Bathtub Science

In the summertime when the weather is hot, the humidity is high and the PSI is through the roof, there’s nothing better than some refreshing bathtime fun for reviving the tiny limp ragamuffins!

We do like to treat the kids to a soak in the bathtub every so often. All three of them are still at an age where they are completely comfortable with ofuro-style bathing, that is, a communal family bath time. We encourage this as sibling-bonding is of high importance to us…and of course it is fun to relax together.

The Barn Owl and I have found several ways to make bathtime a multisensory learning experience…and right now we like to switch things up a notch using the Power of Science!


Picture Credit: Metanorn

1.Colours, Scents and Chemical reactions using Bath Bombs

If you aren’t familiar with Bath Bombs, here’s a little video that shows you what happens:

The Bath Bombs that we use are from LUSH. These generate a whole lot of fizz and turns the water a brilliant colour. They also smell really good and their natural, nourishing ingredients are great for the skin. The scent usually lasts for hours afterwards – so we get three, clean, lovely smelling children who are completely relaxed and ready for bed afterwards!

The kids are usually mesmerised by the effervescent bath bomb when it first goes in, and both Thumper and Little E love watching the colours swirl into the water.

Mummy Pro Tip: For a really great fizz, choose a Bath Bomb that is less oily and make sure that the water is really warm before you put it in – if you’re worried about making the bath water too hot for your sensitive kiddies, dunk the Bath Bomb into a clear container of hot water for your kids to enjoy, then add it to the main bath once it reaches the desired temperature

Each Bath Bomb gives a completely different bath time experience – some of them have sparkles, some have tiny heart-shaped confetti (which the kids like to line up in little rows on the side of the bath, competing with each other to see who can make the longest line), some even contain a secret message. I like the multicoloured ones for a live demonstration of colour blending in the bath to Thumper and Little E, but the real fun is when we start talking about the ingredients of each bath bomb. J and I now play a game where we try to identify the ingredients of each bomb based on the smell, which usually leads to a discussion on the source and origins of each ingredient – but of course, the first time the kids were introduced to the Bath Bomb, they begged me to explain to them how it worked.

Warning: Science!

Basically, the main ingredient in each Bath Bomb is Sodium bicarbonate, a weak alkali, as well as a weak acid (usually citric acid). When it is left dry, nothing happens, but when the dry sodium bicarbonate and citric acid in the Bath Bomb are activated with water, the acid-base reaction leads to a release of carbon dioxide bubbles – all the fizz that you can see – and sodium citrate!

Buyer’s note: LUSH does have a storefront in Singapore and you can buy from their online store for delivery within Singapore too. If you happening travelling to the UK, USA or Australia, LUSH is waaaaay cheaper out there, so stock up if you can!

2.Electricity and circuits using the Sud-Z-Buddy

Okay, when Mummytoon contacted me to try out the Sud-Z-Buddy, I was super excited about it because it just sounded SO COOL. I mean, this is a toy encased in a clear glycerine soap – and it lights up only when in contact with water!

The soap itself is a mild, fragrance-free soap that contains no parabens or sulphates, so it is suitable for sensitive skin. The toy is also phthalate and lead-free, and the battery voltage it contains is minimal (basically, the same as wearing a watch in the shower), so there is no risk of electrical shock.

Imagine the look on J and Little E’s faces, when I immersed the soap in water and it began to glow and pulse in a myriad of colours! It was like having a disco in the bathroom! PARTY! PARTY!

Mummy Pro Tip: You’re not supposed to use the soap in the dark for obvious safety reasons, but if you’re planning to be in attendance during bathtime anyway, why not? Put on some tunes, turn off the lights and PARTY!


Party on with the Partysaurus Rex! Picture Credit: Pixar

Thumper was so excited about the Sud-Z-Buddy, he just kept splashing his hands about, trying to grab it, and laughing as it slipped away from his grasp.

Once the soap is completely used up, you’ll still be left with a super-cute bath toy! The soap itself makes a nice lather, and it doesn’t get mushy, so it lasts a pretty long time. We’ve been using the soaps for about 3 months and we still haven’t uncovered the toy completely.

Warning: Science!

