Saturday, December 12, 2015

Weekend Wonderings: Using corn starch in bath bombs?

In this post, Back to Basics: Bath bombs, Annie asks: I found your link when I was enquiring on Google as to why cornstarch is used. I really couldn't find a valid reason and didn't want to waste time and ingredients. I always go to you - my first place to enquire on anything technical as well. It's coming up Christmas time and, because I make soaps and cosmetics, my friends presented me with a challenge for bath bombs, of all things, so I'm lying in bed researching. 

I've never found a good reason for including corn starch, so I don't use it. Bath bombs are a chemical reaction between an acid - citric acid - and a base - baking soda. Add water and they fizz like crazy! I use an oil to bind it all together, and the fragrance and colour make the bath bomb fun and fragrant. Corn starch doesn't add to the reaction and doesn't seem to add anything to the hardness or cohesion of the bath bombs I make, so I don't bother with it.

But this is just my opinion, and I want to know what you have to say! If you do use corn starch in your bath bombs, why? How much? How do yours compare to those without? Give us some of your thoughts on this topic!


Anonymous said...

I have experimented with adding cornstarch in a bath bomb didn't add anything to it. I do add some cream of tartar I find this does help with making it harder.
Karen S

Elisabeth said...

Some people experience that cornstarch makes the bath water feel silkier, though OTOH you need to clean it out of the bath afterwards. (Not having a bathtub, I'm making footbath bombs.) Have used cornstarch occasionally, if the mixture has turned out too moist,but wouldn't use it as more than a filler.

Kim said...

Hii Susan, glad to see you back on the blog!
I've always made my bath bombs with food coloring, the little plastic jars from wilton (not advertising). Its not something I thought about before but I assume they have water of some kind in them. What does that mean for preservatives?
Also, because I'd like to make strong colored imbeds I would like to use these types of colors but they are not water solluble and I don't really find a floating color layer very attractive in the tub. Do you have any advise on this?


Marg said...

Cornstarch is used because corn starch baths are helpful in soothing itchy skin. It also makes the bombs float a little more, and slows down the time it takes to for the bomb to dissolve.

Brandi Yates said...

You wanted us to comment on how they turned out so I wanted to say that my bath bombs always fall apart. Should I add more oil? I let them dry out for two days. They crumble easily. I would also like to know how to make the perfectly round ball bath bombs :)

Christine Russell said...

I use cornstarch and Epsom salts. Cornstarch should help with skin irritation or sunburn. But this makes me think that it could be used only in some, same with Epsom, and marketed accordingly.

Sarah said...

I really want to try bath bombs, but I've allowed myself to become overwhelmed with coming up with a perfect formula in advance. I'd like to give them as gifts, but I'm worried about shelf life. I've read that using water will help them get and stay very hard, but presumably would also limit the shelf life? Using only oils would improve the shelf life but may make them crumbly. Is that accurate?

Anonymous said...

For "perfectly round" bath bombs, I like fillable acrylic ornaments. Right now I have a humougous one, 2.36" in diameter. I'm going to be picking up a few smaller ornaments.

I bought the book, Make it Fizz, and nowhere in any of the recipes is water mentioned as an ingredient but something to stay away from to prevent premature fizzing :)

In the recipe I used, butters are part of what is used to help form the BB, with a handy spray bottle of witch hazel to act as a wetting agent. hope that helps

La Prairie Lady said...

Hello everyone

Too much oil makes them crumbly bath bomb, I use turkey red oil, it dissolves in water or any oil with polysorbate 80. I hate to see oil floating on the water. Corn starch for irritation, you can use colloidal oatmeal.

Leanne R said...

Hi all,

I don't use corn starch in my bath bombs. I don't add oil or butter. While I love the skin-friendly addition they bring, I don't like cleaning the tub right after enjoying a soak. I tried turkey red oil (which is water soluble) once, but I don't like the smell and find it hard to mask.

For every 2 cups of baking soda / 1 cup of citric acid, I whisk in 2 tbsp. of clay (white, green, pink, multani mitti....whatever color I'm going for), and sometimes I add a tbsp. or two of goat or coconut milk powder (for moisture/soothing properties). The clay really helps to harden the bombs.

In a separate container, I mix 1 cup of epsom salts with whatever fragrance (body safe only) or essential oils I'm using. Generally, I add about 2 tsp. of fragrant/essential oil per cup of salt. I shake it all together, then whisk quickly into my baking soda mixture. After completely blending it in, I then spritz with alcohol-free witch hazel, whisking very frequently, after every few spritzes. You don't need much! As soon as it will hold it's shape when pressed very firmly into the mold, do not spritz anymore. You can always add a bit more if the mixture dries some while you're molding. There is a bit of trial and error involved. Too dry and they fall apart (and become bath salts in a jar :)). Too wet and they morph into damp blobs. Try a few 1/2 recipes to get the hang of it. I live in Alberta where our humidity is generally very low, so I've not had to worry about them absorbing moisture from the air. Don't worry if you don't like the smell of witch hazel. It completely disappears once the bombs are dry.

Because I'm too lazy to make full "round bombs" (they tend to fall apart on me and it takes me at least twice as long), I make "half bombs", using one side of a round mold. My trick is to spritz the inside of the mold very lightly with cyclomethicone and wipe it around with a Kleenex. I use the small spray bottle that comes in those "travel bottle" packages at the dollar store. I repeat this "spritz" for each bomb I make. Cyclomethicone does not react with any of the ingredients, and it evaporates very quickly. Your bombs will release easily with a slight tap (I plunk mine on a cookie sheet with wax paper). I pack the half-mold as hard as I can with my hands (not too hard or you'll crack the mold), pressing down very firmly at the edges. Then I put a bit more loose mixture on top, flip the mold upside down, and twist it against the bottom of the stainless steel bowl I'm mixing in. I go for that "plastic on metal" sound. Then, I dust off any stray bits, and tap it out onto my sheet. A batch this size takes me less than 30 minutes from start to finish. I let them dry "face down" overnight, then flip them the next day to let the flat side dry.

I've had people tell me that they prefer the 1/2 bombs, particularly if they have smaller tubs. If they like full bombs, they just use two halves. The amounts above yield about 16 half bombs for me. My molds are 60 mm (about 2.5 inches) across.

Happy crafting!

Marjo said...

I dont make bathbombs but i can reason that if one uses oils
To put the acid and soda together
A bit of hydrophilic starch would be nice inclusion to
Let that oil bloom in the bath

I have no
Clue about non hydrophilic starches though

Brandi Yates said...

Thank you so much for so many detailed recipes!

Sharon BoydChapman said...

I make a few different types of bath bombs. My most popular one includes cornstarch as well as arrowroot and kaolin clay, and several other ingredients. I like the feeling it leaves. I think it helps soften and condition the water.

I wanted to add that I've noticed if I add either a polysorbate or SLSA to the formula then I don't have to clean my bathtub right away. It helps disburse the oils and butters, along with most colors, and sends them down the drain. If anything a quick swipe with a towel helps take most of the oils off the surface if there is too much left behind. I saw that was one of the questions that came up.