My Candle Needs a Larger Wick After I Switch Fragrance Suppliers Even Though Both Products Have the Same Scent Name — Why?

A scent name describes a smell, not a formula

You changed suppliers for an oil you have used for months. The name on the new bottle matches the old one, the smell is close, and you poured it into the same wax, jar and wick at the same load. The candle now needs a larger wick to burn properly: the flame looks small, the melt pool creeps outward too slowly, or the wick struggles to keep up. It feels as though the new oil is faulty. More often, it is simply a different formula that happens to share a name.

A fragrance name such as vanilla, sandalwood or lavender tells you what the oil is meant to evoke. It says nothing about which aroma materials were used to build that impression, in what proportions, or what they were diluted in. Two perfumers asked to build a vanilla can reach a similar smell with very different ingredient lists: one leaning on vanillin and sweet resins, another on lighter, creamier materials with a musky base. In a bottle they may be hard to tell apart. In a wick, they are different fuels.

This is why a proven wick is really proven for a specific formula, not for a scent family or a product name. When the formula changes, the approval lapses, even if nothing else in your process did.

Which properties of the oil change what the wick needs

Several characteristics of a fragrance oil influence how it moves up a wick and how it burns once it reaches the flame. You will rarely get full formula disclosure, but understanding these properties helps you ask better questions and read your test results.

Viscosity and heaviness

Thicker, heavier oils travel up the wick less readily than light ones. If the new oil is more viscous, the flame can receive less fuel than it did with the old oil, which appears as a smaller flame and a slower melt pool. A larger wick compensates by drawing more fuel. Base-heavy compositions built on resins, woods or crystalline sweet materials tend to fall in this category, though the only reliable check is your own burn.

Volatility of the lightest components

A published flashpoint is the temperature at which vapour from the oil can ignite, and it is mainly a handling and safety figure. A lower figure often indicates a larger share of quick-evaporating material, while a higher one suggests the composition is weighted towards slower materials. It is not a burn prediction on its own, but a large difference between old and new oils is a signal that their behaviour in the melt pool may differ.

Vanillin and similar materials

Vanillin-rich oils are associated with carbon build-up and, in some systems, with wicks that struggle. They are also the usual cause of yellowing in light wax. If the new vanilla carries more vanillin than the old one, both the wick and the colour may change.

Diluents and concentration

Some oils are more concentrated than others, and some include carrier materials. A more concentrated oil may reach the same scent strength at a lower load, which changes the wax-to-oil ratio if you keep your old percentage. The same percentage of two oils is therefore not the same fuel, and not necessarily the same experience in the room either.

Even one catalogue shows how far same-family oils differ

You do not need to compare two suppliers to see this. Within CSI's own range, three oils carry vanilla in their names, and their product pages publish different specifications. The table uses only those published figures.

Vanilla Bean and Dark Vanilla share a price and a family, yet one is described as rich vanilla and spice over caramel and cream with a dark amber and musk base, and the other publishes a single 203°C flashpoint and a 2.5% vanillin figure. Cinnamon Vanilla sits over 70°C lower in published flashpoint than Vanilla Bean. A wick approved for any one of these would need re-testing for the others, which is exactly the situation you are in after changing supplier.

Re-qualify the wick instead of guessing a size

Treat the new oil as a new fragrance, not a replacement part. That means a fresh wick test in your jar and wax, starting from your current wick and stepping in both directions.

Here is what a small re-qualification costs using CSI Vanilla Bean as the new oil in CSI 464. Six 200 g candles at 8% need 6 × 16 g = 96 g of oil, so the 100 g pack at ₹790.00 covers it. Oil per candle is 16 g × ₹7,646.00 ÷ 1000 = ₹122.34. Wicks for two candles of each option: 2 × ₹5.90 + 2 × ₹9.44 + 2 × ₹12.00 = ₹54.68. Wax for six candles is 6 × 184 g = 1,104 g, and 1104 g × ₹507.40 ÷ 1000 = ₹560.17. The total, excluding jars, is ₹790.00 + ₹54.68 + ₹560.17 = ₹1,404.85. That is modest insurance before you commit a production run to a new source.

What to ask before you switch, and how to decide

Before buying in quantity, ask the new supplier for the information that helps you predict change. CSI, for example, provides IFRA and MSDS documents on WhatsApp request, and its product pages publish flashpoint and vanillin figures where known. Whichever supplier you use, ask for the same set.

Once the test is done, the decision has three parts. If the new oil burns cleanly on a thicker wick and the throw is at least as good, adopt it and update the card. If it needs a thicker wick and a higher load to match the old candle, compare cost per candle honestly, including the wick. If it cannot match the old candle's burn at any reasonable setting, the name was the only thing the two oils shared, and it is worth keeping your previous source for that product.

Where this page fits

CSI already has guides that cover parts of this question. This page answers the specific oil-in-wax question above; these go deeper on the rest:

Three things to buy for this job

Frequently asked questions