Have you ever watched someone drop their shampoo bar in a glass of water, waiting for it to float or sink-and then make a bold claim about its quality based on that? It’s a trend that’s making the rounds online, but as someone who’s spent over twenty years behind the salon chair, I'm here to pull back the curtain on this so-called “soak and float” test. Let's dive into what this test really means, and why your hair deserves better than a simple sink-or-float experiment.
The soak and float test was originally designed to help people determine hair porosity-how much water your strands can soak up. Slowly, the test found its way into the world of shampoo bars. But here’s the secret: what happens to your solid shampoo in a glass of water doesn’t actually reveal much about its performance in the shower or its effect on your hair.
What Does the Soak and Float Test Actually Tell You?
If a shampoo bar floats, some folks will say it’s light, gentle, or “airier” and therefore better for your hair. If it sinks, others argue it’s denser and richer, packed with potent ingredients. The truth is far more nuanced.
- Floating bars are simply more aerated, sometimes whipped to include little air pockets. They might be lighter but that’s more about how they were made than what's inside.
- Sinking bars are tightly packed and dense. This doesn’t automatically mean they cleanse or condition your hair better-it just means they contain less air or heavier ingredients.
Bottom line: Sink or float tests reveal density, not haircare magic. It’s science, not sorcery.
What Really Matters: Water, Wear, and Your Shampoo Bar
1. Bar Longevity and Dissolution
When you soak a shampoo bar, even briefly, you kick off a process almost no influencer talks about. Water begins working through micro-cracks and pores, softening the surfactants and melting away that precious top layer. If your bar is prone to soaking up water, it will dissolve rapidly-meaning you’ll go through it much faster than you should. Most high-quality bars, like those inspired by traditional rituals, are formulated for gentle hydration and efficient lather, but still depend on proper care.
2. Ingredient Loss
Specialty bars, especially those containing ingredients like Longsheng rice water, are packed with hair-loving proteins and nutrients. Leave your bar soaking and you risk leaching out these actives before even getting them onto your scalp. The result? Fainter scent, weaker efficacy, and a disappointing experience, no matter how luxurious the bar was on day one.
3. Hygiene and Microbial Growth
This is a detail most skip, but waterlogged bars invite bacteria and mold. If you want your product to stay safe and fresh for every wash, make sure it dries fully between uses. This not only keeps things hygienic but ensures every lather is as clean as the last.
How to Get the Best Results From Your Shampoo Bar
The secret isn’t in the float test-it’s in your daily habits! Here’s how to make your shampoo and conditioner bars go the distance:
- Always let bars dry completely between uses. Store them in a well-ventilated holder, like a bamboo tray, rather than a puddle.
- Avoid pre-soaking. Just wet the bar briefly before building up a lather in your hands or on your hair.
- If your bar gets mushy, allow it to dry out thoroughly. Trim off any soft outer layer if needed, and rotate use with a second bar if you wish.
Proper storage and mindful care make a much bigger difference than whether your bar did a cannonball or floated like a lily pad in a cup of water.
Buried Myths and Professional Wisdom
The soak and float method might make for a fun Instagram story, but it’s not a sign of quality, purity, or potency. Exceptional bars are made with a balance of the right surfactants, emollients, proteins, and natural oils-not with air or water alone.
As a stylist, what I care about is how your hair looks and feels after every wash. Choose products made with intention, and treat them with a little TLC. You’ll be rewarded with healthy, soft, and vibrant hair-no glass of water needed.
In Summary: Know Your Bar, Ignore the Hype
- The float test only measures density-not quality or performance.
- Your bar’s lifespan and hygiene depend on how you use and store it, not on water tricks.
- For brands using time-honored traditions and real science, what matters most is ingredient integrity, pH balance, and your habits as a consumer.
If you ever have doubts, remember: the best “test” is always the real-life results in the mirror and the effortless feeling of clean, nourished hair. Not what sinks or floats in a cup on your bathroom counter.
Have questions about optimizing your routine or making the switch to a solid shampoo? I’m always here to share-and maybe geek out a bit-about real hair science and pro tips. Happy washing!