Degrease the basin and beater of a food processor using lemon juice.
Beat the egg whites until they are white and fluffy.
Gradually add the granulated sugar while beating, then continue beating for about 10 minutes. The mixture should form soft peaks.
Add the icing sugar and beat for a short time. The egg white mixture should now form stiff peaks.
Press the balloons into the egg white and adjust using a palette knife if necessary.
Hang the balloons from pegs on the oven rack and dry them at 70°C with the fan on a low setting (otherwise, the balloons will swing) for 4 hours until dry.
Puncture the balloons and carefully remove them.
Store the meringue in a well-sealed tin with silica beads.