You pick a scent, a gorgeous one that smells like Vanilla caramel ice-cream and the bath bomb turns out perfect! You high five everyone and give yourself a pat on the back for a job well done. A week later however your beautiful white bomb turns into... a weird brown spotty.. creation? It has happened to most of us who are learning at some point. Most of those delicious bakery scents contain vanillin, which over time discolours in your products to brown.
In a closed dark container to reduce exposure to light and air to slow down the process of oxidation. For most products, bottles with pumps or disc caps are a better choice than jars. When displaying keep them out of direct sunlight as much as possible.
like Vitamin E at 0.05% to your product to slow down oxidation.
A basic one is Titanium Dioxide. You only need a tiny amount and choose the right one for your product for oil or water-soluble before adding to the cool-down phase. Taking a small amount of the product out and mixing it well in a container before mixing it back into the whole batch will help you avoid clumps.
It might not work well with a lotion or other leave-on product, but a few extra drops of liquid colorant in a bubble bath or shower gel easily disguises the slight browning.
Did you know vanillin can also impact more than just the color of the product? Because it’s polar, it’s soluble in water. (Water is polar, oil is non-polar, and the rule is “like dissolves like”, so polar things usually mix well with water.) When including it in an anhydrous product, like lotion bars, whipped butters or paraffin candles, vanilla can show up as a light film on the surface or small droplets at the bottom of the container. If you’ve noticed this bloom and it bothers you, include a bit of a non-ionic solubilizer, like polysorbate 20 with the fragrance oil to make sure it stays emulsified.