Since i got to watch a lot of Laserdiscs recently, I felt when handling them that they did not had the same weight between each other, so to verify it I used a balance on some of them and found out that yes, they all have different weights. the lightest i found was around 200g (0.44 lb) and the heaviest I found was around 350g (0.77 lb).

So I was wondering, what causes the differences in weights between two discs ?
Is there a technical reason for some discs to be lighter and others heavier ?

It depends on the manufacturer, same principles but different processes used resulting in the differences.

Off the top of my head SCOTCH 3M LDs were a bit heavier than most & SONY US DADC Lds a bit lighter.

Cheers

I see, thanks for the reply