A friend once called me from a building I had just left. Were you just in the elevator? I could smell your perfume. I had not been in that elevator for ten minutes.
I think about that call more than it deserves. I was already gone. The scent was still doing something, to someone, on my behalf, and I would never know how it landed. That is sillage, and it turns out to be the thing I care most about in everything I make.
Everything is little things
Start with the boring truth about perfume: it is a bunch of small scents combined until they make one thing. Music is the same. One song is a bunch of small sounds, and if you go a layer down each sound is a bunch of frequencies, and a layer under that each frequency is a bunch of amplitudes, and under that it is just a lot of very small things. You can keep going. It does not stop being true.
A function in code is the same idea with a different name. Everything I have ever built is layers of something smaller.
This is also, honestly, how I solve problems. If a problem is big, I make a smaller one out of it. If that one is still too big, smaller again, until it is so small that fixing it is obvious, and then I climb back up. It is how I learned to program. It is how I learned what a function even was. It is a crucial part of how I live, and I did not notice until recently that it is also how a perfumer works, and how a producer layers a track, and how nature does almost everything. I keep finding biomimicry in places I did not put it.
Break it down until it is easy. Then build it back up. Perfume, music, code.
What I wear, and why it is mine
I wear what I feel like wearing. What I like will not be what you like, and I think that is one of the most interesting facts about people. We all arrive on earth as more or less nothing, the same nothing, and then we grow into something that is only ours. It shows up in handwriting, in how you walk, in how you write code, in what music you can stand. We are all essentially the same and all essentially unique at the same time, and perfume is the most intimate version of that I know.
So I am chaotic about it, and the people who know me know this. Some days I want something simple and clean. Some days flowery. Some days unisex, some days something that reads as masculine. I have a decent array now. My sister taught me most of what I know, and I started where a lot of people start, with Carolina Herrera, and moved through Libre and a lot of others from there. Kayali is a house I follow closely. Their juicy apple layered with their pistachio is one of the best combinations I have found, and I am going to keep claiming I invented it until someone proves otherwise.
I almost never wear one scent. I put on two and find out what they make together, and I have discovered things I love that way that neither bottle would have given me alone. Some days I just want to be vanilla, so I wear vanilla in three different shades of vanilla. Why not. Layering again. It is always layering.
I do not spend much on things. If I am going to slip, it will be on perfume or on technology, and I am at peace with that. Perfume is intimate in a way most purchases are not. It is the closest thing to you all day. There are tricks, too: a little Vaseline on the skin before you spray and it holds for hours longer. But mostly the answer is to buy the one that lasts, which brings me to the trade-off, and I will get there.
Reading other people's trails
I can walk into a room and know my sister was in it. Everyone has their own scent, and sometimes I walk into a place and think, this reminds me of someone, and then, this reminds me of a time. Smell files things by person and by period without asking you.
Can I read a stranger from their sillage? A little. There is a particular masculine scent I can pick out on men that tells me something about who they are hoping to run into. Mostly what it tells me is whether they know anything about perfume, because if I can name what someone is wearing we can have a conversation about it. That is a good one, I will say, or, you should try it with this. People are sometimes surprised that I know. Other people think it is common knowledge. Both reactions tell me something.
Interfaces have a smell
When I was taking my fundamentals of interaction class, I kept reaching for scent to explain things to myself, and I think it holds up.
Walk into a room and you can smell that it is clean before you have looked at anything. Walk into an Abercrombie and you are hit with the store's own perfume, sprayed on purpose, and Victoria's Secret does the same. The brand has an essence it is trying to give off, and it gets to you before a single word does.
Interfaces work exactly like that. You can tell something is clean. You can tell something is smooth, or pastel, or sharp, or bubbly, before you have read a label or pressed a button. You eat with your eyes, people say, and it is true of a website. But you also eat with your nose: if the food smells off you do not want it, and biology put that reflex in front of your thinking on purpose, so that spoiled things get rejected before you have to reason about them. An interface gives off a smell in the first half second, and whatever it is, the user has already decided something.
There is a famous experiment where people are shown two shapes, one spiky and one round, and asked which is called Kiki and which is called Bouba. Almost everyone says the spiky one is Kiki. Nobody taught them that. We feel shapes the way we smell rooms, and design is just a way of choosing what people feel before they think.
Designed to fade
Here is the thing perfumers know that software people mostly do not: you design in time. A scent has top notes that are bright and gone within the hour, heart notes that hold for the afternoon, and base notes that are still on your coat the next morning. The entire craft is deciding what fades when. Nothing in a good perfume is meant to last forever, and that is the design, not a limitation of it.
I have been asked why I keep making things that go away, when the whole industry is built on things that pile up. Accumulation is fine. It is also a kind of hoarding. People want to keep every image and every message, and it all takes space, and space costs money, and eventually it costs convenience too.
Think about a Polaroid. You take one picture. You hand it to a friend, they look, they hand it back. You show the next person, and the next, seven people if you like. At the end you still have one photograph and seven people have seen it, and it cost you nothing to show them. Digital broke that. Now, to show seven friends the same picture, I send it seven times and there are seven copies of it living on seven phones, and mine, and the act of showing someone something has quietly started costing storage, which is to say money. Ember exists because I wanted the Polaroid back. Show it to the people you chose, let them look, let it go.
A perfumer would understand that immediately. Of course it fades. What did you think it was for?
The one time someone tried to put actual smell into software, as far as I found, it did not go well. A game studio, I could not tell you which one now, worked on a device that would release scent to match what was on screen: flowers when you walked through a field, pizza when you saw pizza. It ran on a few chemicals mixed in a cartridge, and over time the cartridge just started to smell bad. Every combination decayed toward the same off smell. There is probably a lesson in there about mixing things that were never meant to sit together in one box, but I mostly find it funny. Somebody built a fart machine by accident while chasing the flower field.
The trade-off is the same one
What I dislike about how perfume is sold is the price, and the honest answer to the price is that you can usually get the same scent for a lot less, and it will not last as long. That is the trade. Longevity or cost. Pick.
Which is exactly the shape of every trade I make at work. Overfit or underfit. Bias or variance. Storage or the ability to look at the photo forever. Privacy or convenience. There is no version of a system where you get all of it, and a lot of what I would call taste, in perfume or in engineering, is just knowing which side you are willing to lose on, and being honest that you chose it.
So, what would a perfumer build?
Something layered from small parts that each do one thing, the way a scent is built from notes and a song from sounds. Something with a shape in time: a bright opening that gets out of the way, a middle that holds, and a base you only notice once you have stopped looking. Something that leaves a trail you never see yourself, in what other people say about it after they close it. And something that fades on purpose, because a thing designed to last forever was never really designed at all.
I was gone from that elevator for ten minutes. The best thing I could hope for anything I make is that it keeps working on someone after I have left the room.