in places, almost like rust. After sanding etc., I tried washing in hot soap/water, I tried "degreaser", and soaked in denatured alcohol....... Still I have places 'in the white' where the blue just wouldn't 'take'. So, I'm asking for your favorite method of getting steel clean. Bill

Try cleaning with MEK.

I've had good luck for many years using automotive brake cleaner available at any auto supply store. This product behaves exactly like carbon tetrachloride and dries in just a few moments leaving no residue whatsoever. Care must be taken not to get this product on paint or plastic as it will damage it immediately. I've used it to clean bores with great success also. IMO, this is the best degreaser available. Personally, I've never had it cause damage to any type of bluing. Its highly flammable so if you try it use caution!

Many types of soap contain moisturizers, and this might be the reason why your bluing didn't take. Some people use the cheapest dish soap they can find just to avoid moisturizers and different smell-good additives that can affect the finish.

Solvents like paint thinner and acetone work, as long as you keep it clean. If you dunk the parts you'll dissolve the oil in the solvent, and some of this will still be on the part when you pick it up. Same thing if you wipe it with a rag, you'll have to use several clean rags with solvent before it's really clean.

I have had mixed results using brake cleaner. Some (like Brakleen brand) work great, while some seem to leave residue of some kind. My favorite degreaser is scrubbing with Purple Power and then a thorough rinse under the hot water tap, it's the best method I have found so far.

Another option is to use Brownells Oxpho Blue, it works on oily surfaces and also seems to hold up better than other brands. As an added bonus, it doesn't have that nasty cold blue smell to it. If you don't want to order it from Brownells you can call S&R Guns in Algood (931-537 6862), they had it in stock last time I was there.

Boiling water?

Jerry I have used boiling water on magazines and other things, melts all the grease right off the pot, then throw the pot in the dishwasher or make sure you clean it extra well.

I used to work in the lab at a refinery many years ago, and hot water was actually the best way to clean the thick, gooey pitch oil out of bottles and test tubes. I use it sometimes when I have to deal with more massive amounts of gunk, just like Ed says it will soften the hardened deposits and make them easier to scrub off. Solvents (for example acetone) seem to have the opposite effect sometimes, it can dry out old goo and turn it into a hard crust that sticks even worse.

I had a discussion with a guy who works with metal plating (which requires a 101% clean surface) and he used steaming hot water with a squirt of cheap dish detergent for the final cleaning. Then he rinsed in hot tap water immediately to get the residue off. The parts were so clean that he had to carry them in a pail of water to keep them from flash rusting during the short trip from the sink to the pickle bath. He had to wear mittens inside rubber gloves, but he said that it works great. I'm sure it does, but it's probably overkill for bluing purposes.

In this case it seems to be a matter of just a very thin film of something, so a good degreaser and a rinse in hot water should suffice. Now when I think about it, another cause of the problem could be the fire. Hardened steel is usually more difficult to blue than softer steel, and it's quite possible that the fire made the hardness uneven enough to show in the bluing.

I have had good luck scrubbing with Simple Green and hot water. I have also had good luck scrubbing with acetone (using heavy chemical resistant gloves).

I had good luck removing some stuff that was like sap from a 1942 Hipower using Kerosene.

It was on very thing even the hammer pin.

When I got done it functioned as smooth as a babies behind.

Bingo! Spray carb cleaner. It's mostly acetone and/or MEK.
Yeah, even cuts through horrible, petrified Soviet cosmoline with ease!