Ice at 32o is not the same as sub-zero ice. Ice at 32o is confronting the reality of becoming liquid. It’s sweating. Ice shouldn’t sweat. Good ice is dry. Also consider quality cooler packs like Arctic Ice; very beneficial for ice retention. One of the best ways to test is the sticky test. If the bag of ice tends to stick to your moist hands, thats a good sign. If it does not stick much and seems rounded, clearer and melting… not so good. Find a supplier near you who has the best/coldest ice for best retention.