Why did this grease turn to glue?

I have an old (1935) Kitchen Aid mixer that needed re-greasing about 15 years ago. I could tell because it was having a hard time starting
up. So I took it apart and cleaned every last trace of the dried out old grease out. It looked like it was probably originally white lithium base grease so that's what I used when I re-greased it. A few months ago it started acting again like the grease was getting too stiff. This time the grease turned into glue. I took the gearbox apart and tried washing the grease out with stoddard solvent and the solvent hardly touches the stuff. It has to be removed with a stiff brush. Anyway, I got most of the grease out and have been looking for a good grease to put back into the gearbox. I ordered some food safe grease and today decided to wash the last traces of the old grease out but I cannot get the transmission to come completely apart now because a couple shafts refuse to turn and they need to be turned so I can get at a retaining pin. I stick a 5/32 allen wrench through a pin hole in the output shaft to turn it and the allen wrench bent. The shaft still won't turn. What could cause this grease to do what it did? Thanks, Eric
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snipped-for-privacy@whidbey.com fired this volley in

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
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On Fri, 18 Sep 2015 18:07:54 -0500, Lloyd E. Sponenburgh wrote:

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.
--

Tim Wescott
Wescott Design Services
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On Fri, 18 Sep 2015 21:00:50 -0500, Tim Wescott

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.
--
Ed Huntress

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On Sat, 19 Sep 2015 10:18:18 -0400, Ed Huntress wrote:

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.
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wrote:

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

--
Ed Huntress

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On Sat, 19 Sep 2015 10:18:18 -0400, Ed Huntress

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
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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
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On Sat, 19 Sep 2015 12:23:50 -0500, "Lloyd E. Sponenburgh"

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.
--
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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
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On Sat, 19 Sep 2015 13:09:40 -0500, "Lloyd E. Sponenburgh"

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.
--
Ed Huntress

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Hot and breaks down some bonds, activating motion in others.
Good idea. Likely why some RF vibration tanks have heaters inside. Mine does.
Martin
On 9/19/2015 1:21 PM, Ed Huntress wrote:

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Acetone can also help.
Joe Gwinn
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As can Naptha.
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wrote:

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
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On Sat, 19 Sep 2015 10:02:35 -0700, snipped-for-privacy@whidbey.com wrote:

I don't know what you're got there, but I'd try gasoline.
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How about brake or transmission fluid ?
Martin
On 9/19/2015 12:02 PM, snipped-for-privacy@whidbey.com wrote:

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