A small batch of royal icing with the consistency that is perfect for piping minor details onto macarons.
Add 1-2 tsp of water to the dry mixture and stir with a spatula to get the mixture going. If it's still lumpy, add another 1 tsp of water and stir again.
With the spray bottle, slowly spritz water onto the mixture until it reaches the proper consistency of a "15 second" icing. When a knife cuts through the icing, it will take 15 second for the cut to disappear.
If it's still too thick, spritz more water. If it's too runny, add more icing sugar.
Optional: Split up the icing and add gel food color to the mixture and mix gently until fully incorporated.