Thanks for the question! I meant to say that crystals will form on the containers as well as the strings and to better observe crystal growth on the strings it is preferable that they don’t grow on the container, therefore glass is preferred. I’ll fix this statement- it is confusing!

Tips
◦We found that crystals were more likely to grow on plastic containers than glass containers, making if preferable to use glass jars when possible so you can easily observe the crystal growth. If you do use a plastic jar/container make sure that it can withstand the heat of boiling water and will not melt/deform.

You say the crystals are more likely to grow on plastic containers, but them o on to recommend glass ones. Or do I misunderstand you ?

Many thanks for your wonderful articles.
Marilyn.