Bath bomb ingredients
Baking soda is one of the two key ingredients in a bath bomb – it's the reaction between the baking soda and the citric acid that makes the fizz. It's also one of the easiest ingredients to find, because we use it all the time in cooking. People often use it for cleaning, too.
Don't confuse baking soda with baking powder – baking soda is pure sodium bicarbonate, and that's what you want. Baking powder has all kinds of other stuff in – flour and salt and stuff – so that's not what you want.
You can get baking soda in most supermarkets, in the baking section. You can also buy it cheap in larger quantities on eBay or Amazon.
Citric acid is the other half of the dynamic duo of ingredients that creates the fizz in a bath bomb. The name sounds scary, but citric acid is actually totally natural and safe. It's just the stuff that makes lemons sharp! It's sometimes called 'sour salt'.
It's used as a preservative in jam and jelly making, also for water softening and cleaning. So, one place you can get citric acid is in the canning section of your local supermarket. You can also try a large drug store or pharmacy (ask at the prescription counter – sometimes they don't keep it on the shelves), or your local health food store. Failing that, you can get it online in bulk quantities at places like Bulk Foods.
Baking soda and citric acid are dry ingredients, they come as powders. So to make them into bath bombs, you need some moisture to get them to stick together! For this you can use water – but a lot of people prefer to use witch hazel, as it tends to be less likely to set off the fizzing early.
You can get witch hazel in pretty much any health food store, and most supermarkets. If you get it in a spritz bottle, it makes it easier to add to your mixture.
Bath bombs would be pretty boring without fragrance.
You have two main options for bath bomb fragrance. You can use essential oils, which have the advantage of having aromatherapy properties.
Alternatively, you can use fragrance oils. That gives you a wider range of options, as you can get fragrance oils in all kinds of incredible flavors, from delicious food-like scents to perfume-like blends of fruit and floral. Make sure you get skin-safe fragrance oils, not the kind made for burners.
See my resources page for some suppliers of essential and fragrance oils.
It's best not to use food coloring for bath bombs, as it may stain your tub. Instead, go for skin safe soap colorant. Micas are good. Also, LabColor make some specialist bath bomb colors called La Bomb Color.
See my resources page for some suppliers of bath bomb colorants.
Herbs and spices
Essential oils are great, but if you want to really get creative, you can go one step further back and add actual herbs and spices to your bath bombs. Herbs have all kinds of beneficial properties besides their smell. The Handcrafter's Companion has some great ideas for using these kind of ingredients in your bath products.
It's often nice to include a dash of some nourishing natural oil in your bath bombs, to make the skin feel soft and silky. Any nut, seed or vegetable oil will do, and you can have fun trying out different kinds. Be aware, though, that most will deteriorate quickly, so if you plan to sell your bath bombs, you'll need some kind of preservative or anti-oxidant to stabilize them. Jojoba oil is one oil which lasts a little longer.
Bath salts have all kinds of great benefits (visit my homemade bath salts site for more information), and you can add them to bath bombs, too – 1 part salt to 1 part citric acid and 2 parts baking soda is about right.
Any kind of salt will do, but for maximum health benefit I recommend Epsom salts or Dead Sea salts.
Here's a cute tip – if you add the color to the salts, and then add the salts to the mixture, you'll end up with a nice speckled effect, as the color will seep into the salts thoroughly, then disperse into the rest of the mixing, leaving you with darker specks of salt in a paler mix.
Kaolin clay or Bentonite clay
A little clay will make your bath bombs harder and less likely to crumble. Use about a tsp per 1 cup citric acid and 2 cups baking soda
Cornstarch or oatmeal
Cornstarch and oatmeal are nice skin softeners. If you use oatmeal, make sure you grind it up into a fine powder. One warning – avoid using cornstarch in your bath bombs if you have a yeast infection, as it can make it worse.
Sodium Laureth Sulfate and Sodium Lauryl Sulfoacetate
Sodium Laureth Sulfate is a foaming agent used in lots of commercial bath and hair products – basically anytime they want a product to lather. It's often used in bath bombs to create bubbles.
However, you shouldn't include sodium laureth sulfate in any recipe for sensitive skin, as it's known to be irritating. In fact, a lot of people prefer to avoid it altogether, so if you're looking to make all-natural or gentle bath products, it's best avoided. Check out the Natural Health Information Center for information on the possible dangers of sodium laurel sulfate.
A better option is Sodium Lauryl Sulfoacetate, which is a gentler and more natural foaming agent. To do a quick compare and contrast, Sodium Laureth Sulfate is made from sulfuric acid, monododecyl ester, and sodium salt – yuck. Sodium Lauryl Sulfoacetate, however, is made from coconut and palm oils, and is skin safe – I'm told it's safe even for children, but as always, I'm not a chemist, so please do your own research or ask an expert to be sure.
You can buy Sodium Lauryl Sulfoacetate from various specialist suppliers such as bathbodysupply.com.
See my bubbling bath bombs recipe for how to use it in your bath bombs.
A lot of people use a little borax to help the bombs hold together. I personally don't like it because it's toxic, and as much as people insist it's safe in small quantities, I just figure why take the risk?