Why did this grease turn to glue?

snipped-for-privacy@whidbey.com fired this volley in news: snipped-for-privacy@4ax.com:

Soap. Most 'greases' are suspensions of an oil in a soap. Once the oil has evaporated or been expelled by heat, the soap congeals and finally dries and hardens.

And soap is NOT soluble in mineral spirits. Water would likely have cleaned it up faster.

Lloyd

Caviat: this is based on theory, not experience.

It may not be too late. Try soaking in hot water, or even boiling it. A bit of dishwashing detergent in the mix might cut through any solvents left in there.

The"soap" used in greases is metallic soap. It is not what we generally think of as "soap" and it doesn't behave like soaps we use in other contexts. Typically it is made from metal compounds reacted with acid, not with fats reacted with alkali, like the soaps we're familiar with, and it isn't generally water soluble.

There are several metal soaps used in greases and they behave differently, but they're all difficult to dissolve. Some, like lithium soap, are slightly soluble in water. Most are not.

They aren't soluble in most common solvents, either. You can try propylene glycol or even antifreeze and see if it works. It will chemically attack a few of the metallic soaps.

Otherwise, I have had success in the past using gasoline to dissolve the gunk from ancient lithium grease (white grease). Maybe it depends on how hard the grease has become, and how much petroleum-based oil still remains in it. I suspect, but don't know, that I had success with that because there was enough oil left in it to take the soap with it when the oil was diluted with the gasoline.

Acetone can also help.

Joe Gwinn

I was thinking that the heat would loosen things up as much as anything. But yes, I shouldn't be thinking "soap = water soluable", particularly when you're talking about grease.

As can Naptha.

Yeah, well, maybe it will. I haven't tried it.

I last night put the planetary assembly part of the mixer into a jar with acetone and shook it up. No dissolving. This morning the grease has still not dissolved in the acetone. Break Free brand penetrating oil does dissolve the old grease. Slowly. Eric

The strange thing about this grease is that it did not dry out like the old grease did. It instead turned into very sticky paste. There was no evidence of free oil like I have seen many times when grease starts to break down. Eric

I don't know what you're got there, but I'd try gasoline.

Ed Huntress fired this volley in news: snipped-for-privacy@4ax.com:

Sorry... that's not even close, Ed. Even the soap you use in your bathroom is a "metallic soap", unless you don't include sodium or potassium in your list of metallic elements.

Bath soap is usually a strongly alkaline substance like sodium or potassium hydroxide mixed with animal fat or vegetable fat, then allowed to 'saponify' (turn to soap, in English).

The soaps for lubricating greases are strongly alkaline substances (like lithium hydroxide) mixed with FATTY ACIDS (that is NOT an 'acid' like you cite... you'd make folks think sulfuric or nitric or hydrochloric). They typically use stearine. But guess what? Sterine is a room-temperature- solid fatty acid derived from pork fat or beef fat.

The fatty acid will react to form the 'lipid tail' with an alkaline 'head' -- JUST like bath soap. The tail attracts oils, the head water. So it can emulsify oily things into a water suspension -- not actually a 'solution'.

So, in all, the soaps used to make lubricating greases are JUST like bath soap, except for their choice of alkali metal salts that are non- corrosive.

Lloyd

Except that most of the metallic soaps used in greases and dryers are not water-soluble, regardless of how you want to describe the chemistry.

The key point is that they don't behave at all like the water-soluble bath soaps and other soaps we're familiar with. Lithium soap is slightly water-soluble, but most others are not.

Ed Huntress fired this volley in news: snipped-for-privacy@4ax.com:

I agree with your solubility claim, but that is NOT the 'key point'. The key point is you completely mis-represented the chemistry to people who may not all be chemists (or empirical ones).

There's a reason auto machine shops use hot steam washers to remove grease. Think about that.

Lloyd

It's the key point in this discussion, because the OP is looking for ways to dissolve the crud. One suggestion involved water. That's why I posted that comment about how metallic soaps are different from bath soaps.

Well, I won't argue it, because I'm not a chemistry guy. That's how it's been described to me by lubricating companies. They make a big point of the fact that the metallic soaps, at least the ones used to thicken grease, are very different from the soaps we're familiar with. Some are stringy, like in wheel-bearing grease; others are smooth; most are insoluble in water.

Steam is hot, for starters.

Hot and breaks down some bonds, activating motion in others.

Good idea. Likely why some RF vibration tanks have heaters inside. Mine does.

Mart> >

How about brake or transmission fluid ?

Mart> >