Questions About Lamination

For your 4 question
-a lamination occurs when the metal for coin blanks is being mixed and it does not mix properly

-yes

-yes, especially in certain series and years, an example of this is the Canadian tombac 5 cents, they were only issued for 2 years durring the war and the mint was under a lot of pressure during the war to make them so a lot of lamination errors occurred because the mint had to pump them out fast,their staff was low,the alloy was hard to mix.

-it depends on how the lamination looks, how big it is and if it ruins the eye appeal of the coin.

More people would understand laminations if they had ever worked with dough making pie crusts or pastries.

In theory the ingot the coinage strip is rolled from should be homogeneous with no bubbles, voids, or foreign matter in it. While foreign matter is rare, it is not that unusual for the metal to have bubbles from dissolved gases that come out of solution during the pouring and casting of the ingots. During rolling these bubbles are flattened, stretched, and broadened. If you could see inside the strip you would see the bubble has forced its way into and through the strip separating it into layers that are either not bonded together or only bonded in a few places. If the bubble is close to the surface it can break through exposing the internal layering and causing surface flaking of layers if they are thin enough.