A candle can smell wonderful in the jar and then barely register once it's lit. Usually the wax isn't at fault, and neither is the oil. It's the ratio between them. Fragrance load — how much oil you add, measured as a percentage of your wax — is one of the few variables in candlemaking that changes everything at once: scent throw, burn quality, how the wax sets, and whether the finished candle is safe and legal to sell.

Get it roughly right and your candles smell like the bottle. Get it wrong in either direction and you'll be wondering why your kitchen smells of nothing while the surface of your candle looks like it's been left out in the sun.

What fragrance load actually means

Fragrance load is the weight of fragrance oil expressed as a percentage of the weight of wax. Weigh 200g of wax, decide on an 8% load, and you'll add 16g of oil. Total wax-and-oil weight: 216g. That's it. No mystery.

There is, however, a second convention worth knowing about. Some makers calculate the load as a percentage of the finished weight rather than the wax weight. In that case, 8% of 216g is roughly 17.3g of oil — a small but real difference. Neither method is wrong, but you need to know which one you're using. Pick one, write it at the top of your batch sheet, and stick to it. If you're following someone else's formula, ask before you assume.

Typical fragrance load ranges by wax

Every wax has a ceiling, and it's usually lower than beginners expect. These are the sorts of ranges you'll find on technical data sheets:

  • Container soy wax: commonly a maximum of 6–10%, with 6–8% the happy place for many oils.
  • Coconut and coconut-soy blends: often hold 8–10%, which is part of why they're popular with makers chasing a strong cold throw.
  • Paraffin: typically 6–10%, with some blends rated higher.
  • Pillar and mould waxes: usually 3–6%. Push higher and the candle can soften, slump or sweat.
  • Beeswax: a dense, hard wax that takes a low load, often 3–5%.

Treat those numbers as ceilings, not targets. A wax rated to 10% is not telling you that 10% is a good idea — only that the wax will physically hold it without falling apart. Always check the data sheet from the supplier you actually bought from, because formulations change without much fanfare.

Why more oil isn't automatically stronger

Wax can only hold so much fragrance. Once it's saturated, the extra oil doesn't go into the air — it migrates back out. You'll see it as an oily sheen on the top, a greasy ring around the inside of the jar, or beads of oil weeping through the surface. Vanilla and heavy resinous oils are the usual suspects.

There's also the matter of cold throw versus hot throw. Cold throw is what you smell from an unlit candle; hot throw is what fills the room as it burns. They don't move together. A high load often boosts cold throw dramatically while doing surprisingly little for hot throw, because oil that isn't properly bound in the wax burns off inefficiently. Past a certain point you're making a candle that smells great on the shelf and disappointing once lit — and paying more for the privilege.

How fragrance load changes the burn

Fragrance oil is not inert. It softens the wax, shifts the melt point slightly, and changes how the melt pool behaves. Change your load and you may have invalidated the wick you spent two weeks testing.

The classic sign of too much oil is a wick that drowns. The flame shrinks, the pool never reaches the edge, the wax tunnels down the middle, and you end up with soot on the glass. Too little oil has its own problem: a clean burn and barely any scent. Some oils also discolour wax over time — pale soy can drift towards yellow or brown with certain fragrances, and no amount of wick testing will fix that.

Cure time sits in the middle of all this. Soy blends generally need one to two weeks after pouring before the scent settles and the hot throw reaches full strength; some makers leave them longer. Testing at day two and declaring the load a failure is a wasted candle.

Safe limits, documentation and labelling

The maximum on your wax data sheet is only half the picture. The other half comes from the fragrance supplier. IFRA standards set maximum usage levels for many fragrance materials, and those levels differ by product type — a candle is not the same as a reed diffuser or a lotion. Ask your supplier for the recommended usage rate and the IFRA documentation for the oil you're using, then work to the lower of the two limits: the wax ceiling or the fragrance restriction.

If you sell your candles in the UK, chemical labelling rules apply. Fragrance allergens present above set concentrations must be declared on the label, and hazard warnings may be required depending on the oil and the concentration. That's a compliance job, not a guess. Check the current requirements and take professional advice where it matters rather than relying on what worked for someone else three years ago.

A practical method for getting the numbers right

  1. Weigh your wax into the pouring jug and write the figure down.
  2. Choose a load inside your wax's range. For a first test, 6% with soy or 8% with a coconut blend is a sensible start.
  3. Do the sum: wax weight × load ÷ 100. Weigh the oil on scales that read to 0.1g — a 1g error at 200g is half a percentage point.
  4. Melt the wax to the temperature your supplier recommends, then let it cool to the fragrance addition temperature, often around 60–65°C for soy blends.
  5. Add the oil and stir gently for about two minutes. Stir, don't whisk; you want an even mix, not air bubbles.
  6. Pour at the recommended temperature and leave the candles undisturbed to set.
  7. Cure before you judge anything — a week for paraffin and blends, two for pure soy.

Finding your own number

Test properly and the answer will present itself. Make three or four small candles from the same wax, jar and wick, varying only the load — say 6%, 8% and 10%. Same oil, same cure, same room. Burn each for a few hours, note the melt pool, the flame height and how far the scent actually travels. Then adjust the wick for whichever load wins.

Your correct fragrance load is the one that gives a full melt pool, a steady flame and scent that reaches the other side of the room without a slick of oil on the surface. Keep notes on every batch, because the number shifts with each new oil you try — and the second candle will be better than the first.

Photo: Alesia Kozik / Pexels