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The Best Insulators to Keep Water Hot

The correct insulating materials will keep liquid hot for long periods, whether it's for the water boiler at home or a flask of coffee. Bad insulators, or conductors, let heat fade quickly. Examples of bad heat insulators include metals such as copper and steel, commonly used for radiators which are designed to radiate heat. There are a range of materials that can be used as insulators for hot water, each with their own application.

Fiberglass
- Fiberglass is made from strands of glass woven together to make a kind of fabric.The air pockets between the fibers make it hard for heat to escape. This material is commonly found in attic insulation, but is also used to keep water hot in the home. Pipes and older boilers used fiberglass jackets to keep heat from escaping.
Foam Insulation
- Foam insulation is made from extruded polymer plastic derived from crude oil. It is used in the same applications as fiberglass for keeping water hot, although it is more commonly found on pipe work. It insulates in much the same way by containing heat through the use of air pockets in the material.
Thermal Flask
- Anybody who has been camping or hiking will know the value of a good-quality thermal flask to keep tea, coffee or drinking chocolate hot. The principle for this is simple: There are two bottles inside the flask made from metals or glass which reflect the heat back into the flask. The two layers are separated by a partial vacuum through which heat cannot pass. The solid walls of the flask can also be coated to make it even more efficient.
Styrofoam
- Styrofoam is made in a similar way to foam insulation, but is used for making beverage containers. The insulating effect is caused by the same principle of air pockets in the material. This is why the paper cups have been replaced by Styrofoam at many outdoor events and take-out restaurants. The insulating effect from Styrofoam does not last as long as with thermal flasks as there is no stopper preventing the heat escaping.
Other Materials
- Any good insulator will keep water hot given the right conditions. Ceramics, for example, are used to make coffee mugs as the material is a relatively good insulator. Corrugated cardboard is used by many coffee shops as the air pockets encased by the cardstock hold in the heat. This also serves another purpose by not transferring the heat of the drink to the holders hand and so protecting the customer from burns. Likewise, glass was originally used in thermal flasks and coffee percolators.

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