Molten glass per bucket of sand:
2 giant seaweed, 12 sand - ~1.45 molten glass per sand
3 giant seaweed, 18 sand (without picking up) - ~1.49 molten glass per sand
3 giant seaweed, 18 sand (picking up glass) - ~1.6 molten glass per sand

Molten glass per giant seaweed:
2 giant seaweed, 12 sand - ~8.7 molten glass per giant seaweed
3 giant seaweed, 18 sand (without picking up) - ~8.9 molten glass per giant seaweed
3 giant seaweed, 18 sand (picking up glass) - ~9.6 molten glass per giant seaweed

Crafting xp per giant seaweed:
2 giant seaweed, 12 sand - 538.5 to 669 xp per giant seaweed
3 giant seaweed, 18 sand (without picking up) - 551 to 685 xp per giant seaweed
3 giant seaweed, 18 sand (picking up glass) - 588 to 732 xp per giant seaweed

This calculator assumes the player will use Superglass Make and blow the molten glass into the selected item.

Superglass Make is cast once per inventory.