S-7 Development Notes #5 | From a Test Batch to the Salon Floor

← Entry #4: S-7 Development Notes #4 | The Salon Intuition Science Couldn’t Explain

The last chapter already had its sequel waiting inside it. Two things had come into focus — the lather, and the way hair felt after washing. The formula was starting to become an actual shape, not just an experiment.

Then, in late July 2025, I made a 1000g batch for the first time.

A 200g beaker became 1000g. Reduce it to a number, and that’s all it is. But for me, it felt like crossing a real line. 200g is an “experiment” amount — I try it on my own hair, and if it doesn’t work, I wash it down the drain and move on. 1000g is a different kind of amount. It’s enough to sit on a shampoo station in a working salon. From this version on, S-7 stopped being a liquid that only touched my own hair, and became one that might touch a client’s.

What turning it back down taught me

Actually, in the batch right before this one, I’d lowered the ratio of an ingredient that had been carrying the lather’s body. Everything was being pulled toward a milder, everyday-use direction, and that ingredient was part of the adjustment.

My hands caught it immediately.

The lather wasn’t thick enough anymore.

It still cleaned fine. Nothing was technically wrong. But it wasn’t the lather my hands remembered. If you’ve been reading this diary, you can probably already guess where this is going — yes, another one of those hand-feel stories. Ha.

So for the 1000g batch, I put the ratio back. But “putting it back” wasn’t a step backward. It was only by lowering it first that I understood exactly what that ingredient had been doing for the lather’s texture. If I hadn’t lowered it, I don’t think I’d ever have gotten that certainty.

“Eighty percent there”

I brought the finished 1000g batch into the salon and started using it.

I still have the note I wrote at the time:

“Feeling pretty good! The lather’s got its bounce back. Eighty percent of the way there for using on clients — though if the scalp’s really dirty, you need a lot more product. But it feels gentle on the hands.”

from my notes at the time

Eighty percent. That was the honest read back then. Not perfect. On hair with a lot of oil or styling product built up, the lather would disappear fast and you’d need more of it — a clear weak point that came with leaning mild.

Even so, I put it to work. I could have kept it in the lab a little longer — which, let’s be honest, was just a corner of the same salon — until it was flawless. But there’s so much you only find out by using something every single day at work. And the feel while washing isn’t the whole story anyway. Rinse-out, how conditioner sits on top of it, how easy it is to dry, what the hair feels like once it’s dry — lay all of that out, and it’s not eighty percent at all. More like forty. Ha, I’m laughing writing this, but there really was a sense of solid progress in the feel of it.

Turns out, it’s gentle on hands too

And here’s the real step forward — the thing I’d been hoping for the most.

The last line of that note: “But it feels gentle on the hands.” Honestly — and I feel a little sheepish admitting this — that mattered to me because, in a way, this shampoo is for me too.

A hairdresser washes hair many times a day. A client might shampoo once a day; we do it for person after person, every single day. Rough, cracked hands are practically an occupational hazard in this job — back when I was an assistant, I watched more than a few people quit because their hands gave out.

So the idea that I could use it every day and my hands wouldn’t scream back mattered to me as much as the lather’s texture. Honestly, if anything, it mattered more.

Think about it: a shampoo puts a hairdresser’s hands and a client’s scalp in the exact same position. The same liquid touches the washing hand and the washed scalp for the same stretch of time. The point of leaning mild wasn’t something I first understood from a formulation notebook — my own hands taught it to me before anything else did.

That “gentle on the hands” feeling from this batch went on to become something like the backbone of S-7.

Not asking one bottle to do everything

So what about the weak point — the lather not being quite strong enough?

The note from back then kept going: “If I split duty with something stronger, this might actually work for the salon floor.”

Don’t ask one product to do everything. On a day when the scalp really needs it, reach for something stronger. For most everyday washes, this milder one is enough. If anything, because it’s made for daily use, it should lean gentle rather than strong.

The “7” in S-7 is the seven days of the week. That idea had already been sitting in my head since back when all I had was a book and no name for any of this.

The test batch made it to the salon floor

A 200g experiment turned into 1000g, and made it onto the salon floor.

From here, it’s a long trip of adding, removing, and adding again. Ingredients I put in with good intentions ended up coming back out; some that disappeared once found their way back in. Next time, I want to write about that — the ingredients I tried, and chose not to use.

Deciding to leave something out is, I think, harder than deciding to add it. Against an industry that keeps piling more and more into every bottle, I went in ready to go head-to-head with simplicity and gentleness instead.

🇯🇵 日本語版（オリジナル）→ https://masashitt.com/2026/08/10/the-first-1000g-batch/

I’ll share S-7’s launch news first with the people who’ve joined the launch list.