Paper Ingredients That Expand Under Certain Soaking Conditions!?

Recently when soaking/cleaning some used stamps - using hot water and some kitchen salt hoping to get off dirty remnants of gum, hinges etc. I was left over with stamps that showed things like this:





I referred to it as "galls" [but not caused by wasps!] Both stamps are Dutch of the 1953 period...

And today I nnoticed hat several of my "Germania" stamps I meant to clean up showed a similar thing.

You can easily "feel" the "galls"!

I've not seen this before. Are you sure that they aren't salt deposits? (You might want to taste them?) Perhaps the salt is crystalizing onto some parts of the stamp as is dries?
Don

Perhaps the salt is reacting with some ingredient of the paper. Have you experimented using both a saline and distilled water soak on stamps with the same paper?

I've never heard of using salt as a cleaner. Soak those stamps in clean water. Some people use one or two drops of detergent in the water, but I haven't tried that.

Robert

Some papers, especially early papers, were not made of 100% cellulose (wood) pulp; they contained natural fibers like wool, cotton, hemp and even silk. I believe what you are seeing is a reaction to the hot water and salt. Wool will shrink when immersed into hot water. Wool ends also have a tendency to "pill". If you don't believe me, ask your wives, girlfriends, significant-others, or dry cleaners what happens if they mistakenly wash wool sweaters or pants the wrong way. I also believe you are seeing fiber shrinkage plus an alkaline-reaction of salt locking into the natural fiber and causing it to expand when it dried. You are also seeing an ink reaction (in the blue and yellow stamps) to the hot water and salt mixture called bleeding. Hot water should never be used to soak stamps; tepid water is recommended to avoid ink bleeding and fading, of the type seen in these images.

Happy 4th of July weekend everyone!
Hal