I've set up a basic glass forge with a small pool of water to freeze the molten glass. But I have to refill the pool periodically.
Looking at the behavior of this water when molten glass falls in, I notice that the amount of water decrease with each packet of molten glass.
As you can see above, there's 87.5 kg before the molten glass packets fall inside the pool.
After that ...
Only 62.5 kg remains.
And no steam around :
87.5 - 62.5 = 25 kg
The forge produce 25 kg of molten glass : 2 packets of 10 kg of molten glass, plus 1 packet of 5 kg
This means that each packet of molten glass, whenn falling into a tile of water, deletes an equivalent amount of water. O_o
Steps to Reproduce
Reproduce the system and look at the water being deleted by molten glass
This issue has not been confirmed by a developer yet.