Everything you need to know before making the blackest bath bombs possible
Black bath bombs look incredible in the water and always make an impact, but they can also bring the most questions…
How much colour is too much? Why do some tubs stain and others do not? Does blooming help? And what if the foam comes out grey?
The good news is that black bath bombs are completely safe when you understand how to make them. Here is everything Soak makers have learned, based on loads of real tests and shared experiences.
Does blooming actually help? 💦
Yes, blooming makes a huge difference with black dye.
When you dissolve your colour fully in water before adding it to the mix, it releases the pigment properly, prevents speckling and gives a much richer finish.
Makers who bloom their black dye report smoother bombs, deeper colour and far fewer issues with residue sticking to the bath.
How to create the blackest black 🖤
For a true jet black, most makers use between 3 g and 4 g of water-soluble black dye per kilogram. Many makers avoid using black mica for full bombs because mica can cling to uneven or textured tub surfaces more than dyes. But, if you do use mica, keep usage low and include polysorbate 80 to help it disperse.
Here’s what our Soakies have previously reported:
• 1.7 g per 1 kg gives a grey black
• 3 g per 1 kg gives a strong black
• 4 g per 1 kg gives jet black
Blooming helps each gram go further, and using enough water during the blooming stage gives a stronger colour release.
The best way to test your black 🛁
Always test your bath bombs in a half-full bath, because testing in shallow water concentrates the colour and can make it appear as though it is staining.
When makers retested in a deeper bath, even the darkest black did not stain at all and rinsed away easily.C
Clean vs dirty bathtubs ⚖️
Colour sticks to dirt, not the bath itself. Any leftover oils, soap scum, deodorant or moisturiser can attract black dye and make it look like staining.
This is not permanent and will not happen in a clean tub, which is why cleaning before testing (or even adding a note of this to your packaging) is so important.
How to clean a tub if this does happen 🧼
If you do see marks, they are temporary and come off quickly. Washing up liquid, a magic eraser, Flash Bicarb spray or a damp cloth will remove every trace.
Makers found that even heavy residue wiped away without scrubbing once the tub was rinsed properly.
Key tips for safe black bath bombs 💪🏼
• Bloom your colour for even black
• Use 3 g to 4 g per kilogram for deep results
• Test in a half-full bath, not shallow water
• Avoid black mica unless you know your recipe well
• Remind customers to use your product in a clean tub
• Rinse after use for best results
