Leather with smallpocs

[MadsH]

Hello all

I got an question someone in here might know the answer to.  At a Danish leatherpage a guy made a bag and appearently had it out in some slight rain and the leather popped as if it had smallpocs. It does not dissappear again when dry.

None at the page had ever seen it before and the question is why it happened.  Several ideas came up but none seems reliable. My thoughts are the leather and the leathercells might have been damage during preparation at the factory but I really dont know. The guy tells it was pressed veg. leather The guy made a small reel to show and the link is here :https://www.facebook.com/reel/720066986998380/?group_id=1550075015207584&s=group&__cft__[0]=AZUEGAycQE4v6J7z7i9XRy-u7_LRr-UcJgG-0hGcT0-RFw6ff1OIwdPoJJ0O7HKzf6B8424B8lTGUh8TIitmfnDugOMg3U9MyoKavxfRtu1sswbi_2bvXqpHURofu7ULiQ0-4TiUsWMfkQzIvlH7EF_v1eghlMCvaHKKCiCjdKbDjIXrjbNhkZauLR3Mlwya_PN2FEJeH9jjeqKI8YP9Q8ii&__tn__=H-R

Does anyone in here have a good answer ? 

[TomE]

The link didn't work so I couldn't see the defect, but it sounds like lifting of the grain.  There is a natural junction between the grain and the underlying flesh layer (corium) that is rather weak and open in structure.  It is vunerable to breaking and more so in low quality leather, a defect referred to as "looseness."  The "break" of the leather refers to the ripples created when the grain is sharply flexed (concavity).  Good quality leather makes fine ripples (fine break) and low quality leather makes coarse ripples with more separation of grain and flesh layers.  Blistering caused by uneven wetting of the leather is the same phenomenon.  If you're interested in the structure and chemistry of leather the book "Tanning Chemistry. The Science of Leather" by Covington and Wise is a very detailed (685 pp) reference.

[Northmount]

9 hours ago, MadsH said:

The guy made a small reel to show and the link is here

Nothing loads here either.

[MadsH]

Hmm strange, it opens to me, unfortunately the guy didnt post single pictures but only the reel.  But anyway ... It seems my guess why, more or less :-) was right. 

12 hours ago, TomE said:

The link didn't work so I couldn't see the defect, but it sounds like lifting of the grain.  There is a natural junction between the grain and the underlying flesh layer (corium) that is rather weak and open in structure.  It is vunerable to breaking and more so in low quality leather, a defect referred to as "looseness."  The "break" of the leather refers to the ripples created when the grain is sharply flexed (concavity).  Good quality leather makes fine ripples (fine break) and low quality leather makes coarse ripples with more separation of grain and flesh layers.  Blistering caused by uneven wetting of the leather is the same phenomenon.  If you're interested in the structure and chemistry of leather the book "Tanning Chemistry. The Science of Leather" by Covington and Wise is a very detailed (685 pp) reference.

Thx for the comment and the referance for the book.