You can lose some materials by turning them into a block form and back with a full inventory. You can lose 8 ingots from the 8 iron blocks this way.

How:
1. Fill inventory with any item except iron ingots except one slot with 8 iron blocks.
2. Go into survival and put the 8 iron blocks in the crafting grid to make iron ingots.
3. Shift+Click the iron ingots into your inventory and you will get 64 iron ingots even though 8 * 9 = 72.