Bath bomb woes

[nattiecakes.livejournal.com]

I'm fairly new to this community, so hello! :-) I've checked all the memories on the topic of bath bombs, and I'm still not sure what I'm doing wrong, so here goes...

I'm trying to make bath bombs similar to the Lush bath bombs in hardness.

All Lush bath bombs use as a base is...
baking soda
citric acid
fragrance and essential oils ONLY (i.e. no fixed unscented oils)
coloring

So, important to note is that they don't use: salts, fixed unscented oils, glycerine, or witch hazel. If they use water, they don't list it as an ingredient. I especially don't want to use fixed oils or glycerine anymore because those made really greasy bath bombs, and I'm trying not to use anything I don't absolutely have to use.

I have determined to get the level of scent I want, I really have to use roughly 3mL of fragrance oil per bomb, which is much higher than most recipes suggest (but most recipes I've tried have a REALLY weak fragrance). I shape the bomb using a big meatball scooper (1.75 in diameter). This makes it easy to not use any fixed oils, because that's about enough oil to adequately mix into the dry ingredients for a bomb that size. Also, for now all I have to work with are 3mL fragrance samples, so I can't really make more than one at a time with the intensity of fragrance I want them to have...

I have been using a 2:1 ratio of baking powder to citric acid. So, this is the recipe I've come up with for a single bath bomb so far:
1/4 cup baking soda
1/8 cup citric acid
3mL fragrance oil
tiny pinch of dry coloring

I am adding the citric acid last, after the water/witch hazel.

Now my big problem: I've tried several recipes online and tried several modifications and nothing seems to work to make them hard enough. I am having big water issues: I don't understand how much water I'm supposed to be using.

- Whenever a recipe specifies in teaspoons, it's always too much water and the stuff starts expanding like crazy and I end up with goop. I prefer to use a spritzer anyway.

- Whenever it just says "until it packs in your hand," I have a problem because it'll pack in your hand without any water whatsoever, and with very little oil, fragrance or otherwise.
BUT: when I make bombs with no water, they'll mold and everything, but if I pick them up the next day and squeeze even lightly they'll completely disentegrate into a sort of moist dust.
SO: I've tried adding just a spray or two of water, and while they're somewhat harder they're still pretty weak; if I drop them from even less than an inch, they shatter into some dust and multiple pieces. I guess they're more "brittle" than "hard" then. Lush and other commercial bath bombs are pretty sturdy, like if I dropped one one on the floor it would only break into two or three big pieces maybe.

- One recipe said to wet the baking powder until it is the consistency of wet sand for a sand castle. When I did so, it was even worse than the recipes that specify a certain amount of water; complete goop once I put the citric acid in.

Lush doesn't use witch hazel, but out of desparation I decided to try it. I don't get any better results. :-(


Does anyone have any advice for how much water/witch hazel I should be using for a little less than a half cup of dry ingredients and 3mL of oil? (Or just in general how much per x amount of dry ingredient? I'm considering ordering 1 oz each of some fragrances so I can make a bigger batch anyway; 1 oz would make 10 bombs in my case.) I want as hard a bath bomb as possible, because I'd like to give these as gifts. :-/ Thanks for any help.