If I wet a piece of paper and put it down on another piece of paper it will stick (a little bit) to it. What are the forces involved here (surface tension maybe)? What would be the strength required to separate them again?

PS: It seems to me that the main responsible for this adhesion would be surface energy/surface tension. But I am lacking some values for the surface tensions involved.

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    $\begingroup$ It just wets the glue on the stamp/flap, which then sticks and re-dries. If you stuck lots of stamps regularly, you got a little sponge to use rather than licking them. $\endgroup$
    – Jon Custer
    Aug 5 '16 at 18:29
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    $\begingroup$ I'm voting to close this question as off-topic because it is about chemistry, not physics. $\endgroup$ Aug 5 '16 at 21:55
  • $\begingroup$ So THAT'S why my tongue sticks to the roof of my mouth! ;-) $\endgroup$ Aug 6 '16 at 2:48
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    $\begingroup$ The revised question removes references to glue and is more about surface tension than chemical reactions; vote to reopen. $\endgroup$
    – rob
    Aug 6 '16 at 16:16
  • $\begingroup$ It still concerns saliva rather than water. Is the stickiness due to something glue-like in the saliva? Or is it due to the physical properties of water? It would be much clearer if you replaced "lick" with "wet" : "If I WET a piece of paper..." $\endgroup$ Aug 6 '16 at 16:21

From Postage Stamp Glue

The appearance of the gum varies with the type and method of application, and may range from nearly invisible to dark brown globs. Types of gum used on stamps include:

  1. dextrin, produced by heating starch

  2. gum arabic or acacia gum, derived from the acacia plant

  3. glue, from gelatin, rarely seen on stamps

  4. polyvinyl alcohol

I think the actual process's of salvia plus glue equal sticky is more of a ChemistrySE question, but the Wikipedia article sticks (sorry) mainly to methods of attaching stamps.

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    $\begingroup$ without going into chemistry (I modified the question to make it less chemistry oriented) couldn't some forces such as surface tension be involved? $\endgroup$ Aug 6 '16 at 15:13
  • $\begingroup$ First, don't cross post, someone will shout at you :) Here is the full story behind adhesion, told in excruciating detail. I don't think surface tension is involved though. en.m.wikipedia.org/wiki/Adhesion $\endgroup$
    – user108787
    Aug 6 '16 at 15:19
  • $\begingroup$ @AlbertBeton no problem, I hate licking stamps and envelopes. $\endgroup$
    – user108787
    Aug 6 '16 at 15:32

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