The first blend most people make is three or four oils they happen to like, poured together in roughly equal amounts. It usually smells like three or four oils poured together. The thing that turns a pile of oils into something with a shape is knowing that aromatic materials evaporate at wildly different speeds, and building deliberately across that range. That is the whole idea behind top, heart and base.
What the three notes actually are
Nothing mystical. It is a description of how long a material stays in the air.
Top notes are the light, quick ones. They are what you smell in the first few minutes and they are largely gone within the hour. Citrus lives here almost entirely: sweet orange, lemon, mandarin, bergamot, pink grapefruit. The mints belong here too. So, awkwardly for the tidiness of the whole system, does elemi, which is a resin and by rights ought to be a base, but distils into something bright, lemony and peppery that arrives immediately and leaves early. Tops give a blend its opening and its brightness, and they cannot carry it alone.
Heart notes are the body. They arrive as the tops fade and hold for a few hours, and they are what people actually remember, because this is where the blend spends most of its life. The florals sit here, along with rose geranium, lavandin, ho wood, clary sage, ylang ylang and the softer herbs such as rosemary. Some of those straddle the line and get filed as tops by other people, which is worth knowing before you argue with a chart.
Base notes are the slow, heavy materials that last the longest, sometimes for a day or more. Woods, resins and the sweet fixatives: sandalwood, the cedarwoods, benzoin, vanilla oleoresin, tonka, myrrh. Bases do two jobs at once. They give the blend depth and a long tail, and they physically slow down the lighter materials sitting on top of them, so the whole thing lasts longer than its parts would.
Leave out the base and a blend is bright and gone by lunchtime. Leave out the top and it feels heavy and closed from the first second. Both are common first-attempt mistakes and both are easy to fix.
How much of each, and why nobody agrees
Search for a ratio and you will find several, confidently stated and flatly contradicting each other. Three parts top to two heart to one base. Thirty, fifty, twenty. The reverse of both. They circulate because they are easy to remember, not because any of them is correct, and none of them can be, because the answer depends on two things a ratio cannot see: what you are making, and what you are making it from.
What you are making it for
A blend for a diffuser and a blend for skin want opposite shapes.
In a diffuser, everything is evaporating into a room and the whole thing is over within a couple of hours. Brightness is the point, so a top-weighted blend makes sense. Load it with base and you get a heavy, flat room and a diffuser that is a nuisance to clean.
On skin, the base is the entire reason the blend is still there after lunch. The tops are gone within the hour no matter what you do, so a wearable blend is usually weighted the other way, toward the heart and the base. Fine fragrance leans on this heavily: the long materials are the backbone, and the citrus at the opening is a first impression rather than the substance of the thing.
So the honest answer is that a top-heavy ratio is diffuser advice being repeated as though it were perfume advice. If you want to wear it, give the base room.
What you are making it from
This is the bigger variable, and it is the one the ratios ignore completely. Odour strength is not distributed evenly across the note positions. It varies between individual materials by an enormous margin, and no rule about tops and hearts can account for that.
Sweet orange is weak, cheerful and gone quickly, and a blend can absorb six drops of it without blinking. Oakmoss, oud, vanilla oleoresin, benzoin and the absolutes are the opposite. Boronia, tuberose, osmanthus and jasmine absolutes are extraordinarily concentrated, and one drop of any of them will run the whole blend and keep running it for days. Some of the spices behave the same way: a single drop of cinnamon bark or clove bud will take over a twelve drop blend and leave nothing else audible.
Which means the practical version of the rule is not about position at all. Strong, tenacious materials go in small and get added to. Weak, fleeting ones go in generously. If you are working with an absolute, assume you need a fraction of what feels reasonable, and dilute it in carrier first so you can dose it in something finer than whole drops.
Blending is harder than it looks
Worth saying plainly, because most guides imply otherwise. Reading about top, heart and base takes ten minutes. Getting a blend to actually sit together takes a long time, and the structure is only the scaffolding.
