Use Ramekin cups to freeze ice. They can be found in glass or ceramic and they stack nicely on a cookie sheet. You have to allow for a few minutes of thawing to dump them out to store in a glass bowl. These are the little cups that creme brulee and puddings are made in individual serving sizes. You can purchase them cheaply at a restaurant supplier. I think I paid about $30 for 50 of them.

 

It seems that with all the warnings of plastics that someone would have created an impact-resistant glass reusable ice cube that is partially filled with water to allow expansion for freezing. My daughter and I look for these online every few months and so far nobody has manufactured them! I think it would be a great idea!

 

Pyrex works too

 

Pyrex was the word I was looking for but I could not remember it so I said impact-resistant)

 

Silicone must be okay to use