of almond oil, a few drops of your desired food colouring (if you only have a couple of colours you can consider letting the kids mix the colours to make a third!) and a few drops of your chosen essential oil.  Mix them well so that they bond.  Now you're going to add your wet ingredients to your dry ones and mix them quickly so that the bicarb and citric acid don't fix too much.  You want to save some of that fizz for the bath! I had to help my kiddo with the mixing part to make sure that the small amount of wet ingredients were thoroughly combined with the dry ingredients so that the bath bombs set properly.  Otherwise you're going to end up with crumbly bath bombs that aren't solid. Once you've mixed it thoroughly, you're going to start filling your moulds.  The trick here is to compact them down into the mould with the back of a teaspoon as you go and when you think you've reached the top use your fingers to press the mixture down into the moulds even more.  You'll get quite a bit in each shaped hole. Tip: if they're not squished down properly, they'll come out in pieces rather than a solid shape. Depending on the weather and humidity in the air your bath bombs will take 24-48 hours to thoroughly dry.  To get them out, you just flip your ice-cube tray upside down and gently push each bath bomb out