Materials interact rather than simply stack. Two oils you like separately can turn sour, muddy or oddly medicinal together, and there is no way to predict it from a chart. A blend that smells right on a paper strip can read completely differently on skin, because your own warmth is part of the formula. The balance shifts as it ages, so the thing you judged on day one is not the thing you will have in a month. And the difference between a blend that works and one that does not is often a single drop.
None of that is a reason to be intimidated. It is a reason to work small, change one thing at a time, write everything down, and expect the first several attempts to be unremarkable. That is not you doing it badly. That is the actual process, and anyone who tells you it is a matter of following a ratio has skipped the part where it gets difficult.
A first recipe worth making
Deliberately not the obvious trio. This one is resinous and herbal rather than sweet and floral, and more to the point, it puts everything above to work. Twelve drops in 30ml of carrier, which is exactly 2 percent:
- 6 drops elemi - the top. Bright, lemony, faintly peppery, with a resin edge underneath. A resin behaving as a top note, which is the first thing on this page that refuses to follow the rules.
- 4 drops Spanish rosemary - the heart. Clean, herbal and a little camphorous. It stops the elemi from reading as merely citrusy and gives the middle of the blend some spine.
- 2 drops benzoin - the base. Sweet, balsamic, close to vanilla. Slow, heavy, and enormously tenacious.
Why the base is the smallest number
Look at that list against everything said above and it appears backwards. A blend to wear on skin, and the base is the smallest figure in it.
Benzoin is why. It is on the list of powerful materials a few paragraphs up for a reason: two drops of it will still be on your skin long after the elemi is a memory, and it is sweet enough that it colours everything around it. Weight this blend the way a base-heavy rule suggests, put five drops of benzoin in, and you do not get a well-structured perfume. You get benzoin, with a faint suggestion of something else that happened earlier in the day.
This is the whole argument in one recipe. Note position tells you when a material turns up and how long it stays. It tells you nothing at all about how loud it is when it gets there. The drop count has to answer to strength, and strength is a property of the individual material, not of the tier it has been filed under. Six drops of a quiet top note and two of a thunderous base can be a perfectly balanced blend, and frequently is.
Two practical notes. Benzoin is thick, slow to leave the bottle, and often sold already cut with a solvent, so check what you have and warm the bottle in your hand before you expect a clean drop. And for a diffuser, run the elemi and rosemary alone, at six and four. Benzoin is sticky enough to gum up an ultrasonic diffuser, and it is not worth the cleaning.
When you want to move it around, change one thing at a time: aussie mint or clary sage in place of the rosemary, lemon in place of the elemi, tonka or vanilla oleoresin in place of the benzoin. That last swap changes nothing structurally, because both are the same kind of sweet, heavy, powerful material. Reach for an absolute instead, boronia or tuberose or osmanthus, and the balance has to be rebuilt from the ground up around a single drop.
Let it rest before you judge it
This is the step almost everyone skips. A freshly mixed blend smells disjointed, and it is not a fair test of anything. The materials need time to settle into each other. Give it a week in a capped dark bottle somewhere cool, then smell it again. Blends with resins or heavier bases can take two or three weeks to properly come together.
Label it with the date and the exact drop counts. You will forget, and the blend you cannot reproduce is always the good one.
Before it goes on skin
Everything above is about proportion and structure, not strength. Anything going onto skin needs to be diluted in a carrier first and patch tested. There is no cold-pressed citrus in the recipe as written, so the sunlight rule does not apply to it, but swap the elemi for lemon or bergamot and it does: keep it low and stay out of direct sun for at least twelve hours after wearing it. Those numbers are all in the carrier-oil starting guide.
Rosemary is also one of the oils that comes with cautions of its own rather than a blanket recommendation. If you are pregnant, or you have a seizure disorder, ask a qualified aromatherapist or your doctor before wearing it rather than working it out from a blog.
Essential oils are for external use only, and none of this is medical advice.
The oils named here are ones I keep in stock, chosen because they are inexpensive and because they demonstrate something, not because they are the easiest possible starting point. A first blend should be something you can afford to get wrong twice, and something you learn from when you do.