Just curious, I got an old 69 B body windshield gasket, it's not rock hard but not like a fresh gasket either. Is there anyway to soften it up, maybe by soaking it in something that softens rubber.

Vaseline softens them up.

Sheldon

Rub it in a few times to soften it up. I haven't tried it for 20 years but it used to work. The gaskets are older now of course.

Sheldon

Dave i hear a couple ounces of wintergreen oil in a pint or so of xylene. The wintergreen is supposed to have a natural plasticizers called meythyl salicylate. I have never tried it myself but this is what the chemist said at the rubber manufacturer i work at.

I will suggest silicone, not any lube that has petroleum in it.
Rubber hardens due to exposure to sun (and petroleum products over time). In it's natural state rubber is white (as why old tires were white). anyone remember those movies in school of the natives pouring latex and rolling big donut wheels of rubber?
the black comes from carbon black added to uv protect the rubber from oxidizing. it still will over time but silicone is the by-product of rubber oxidizing. wind dirt and ran carries it away, the silicone protects and rejuvenates to top few layers.
best thing for protecting it is 100% silicone grease. permatex dielectric grease was one source, dow 33 another but I'd make sure it did not go syn.
smear it on, let it set a day or so then wipe off. repeat occasionally.

If you mean for installation,we once took the gasket for an 84 pickup,threw it in a pot of water on the stove for a bit,and installation was a snap. It was cold as all hell out,and otherwise I doubt we would have successfully installed it.

Palmolive soap and warm water.

I was looking for a new gasket for my convertable a couple years ago when they were back ordered and one of the dealers at mopars in the park told me if gasket was in good shape and not torn, to run it through the dish washer. He said the heat and steam will soften it up. Never tried it cuz I ended up with a new one before I got that far.

was told years ago by some old-timers in the 300 Club to thoroughly clean the gasket then soak it in handcleaner like goop for a week. Seemed to work

Dave,
I'll second Mike's suggestion on the Goop handcleaner. Sounds goofy, but it works.
Chris

A guy I work with just softened some 1966 motorcycle carb boots up with the same thing ademon suggested with the xylene and wintergreen?.. It worked well...Kevin