My bath bombs which are made with this recipe.....are rather soft..even after several days. Is there anything I can add to make them harder?? Ingredients 1 1/2 cups bicarbonate of soda (baking soda) 1/2 cup citric acid, powder 2 teaspoons sweet almond oil essential oils (or fragrance) food coloring 1First you need to make the base mix, to do this sift together the bicarb soda& citric acid in a large dry bowl. 2Transfer 1/2 cup AT A TIME to another dry bowl, to this add any dried flowers, glitter etc. 3Set aside. 4In a small bowl mix together 1/2 teaspoon AT A TIME of almond oil, 6- 8 drops of your chosen essential oil& 6 drops of food colouring. 5Pour the oil mixture into the 1/2 cup of base mix& mix QUICKLY before it starts to fizz! 6Combine with your fingertips until all colour is evenly distributed. 7Wipe a little sweet almond oil inside your moulds. 8Fill the moulds with the mixture, packing it in firmly. 9Repeat this process with 1/2 a cup at a time, using different fragrance/colour blends if you wish. 10Leave the bath bombs to set for 24- 36 hours. 11When set lightly tap the mould & ease out gently.