"My first large batch, about a pound, burned great for about 3 seconds and then exploded, which is not something thermite is supposed to do. It turns out I should not have used a zinc penny to cover the hole in the bottom of the crucible: The boiling point of zinc is much less than the temperature reached by the reaction, so when the molten iron hit the penny, it exploded into zinc vapor. A copper penny was only slightly less explosive: Turns out you're supposed to use an aluminum disk. Using folded up layers of aluminum foil I have had no more problems with explosions. Which is not to say I'm anywhere closer than 20 feet away whenever I ignite thermite: It would be really quite stupid"
![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png)
timeasmymeasure
no subject
Date: 2008-12-24 06:44 pm (UTC)"My first large batch, about a pound, burned great for about 3 seconds and then exploded, which is not something thermite is supposed to do. It turns out I should not have used a zinc penny to cover the hole in the bottom of the crucible: The boiling point of zinc is much less than the temperature reached by the reaction, so when the molten iron hit the penny, it exploded into zinc vapor. A copper penny was only slightly less explosive: Turns out you're supposed to use an aluminum disk. Using folded up layers of aluminum foil I have had no more problems with explosions. Which is not to say I'm anywhere closer than 20 feet away whenever I ignite thermite: It would be really quite stupid"