I made my ice cube keeper out of foam, fabric, paper, and a cup.  I predict that my keeper will protect the ice cube for 360 minutes.  First, I put foam across the top of a large red cup.  I covered the top of the foam with fabric scraps and string, and I taped everything.  I put the ice in the cup at 10:00.

Time	Size in mm
10:00	45mm
11:00	35mm
12:00	2mm
1:00	0mm
2:00	0mm
3:00	0mm

After looking, I think that my prediction is now 120 minutes.  Gone!

If I were going to make another ice cube keeper, I would wish I didn’t have to open it to check on the ice cube and let the heat in.  Maybe a see-through cup to protect it so I could still measure it.