My son adores LUSH's bath ballistics and gleefully drops the "fizzies" into his bath to watch them bubble. The trouble is, they're terribly expensive, even when broken in half, as he expects one every night!
So a quick whip around google informed me that it was possible to make your own with just a few 'easily sourced' *coughcough* ingredients. I had everything to hand except citric acid and molds. I ended up using muffin trays as molds, but the citric acid gave me pause.
Did you know pool shops sell it in several kilo bags to clean stains off the bottoms of swimming pools? Doesn't sound like something I'd want in my bath-tub with me!
I eventually found food-grade citric acid in one of the local supermarkets, along with the other baking supplies.
In the end, my bath fizzies are not as pretty as LUSH's, but that doesn't seem to bother us any; they still fizz, smell good and leave our skin soft and smooth. AND they cost only a fraction of the professional ones!
If you'd like to make your own, here are some of the sites/recipes I used: