Cited from http://www.ehow.com/list_5931700_materials-insulate-ice_.html &
http://www.ehow.com/list_6871445_materials-cubes-melting-longest-time_.html, we found this:
"Sawdust
One of the oldest ways to insulate ice is to coat it with layers of sawdust. This method was used in ice houses and even in ice boxes as recently as the early 1900s. Ice that was brought into an ice house during the winter months could be kept cold and insulated well into the summer by making sure it was laid aside and properly coated with sawdust. A sheet or some other material would be placed between the ice and the sawdust, so that the ice could still be used to keep food and drink cold without contamination.
Styrofoam
Styrofoam, or polystyrene as this type of plastic is called, also does a good job insulating ice. Developed during the scientific advances made during World War II, polystyrene is a light plastic material that doesn't transfer heat very easily. That means that if ice is kept in a polystyrene container (such as a cooler), the heat from the outside of the container isn't easily transferred to the ice on the inside of the container. That allows the ice to stay away from the heat for longer periods of time, and thus to stay frozen longer.
Air
Surprising as it may sound, air is also a good insulator for ice. That doesn't mean that you should leave ice totally exposed to the elements, though. What it means is that if you trap cold air into a container in a way that it surrounds the ice (such as using a pressurized, plastic container that can be filled with air), it will provide a secondary layer of insulation around the ice. Then heat will not only have to penetrate the outer layer of material (whatever the container is made of) but also the air inside the container. This approach works best in air tight containers such as those used to contain medical supplies.
Felt
Felt might come as a surprise because of its warm and fuzzy feel, but this quality is actually what makes it an ideal choice for insulating ice. Felt keeps ice from melting because it acts as a natural insulator. It keeps the warm air out and allows the ice cubes to survive for a long time compared to other materials. It also acts to contain the cold air that the ice cube produces, allowing it to continually cool itself off. By wrapping your ice cubes in felt, you give them the longest amount of survival time outside of the freezer.
Newspaper
Newspaper is another good choice, although it is not as effective as felt. Newspaper works in the same way as the felt by acting as an insulator to the ice. Wrap the ice cubes in as many layers of newspaper as you can to provide it with the thickest amount of insulation. Like the felt, the thickness of the newspaper will serve to keep the warm air out and the cold air in, so the ice cube will be able to
last for a little while.
Wool
The thickness of wool allows it to insulate the ice cubes as well as the felt. The same principle applies here that applies with the other two materials; anything that can keep the air out will give the ice a chance to survive. Wool works because it is a poor conductor, which means that it does not transfer energy well. An example of something that transfers energy is metal, which is why metal is used for pipes in homes and for electricity. Wool cannot transfer energy, so any energy that enters wool will simply be trapped inside as opposed to passing through. When it comes to ice cubes, this is a good thing because any heat energy that tries to pass through will simply get stuck in the wool, keeping the ice safe."
One of the oldest ways to insulate ice is to coat it with layers of sawdust. This method was used in ice houses and even in ice boxes as recently as the early 1900s. Ice that was brought into an ice house during the winter months could be kept cold and insulated well into the summer by making sure it was laid aside and properly coated with sawdust. A sheet or some other material would be placed between the ice and the sawdust, so that the ice could still be used to keep food and drink cold without contamination.
Styrofoam
Styrofoam, or polystyrene as this type of plastic is called, also does a good job insulating ice. Developed during the scientific advances made during World War II, polystyrene is a light plastic material that doesn't transfer heat very easily. That means that if ice is kept in a polystyrene container (such as a cooler), the heat from the outside of the container isn't easily transferred to the ice on the inside of the container. That allows the ice to stay away from the heat for longer periods of time, and thus to stay frozen longer.
Air
Surprising as it may sound, air is also a good insulator for ice. That doesn't mean that you should leave ice totally exposed to the elements, though. What it means is that if you trap cold air into a container in a way that it surrounds the ice (such as using a pressurized, plastic container that can be filled with air), it will provide a secondary layer of insulation around the ice. Then heat will not only have to penetrate the outer layer of material (whatever the container is made of) but also the air inside the container. This approach works best in air tight containers such as those used to contain medical supplies.
Felt
Felt might come as a surprise because of its warm and fuzzy feel, but this quality is actually what makes it an ideal choice for insulating ice. Felt keeps ice from melting because it acts as a natural insulator. It keeps the warm air out and allows the ice cubes to survive for a long time compared to other materials. It also acts to contain the cold air that the ice cube produces, allowing it to continually cool itself off. By wrapping your ice cubes in felt, you give them the longest amount of survival time outside of the freezer.
Newspaper
Newspaper is another good choice, although it is not as effective as felt. Newspaper works in the same way as the felt by acting as an insulator to the ice. Wrap the ice cubes in as many layers of newspaper as you can to provide it with the thickest amount of insulation. Like the felt, the thickness of the newspaper will serve to keep the warm air out and the cold air in, so the ice cube will be able to
last for a little while.
Wool
The thickness of wool allows it to insulate the ice cubes as well as the felt. The same principle applies here that applies with the other two materials; anything that can keep the air out will give the ice a chance to survive. Wool works because it is a poor conductor, which means that it does not transfer energy well. An example of something that transfers energy is metal, which is why metal is used for pipes in homes and for electricity. Wool cannot transfer energy, so any energy that enters wool will simply be trapped inside as opposed to passing through. When it comes to ice cubes, this is a good thing because any heat energy that tries to pass through will simply get stuck in the wool, keeping the ice safe."