Candle Wicks, Fragrance Load and IFRA Limits: A Guide for Private Label Candles and Diffusers

A candle's wick, wax and fragrance load have to be tested together, because changing one changes how the others perform. The fragrance load is capped by the lowest of three limits: what the wax can hold, what the IFRA certificate allows for that fragrance in candles, and what still burns cleanly in testing. Reed diffusers sit in a different IFRA category from candles, so never reuse a candle limit for a diffuser.

This guide is for brand owners and buyers developing private label candles and reed diffusers. It explains how wicks are chosen, how fragrance load is set, how to read an IFRA certificate and what a manufacturer should document. It is general guidance, not legal advice. Check the current rules with your importer or a compliance adviser.

How wick, wax and fragrance work together

A candle burns melted wax drawn up the wick, not the solid wax. The wick has to deliver enough fuel to keep a steady flame and form a full melt pool, without pulling up so much that the flame grows tall, smokes or soots. Fragrance oil changes the wax's viscosity and how it burns. Dyes and additives change it again. That is why a wick that works in one scent can fail in another, even in the same vessel.

Choosing the wick

Wick choice depends on four things:

• Vessel diameter and shape. Wider vessels need larger wicks or more than one wick. Tapered or narrow-necked vessels change airflow.
• Wax type. Plant waxes such as soy are more viscous and usually need different wick sizes from paraffin. See our wax types guide.
• Fragrance and dye. Heavier fragrance oils and higher loads can clog a wick.
• Wick construction. Flat braided cotton, cored cotton, paper-cored and wooden wicks each burn differently and suit different looks.

The usual method is to pour test candles across a series of wick sizes and burn them. Each test looks at flame height, melt pool, soot, mushrooming, vessel temperature and how the candle behaves at the end of its life.

Lead in wicks

In the United States, the US Consumer Product Safety Commission bans metal-cored candlewicks containing more than 0.06% lead by weight of the metal, and candles made with them. The CPSC guidance also covers related shipping statements and certificates. Buyers in most markets ask for confirmation that wicks are lead-free, so keep the wick supplier's specification on file.

Setting the fragrance load

Fragrance load is the percentage of fragrance oil in the finished wax. Three limits apply, and the working load is the lowest one that still gives the throw you want.

1. The wax limit. Each wax supplier states a maximum fragrance load. Above it, oil can seep to the surface or pool under the wax.
2. The IFRA limit. The fragrance's IFRA certificate states the maximum concentration for each product category. For some fragrances the candle category has no practical cap, but for others it does.
3. The burn limit. Too much fragrance for the wick can cause smoke, soot, a large flame or a drowned wick. Burn testing decides this.

More fragrance does not always mean stronger throw. Throw also depends on the wax, the wick, the curing time and the fragrance itself. A well-matched candle at a moderate load often outperforms an overloaded one.

Reading an IFRA certificate

The IFRA Standards are the fragrance industry's system for the safe use of fragrance ingredients. They can ban, restrict or set specifications for materials, and they are mandatory for IFRA members. At the time of writing, the 51st Amendment is in force and IFRA has closed consultation on a 52nd Amendment. Ask your fragrance house which amendment each certificate refers to.

An IFRA conformity certificate for a fragrance usually shows:

• The fragrance name and code.
• The IFRA amendment it was assessed against.
• A table of product categories, each with a maximum concentration for that fragrance in the finished product.

Candles are commonly placed in Category 12, which covers products not intended for skin contact. Reed diffusers are commonly placed in Category 10A under recent amendments, and limits in that category are often much lower than in Category 12. IFRA states that categorisation is ultimately the producer's decision, so confirm the category with your fragrance supplier for every product type in the range. Use the diffuser row for diffusers and the candle row for candles. Room sprays sit in their own category again.

IFRA is not the whole compliance picture

An IFRA certificate shows the fragrance is used within the industry's safe use limits. It does not by itself cover a market's chemical labelling rules, its product safety rules or fire safety. In the EU and Great Britain, for example, sensitising fragrance ingredients can trigger allergy statements or hazard labels on the candle. Fragrance suppliers provide safety data sheets and allergen information to support those decisions. Read our EU candle labelling guide and our US guide for market detail. Our UK guide covers Great Britain.

Reed diffusers: a different balance

A reed diffuser has no flame. Fragrance rises through the reeds by capillary action and evaporates from the tips. The variables are:

• Base. The carrier that dilutes the fragrance and controls evaporation.
• Fragrance concentration. Capped by the Category 10A limit on each fragrance's IFRA certificate.
• Reeds. Material, length and number change how quickly fragrance travels.
• Bottle opening. A narrow neck slows evaporation and reduces spill risk. See our bottles range.

Because diffuser limits can be low, some fragrances that work well in candles are not practical in diffusers. Check this early if you want the same scent across candles and diffusers.

A sensible testing sequence

Which formal tests to run, and where, is agreed with your importer. We keep a record of the wick, wax, fragrance code, load and test results for each approved sample, so the production batch matches what you signed off.

What to send us with a brief

• Scent direction, or a reference fragrance from our essential oil blends or diffuser oils.
• Vessel or bottle size and shape, or a request for options.
• Wax preference and target markets.
• Products in the range: candles, reed diffusers, room sprays.

We develop each product to your brief and quote per brief. See the full service on our private label candle manufacturing page or start a conversation through our contact page.

Frequently asked questions

What is a normal fragrance load for a candle?

There is no single figure. The wax supplier states a maximum the wax can hold, the IFRA certificate states a maximum for the fragrance in candles, and burn testing shows what actually performs. The working load is the lowest of the three that gives the throw you want.

Which IFRA category applies to candles and reed diffusers?

Candles are commonly placed in Category 12 and reed diffusers in Category 10A. IFRA notes that categorisation is ultimately the producer's decision, so confirm the category with your fragrance supplier and read the matching row on the certificate.

Does an IFRA certificate mean the candle is legal to sell?

No. The IFRA certificate covers safe use of the fragrance. Market rules on labelling, chemical classification and product safety still apply to the finished candle, and fire safety is shown by testing.

Why does my candle tunnel or smoke?

Tunnelling usually means the wick is too small for the vessel and wax. Smoke, soot and a mushrooming wick usually mean it is too large, or the fragrance load is too high for that wick. Both are fixed by re-testing the wick series.

Do you use lead-free wicks?

Wick type is selected and documented per brief. In the US, metal-cored wicks above the CPSC lead limit are banned, and buyers in most markets ask for confirmation that wicks are lead-free. We share wick specifications with your importer.