IFRA Limit or Wax Max Load: Which One Wins?

You have two ceilings on how much fragrance oil goes in a candle, and the lower one wins. One is your fragrance oil's IFRA limit, from its certificate. The other is your wax's maximum fragrance load, from the wax maker's sheet. They are measured against different things, so you have to convert one before you compare. I am a candle maker, not a lawyer, and nothing here is legal advice.

What is each number a percent of?

IFRA's guidance says: "Unless otherwise specified, concentrations are expressed in weight-per-weight percent." So an IFRA limit on a certificate is a percent of the finished product by weight. For a candle, that means oil as a share of the whole candle, wax plus oil.

Your wax's maximum is normally a percent of the wax weight alone. In this guide, the load is a percent of the wax weight, starting from the jar's total fill: wax = fill / (1 + load), and oil = wax x load. See percent of wax or percent of total for why the base matters, and the wax-side maximum for where that number comes from.

How do I convert between them?

If the load is L (as a decimal, of the wax weight), then the oil makes up L / (1 + L) of the candle. Going the other way, if the IFRA limit is C (as a decimal, of the candle), the most load it allows is C / (1 - C) of the wax weight. Every cell below is computed with those two formulas.

So a certificate limit of 6.00 does not mean 6 percent load. It means about 6.38 percent of the wax weight. The gap grows as the numbers grow.

Worked example (made-up numbers)

Say you pour an 8 oz fill. Your wax sheet says a maximum of 10 percent of the wax weight. Your oil's certificate says Category 12 = 6.00. All of these numbers are invented.

1. The IFRA limit allows 0.06 / 0.94 = 6.38 percent of the wax weight (computed).
2. The wax allows 10 percent.
3. The lower is 6.38 percent, so the IFRA limit wins.
4. Wax = 8 / 1.0638 = 7.52 oz. Oil = 7.52 x 0.0638 = 0.48 oz.
5. Check: 0.48 / 8 = 6.0 percent of the candle. That matches the certificate.

Now a second oil with Category 12 = 100, like the oils on CandleScience's and Supplies for Candles' example certificates. The IFRA number is not a limit you can reach, so the wax wins at 10 percent. Wax = 8 / 1.10 = 7.27 oz. Oil = 7.27 x 0.10 = 0.73 oz.

Both are ceilings. Your burn tests and your wax's guidance decide where under them you land.

Why do both limits matter?

CandleScience's own example makes the point. Its Rose Petals oil has a Category 12 maximum of 100, which it calls "well above the maximum fragrance load of my wax," so the wax is the limit there. Another oil could be the opposite. You cannot know without reading both numbers.

IFRA's limit is also not the only IFRA rule. IFRA's guidance says a ban in a Standard "applies to all final product applications, including non-skin contact applications," so a banned ingredient is banned in a candle even when the Category 12 number looks generous. If you are unsure whether an oil contains a banned ingredient, ask your supplier.

What if I am not sure which basis the certificate uses?

IFRA's guidance says weight-per-weight unless the certificate says otherwise. If a certificate states a different basis, follow the certificate. If it states nothing and you are unsure, ask your supplier. Until you hear back, my cautious rule, not IFRA's, is to use the lower reading: treat the certificate number as a percent of the wax weight, which is the stricter way to read it. For the example above, that would cap you at 6.00 percent load instead of 6.38.

Common mistakes

• Comparing 8 percent of the wax with 8 percent on the certificate. They are different bases, and 8 percent of the wax is only 7.41 percent of the candle.
• Checking the wax maximum and forgetting the certificate, or the other way around.
• Checking a blend against one oil's limit. See IFRA limits when blending oils.
• Reading the wrong category. For a candle it is Category 12. See how to read an IFRA certificate.
• Treating either number as a target. For starting loads, see how much fragrance oil per pound of wax.