One of the easiest ways to build a model igloo is to use sugar cubes. Sugar cube igloos not only make for good examples for school projects, they also make for excellent winter season decorations. Even if you live in an area where the only snow you see in winter is on TV, a model igloo can give you that feeling of walking in a winter wonderland.
Place the foundation layer of sugar cubes down around the edge of the cardboard circle. Make sure to leave a gap in the circle to allow for the entrance.
Combine three cups of confectioners' sugar with two egg whites in a small bowl and mix thoroughly to make the mortar.
Apply a small amount of mortar to the bottom of the first sugar cube in the second layer. Place the cube on the foundation layer so that it is centred on top of two of the foundation layer cubes. Make sure that the cube is slightly closer to the centre of the cardboard circle than the foundation layer to will allow you to reduce the circumference of each subsequent layer.
Continue to add sugar cubes until you have built five levels. Set the igloo aside and allow it to completely dry when five levels have been completed. Add the next five levels once the igloo has dried.
Build the roof. Start with a single cube on a flat surface and mortar cubes around the centre cube until you have a circle large enough to cover the top of your igloo. Set the roof aside and allow it to dry completely. Use white craft glue instead of mortar for a stronger hold on the roof.
Build the arch. Line up sugar cubes into the shape of an upside-down "U". Mortar a second layer of cubes on top of the first layer and set the arch aside to dry completely.
Mortar the roof and arch to your igloo and set it aside to allow it to dry completely; white craft glue can also be used for a stronger hold. Decorate your dry igloo with icing sugar, white frosting, shredded coconut or marshmallow snowmen: Your imagination is the limit.
Because of the use of raw egg whites, it is not recommended that the igloo be eaten.