When examining the bottom of the Sud-Z-Buddy, there are two tiny metal bumps spaced about an inch or so apart. These are electrodes, and washing the soap in water completes the current pathway between the electrodes, closing the electrical circuit so that the toy lights up.

Buyer’s note: You can get Clancy Clownfish and Ophelia Octopus from, which also carries other kid friendly bath things as well as gentle products for eczema prone skin. I like their California Baby range as well as the Burt’s Bees range especially.

3.Submarines and buoyancy using diving pool toys


Picture Credit: Swimways

Well, there’s no reason why a pool toy can’t also be used in the bath, especially, if they are awesome diving toys like the Submergency and Submergibles by Swimways.

These are basically little brightly coloured plastic balls which you twist to adjust their buoyancy. They can sink right to the bottom, float on the surface or even suspend themselves in between, just like a submarine! As you may imagine, the kids were fascinated by how it works and we had many conversations about how submarines and ships work, and also about swim bladders of fish.

Warning: Science!

When a submarine floats, it is because the weight of the water that it displaces is equal to the weight of the submarine. To control it’s buoyancy, a submarine has ballast tanks that can be filled with water or air. When the ballast tanks are filled with water, the submarine becomes heavy and sinks. This is the same with the dive ball – when it is filled it with water, it sinks, but if it is filled with air, it floats. If it has some water and some air in it, it will sink below the surface but not all the way to the bottom!

Buyer’s Note: The Barn Owl spotted these swim toys at Toys R’ Us, which is where we got ours, but we have also seen them at various retailers that specialise in swimming things.

What are your favourite bathtime products? Share them with us in the comments!


29 thoughts on “Bathtub Science

  1. These are so cool! We don’t have a bathtub, so we can’t try out the bath bombs, but maybe I’ll get one if we go on a staycation (at a hotel with a bathtub of course). Think Noah would be thrilled to play with both items!

    • If you don’t have a bathtub, the Sud-Z-buddy is still pretty fun in the shower, and the dive balls are still fun toys for the pool – or even if you have a basin of water to splash!

  2. Such interesting and unusual toys! We don’t have a bathtub either, and I think these would be too large for the baby bath tub (which my kids still love?!). Maybe I can buy and keep them for staycations or holidays 😀

  3. Pingback: Friday Break: A Sud-Z-Buddy Surprise | Owls Well

  4. whenever we go for staycations or overseas holidays, we try to book a room with bathtub and then we will recycle the empty mineral water bottles after drinking as our boys’ water play equipment. they have a lot of fun scooping water, pretending the bottles are boats, and pouring water on one another with the humble bottles.

  5. My son is going ga ga over a small stretchy splash octopus lately. He would bring it everytime he takes a shower.

  6. My little angels simply love to play with bubbles. It never fails to bring big smile & laughter whether it is blowing bubbles or simply making more & more bubbles on their body using body wash. The most they love to have beard like Santa 🙂

  7. My kids favourite bath toys are their free style swimming on the floor, blowing lots and lots of bubbles using the shower gel and their water guns. Have to asked them to quickly shower and not spent so much time in the shower. No bathtub but have a bigger pail so that they would be able to soak these adorable and glowing soap on it. I can’t imagine how thrilled, excited and gaga over this bath bomb.

  8. My kids’ favourite bath toys are empty containers of various sizes. I sometimes let them have free reign of some hotel shampoos and soaps. They love to pour, mix and fill, and create ‘potions’!

  9. Wow!! This is so cool!! Now I wish my home got a bath tub … I can imagine the children having fun with the bath bombs and probably stay longer for their bath.. 🙂 But this seems nice to bring along to a hotel (with bath tub) . The diving toys looks fun too! Can bring along to the pool!

  10. These science facts behind the bath-time fun are sooo way cool! I never knew the bath bombs are so fascinating, shall buy one for the kids to try in our tub.

    • Yes! If you’re into ofuro-style bathing like we are, I’m sure your 2 kids will love the bath bombs – and they’ll be smelling sweet for hours. It’s also a great way to relax the littlest one before bedtime.

    • Yes, it’s definitely not an everyday thing – but as we bathe all three kids in it at the same time, we find that it is still quite water-saving!

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