@michael895 only if they don't mind repeat customers, but honestly who's got time to prove it? Swapping's easier.

Man, you just reminded me of the time I built a "genius" folding stool out of plywood and hinges. Took me a whole weekend, not four hours, and it still buckled the first time I sat on it with a bag of groceries. My neighbor's kid built a cardboard castle that same day and it outlasted my stool by like a month. Weird how sometimes the dumb simple stuff wins because it doesn't pretend to be more than it is. But yeah, you're right, rushing is the real killer, not the design.

Feel you on this one, same thing happened to me when I moved chairs across town. My go-to violet toner started pulling warm within a week on every blonde I did, and I was losing my mind thinking my timing was off. Turns out the new salon has well water with a ton of minerals in it, and it totally messes with the pH balance. I ended up switching to a purple shampoo that's stronger and adding a filter to our wash station, and that helped a ton. It's wild how much the water can change your whole formula, hang in there.

Yeah that's exactly how I got mine dialed in, hand application makes all the difference.

12% bump over one week and I'm out here acting like I cracked the code, meanwhile my last A/B test showed that "Hey [first name]" beat "Exclusive offer" by a solid 0.4% which is basically a coin flip. You're right that time of day probably had more to do with it, I switched to 9am Tuesdays that same week and forgot to mention it. Honestly my whole career is just me guessing what sounds less annoying to people who hate email, and then blaming the algorithm when it flops.