View Full Version : OT? softening rubber

09-06-2011, 02:06 PM
I have a filler spout for a WWII Jerry can. It has the lever that squeezes a rubber sleeve to expand it to fit snug in the can opening.

I did a google for what to use to soften the rubber since I can't seem to find a replacement. Kerosene seemed to be mentioned most often so I have had it soaking for about 5 days now and it has gone from hard as a rock to slightly flexable. At this rate it may take months to get it pliable and serviceable again. I probably can find some rubber to machine a new one and may have to.

Does anyone have experience softening old hard rubber parts and what have you used? Did it work?

09-06-2011, 02:25 PM
Most of the stuff (solvents) that will soften aged, hardened rubber usually also speed up the decomposition process.
Your better off replacing the rubber.

383 240z
09-06-2011, 02:58 PM
Those spouts are for sale all over the place. http://compare.ebay.com/like/200632583651 http://www.armysurplusworld.com/product.asp?ProductID=50086

09-06-2011, 04:45 PM
Yeah, but this spout is an an ti qu aka, antique, and I want to keep it. I guess I'll make a trip to the local rubber supply store in Louseyville Ky.

I'll leave it soak until it's soft enough or melts, which ever comes first and yes, solvents speed up deterioration. It's just an experiment right now.

Just wondering what others have done.

09-06-2011, 05:03 PM
I have a filler spout for a WWII Jerry can. It has the lever that squeezes a rubber sleeve to expand it to fit snug in the can opening.

this sounds like the old style plugs for thermos jugs, and i had one for the drain for a small fishing boat. . . that might be a place to look. . .

09-06-2011, 05:57 PM
Many years ago I read a book by James Melton, a famous opera singer and antique car collector, in which he describes his struggle to find the correct tires for some very rare car. He finally found them, hard as a rock, and the solution he or his consultants came up with was to weight them down and throw them in a lake for a few months. Apparently this softened them up, and they were good as new. Might be worth a try!

09-06-2011, 06:26 PM
sometimes ..in a brake overhaul kit is a packet of grease called rubber grease

also the grease inside of a steering rack is of the sort that is kind to rubber .

other than that i don't know

other than silicone spray.

all the best.markj

09-06-2011, 07:44 PM
I have heard of running wiring harnesses through a dishwasher with the detergent to soften them. might want to wait till the better half is away for a bit :D

09-06-2011, 08:34 PM
Here are a few methods others have tried...http://www.motorsforum.com/studebaker/Rejuvenating-Rubber-17205-.htm

Grind Hard
09-06-2011, 08:48 PM
My friend who owns a rubber company has this advice:

"You need to know what sort of rubber you have.

See there are about 150 kinds of rubber... tens thousands of fillers modifiers and additives. Each combination requires a different cure agent.

Given that it's WW2 vintage... and that it's NOT latex... it's ether Ameripol or GRS. My money is on GRS. (Government Rubber: styrene)

Knowing this you can look up what solvents you need to rejuvenate said polymer."

09-06-2011, 08:52 PM
Try doing a "Google" for rubber rejuvenator.

It's supposed to restore the "suppleness" & flexibility of the rubber.

09-06-2011, 08:54 PM
I used to use a product called rubber renew for pinch rollers, etc. Electronics suppliers might still have it- I think it's one of the GC or MG chemicals products. It's a foul smelling liquid, but it works. Something to be done outside, if there's any size to the part.

Don Young
09-06-2011, 09:16 PM
If you want something suitable to make a replacement from, look in a good plumbing supply store for expandable rubber "test plugs". They are used to seal drain pipes for leak testing.

09-06-2011, 09:29 PM
silicone oil works great. Be careful with the sprays. Many of the sprays use a solvent to deliver the oil and that can harm the rubber.

09-06-2011, 10:50 PM
I have used dot 3 brake fluid with some luck.Seems it has a ingredient to keep the rubber parts flexable.

09-06-2011, 11:32 PM
Soaking the rubber or polymer part in methanol swells most of them . It may or may not stay swelled after it dries out. I've also used lacquer thinner to enlarge O rings used to seal carburetor float chambers. Often the O rings are too small to fit the groove , so I enlarge them until they fit, and then quickly assemble the carburetor.

J Tiers
09-07-2011, 09:02 AM
Rubbers are a polymer, similar to many "plastics". They are long chain molecules with a certain amount of crosslinking to form a solid, but sufficiently non-linked to be flexible.

Rubber can "age" by the escape of a plasticizer, or by the chemical structure changing. Long chain molecules can get "crosslinked" where they used to be separate, etc. That is common with natural rubbers when attacked by ozone.

Polymers can "age" by the "plasticizer" compound (if one is used) escaping, which is why some plastics harden and get a sticky coating with age, and why the inside of car windows picks up a slime. The plasticizer can be looked at as a sort of "lube" for the long molecules, allowing the "tangled" molecules to slip past each other to some degree.

When it is no longer present, the material is harder and less flexible.

In neither case is it really practically possible to reverse the process.

Some rubbers, such as EPDM are very stable as far as standard "weathering", others are not.

09-07-2011, 01:19 PM
Here's my suggestion