On 31 Aug 2009 08:17:46 GMT, Huge wrote:

On 2009-08-30, Andy Champ wrote:
Calvin Sambrook wrote:
Having spent a "fun" weekend totally stripping down and rebuilding my 20
year old touring bike because the bottom bracket seized... and then I
noticed the wheel axels were stiff... and then I noticed the headset was
tight... I was wondering why grease turns into something resembling glue
after a couple of decades. The bearings were all sitting in quite "tacky"
grease about the consistency of impact adhesive.

The grease I was using to re-lube was Castrol LM, a lithium grease, which
comes in a tub with a cover over the grease with a hole in the middle. You
push the cover down to get some grease up through the hole. I had always
assumed that was simply to keep the unused grease clean but I saw that the
older smears around the top part of the tub (it's at least a decade old!)
looked very similar to the stuff on my bike, no longer flexible and very
tacky whereas the product under the cover was fine so I guess it's
something
to do with reacting to air.

Anyone know what's going on?


At a guess - the volatile components have evaporated.

And the remaining stuff oxidised.

Thence to collect dust and turn into proto-stone.

Derek