Let me preface this by saying that when the rules don't even come close to addressing something we use real world physics to help determine what would happen. Water is its most dense when in its liquid form, extra fact we looked up for relevance here. pressure causes an increase in temperature as well.
One of my players asks me if they can purchase 2 scrolls of permanency, i let them since they would be available where they are. He then later asks about getting some graphite. I get suspicions and ask him what he is trying to do. so he lays out his plan.
1. cast force chest (spc 97)
2. use scroll to permanence it. i decided i would let this work since it isn't explicitly on the list.
3. fill chest with water.
4. cast shrink item on the water itself
5. permanence the shrink item, explicitly stated it can be shrunk and expanded at caster command.
6 add more water to chest, as well as some of the graphite.
7. close chest and let shrunk water expand.
8. let the intense pressure build up and cause heat eventually turning the graphite into a diamond.
this was just too creative so i had to let it happen. i just can't let pure carbon be too readily available in my game now.