Bath bombs are more effective when thoroughly mixed and compacted in the mold. If there are any clumps or pieces of ingredients in the mix, this is going to interfere with the compaction and the performance of the bath bombs once hardened. So, if you are asking the question: Should I Sift My Bath Bomb Mix? Then yes, you should absolutely sift your bath bomb mix.
This is not going to be a difficult step. You can go to any box store and pick up a sifter. But be careful with the quality. I have used some from a certain store where most things are $1 (HINT 🙂 and they will begin to come undone very quickly. This is not a good thing as pieces of the sifter, ie metal slivers, can fall into the bowl. So get a sturdy sifter. My recommendation is the:
Using 3 sets is always a good idea. It will give you the flexibility to use the smaller ones for other items like colorant and salts, and keeping the larger one just for the bath bomb dry mix.
At first glance, you might not think there are really any clumps in the sodium bicarbonate or the citric acid. But as you sift through the mix, you will uncover some little pieces. These are what need to be broken down into the bowl. Once you sift the mix and find any chunks, then just push them through the mesh strainer with your hands.
The reason for sifting is the exact same reason bakers sift their mix. It ensures everything is broken down into its’ smallest form, which ensures a better mix when being blended with the other ingredients. For bath bombs, it ensures when you press your wet mix into a mold, you don’t end up with white clumps of baking soda, which will mess up the color,. Plus, baking soda will not hold up very well in the compacting by itself. It need to be bound with the citric acid.
I personally never make a bath of bath bombs without sifting it first. It might take an extra 10 seconds, but with the amount of work you are about to put in to this project, it is well worth it. So, sift your bath bomb mix and you are on your way to a smoother and better performing bath bomb.