What type of staining is this ? 0

[Lamborghinikid]

Is the water , or just the page turning from age ? Expertise always welcome.

[KobaltDog]

Looks like a liquid stain

[Dick Pontoon]

Yup, it does.

[Lamborghinikid]

Thank you 

[Bomber-Bob]

Those look like tide lines to me = stains. 

[joeypost]

Damage by water. Some cases tide lines, in other areas it cleaned the tanning from the page resulting in the whiter areas in the back cover. 

[JollyComics]

That is pretty common.

Drink while reading the comic book.

Spill while water or drink oozing the comic book.

That is how it got water/drink stain.

[The Lions Den]

Classic water stains...

[Ze-man]

On 10/20/2018 at 8:10 AM, joeypost said:

Damage by water. Some cases tide lines, in other areas it cleaned the tanning from the page resulting in the whiter areas in the back cover. 

As well as washed off the kaolin clay on the surface leaving behind a rough surface.  On SA books like this I always preferred to call this water damage , rather then a water stain.