Sieve the Sodium Bicarbonate and the Citric Acid into a bowl and mix thoroughly until you have a consistent texture.
Add a few drops of the colour and blend through the mixture so that it is even, with no concentrated colour areas.
Add the essential oils into the mixture. Certain oils may start the mixture to fizz, so work quickly. Do not leave the mixture to stand or it may start to set hard.
Use a little Witch Hazel Water in a plant mister and spray VERY little onto the mix. This is just enough to hold it together and allows you to take a handful and compress it. It should hold the shape of your fist like wet sand would. DO NOT get it too wet.
Press it into moulds quickly and if making ball shapes press two moulds together to form the ball. For the spherical moulds, take one side off to allow the surface to dry slightly. With tray moulds, turn out gently when the top surface has dried a little. They are fragile at this point so handle very gently.
Leave in a warm, dry place to harden up. Resist the temptation to handle them.
Use cellophane bags to package when they are hard or put small ones into a decorated jar as a gift idea. Wash the moulds thoroughly after use.