Fragrance Oil FAQs: Common Questions Makers Ask (Answered)
When you start working with fragrance oils, a lot of little questions tend to pop up along the way.
Things like: how much fragrance to use, why a scent smells different in a product than it does out of the bottle, or how to properly store your oils.
We’ve gathered some of the most common questions makers ask about fragrance oils and answered them below to help you feel more confident when creating.
How long do fragrance oils last?
Most fragrance oils perform best when used within 1–2 years, though proper storage can help extend their lifespan.
Over time, some fragrance oils may slightly darken or thicken, which is normal.
If you’re unsure whether an older fragrance oil is still performing well, the easiest way to check is to test it in a small batch.
Why does a fragrance oil smell different in a product than it does out of the bottle?
This is something a lot of makers notice when they first start working with fragrance oils.
Fragrance oils are designed to perform inside a finished product, not necessarily straight out of the bottle.
Once a fragrance oil is added to wax, soap, or another base, the scent will develop as it interacts with other materials and goes through processes like heating, curing, or saponification.
For example:
- Candle and wax melt fragrances tend to develop more after curing and while melting
- Soap fragrance can change slightly during the soap-making process
- Room sprays and body sprays disperse scent differently once they’re sprayed
Because of this, it’s always best to test a fragrance oil in your actual product before deciding whether it’s the right scent for your line.
What does fragrance load mean?
Fragrance load simply refers to the percentage of fragrance oil used in relation to the total weight of a product.
For example, a candle with a 10% fragrance load contains 10% fragrance oil and 90% wax.
Different products and materials have different recommended fragrance loads, which is why testing is such an important part of the process.
Need help calculating the fragrance load for your products?
Check out our free General Fragrance Load Calculator!
How do you calculate fragrance load for candles or other products?
Fragrance oil is usually calculated using a percentage of the total batch weight.
For example, if you’re making a candle with a 10% fragrance load:
Total candle weight: 16 oz
Fragrance oil: 1.6 oz
Wax: 14.4 oz
Using a digital scale makes this process much easier and helps ensure your batches stay consistent.
Need more help calculating fragrance load? Check out these helpful tools and guides!
How should fragrance oils be stored?
To help keep fragrance oils performing their best, it’s a good idea to store them in a cool, dry place away from direct sunlight.
A few simple storage tips:
- keep bottles tightly sealed
- avoid extreme temperatures
- limit exposure to light and air
Proper storage can help preserve the fragrance and extend its shelf life.
Can you mix fragrance oils together?
Yes! A lot of makers love creating custom scent blends by combining different fragrance oils.
Blending scents can be a fun way to develop something unique for your product line.
If you’re experimenting with blends, it’s
usually best to:
- start with smelling the fragrances together
- write down notes on your preferred ratios
- test the blend in your finished product
Some of the most memorable scents actually come from layering multiple fragrance oils together.
Need further help understanding how to blend? We've got you!
Why does fragrance oil sometimes discolor candles or soap?
Some fragrance oils contain natural components like vanillin, which can cause products to darken over time.
This is especially common in scents with notes like:
- vanilla
- caramel
- chocolate
- bakery-type fragrances
While the color of the product may change, it usually doesn’t affect how the fragrance performs.
Many makers simply plan their product colors around fragrances that are known to discolor.
Why does my fragrance smell weak in my product?
There can be a few different reasons why a fragrance might seem weaker than expected.
Some common factors include:
- using too little fragrance oil
- not allowing candles or soaps to fully cure
- the type of wax or base being used
- environmental conditions during testing
- the fragrance oil itself (not every scent is intended to be extremely strong!!)
- using the incorrect wick size (for candle making)
Sometimes a little adjustment to fragrance load (within IFRA limits) or allowing more cure time can make a big difference.
Check out or guide for candlemakers on this topic:
FAQ: My candle has weak hot throw or cold throw- what should I do?
How should I weigh my fragrance oil?
You should always measure fragrance oils by weight (using a scale) rather than by volume because each fragrance oil has a slightly different density. (This is how we sell fragrances- by weight!!)
Measuring by weight keeps your fragrance load accurate and consistent when you’re formulating products.
For example, when making candles, soaps, or room sprays, fragrance oil percentages are calculated based on the total weight of the formula, not the volume.
Using a digital scale is the easiest way to make sure your measurements stay consistent from batch to batch.
Can you use fragrance oils in multiple types of products?
Many fragrance oils can be used across a variety of product applications, including things like candles, soap, room sprays, and personal care products.
That said, not every fragrance oil is suitable for every type of product.
Each fragrance has specific safety limits depending on how it’s being used.
Before formulating with a fragrance oil, it’s always important to check the IFRA document to confirm the maximum usage levels allowed for the type of product you’re making.
More resources:
Why do some fragrance oil bottles look fuller than others?
Like we talked about above: fragrance oils are filled by weight, not volume.
Because fragrance oils have different densities, some oils are heavier while others are lighter.
A heavier oil may take up less physical space in the bottle, while a lighter oil might appear to fill the bottle more.
Even though the bottles might look slightly different, each fragrance oil still contains the correct labeled weight.
Do I need to check IFRA documentation before using a fragrance oil?
Yes! Checking the IFRA document is an important step whenever you’re working with fragrance oils.
IFRA (International Fragrance Association) guidelines outline the maximum safe usage levels for fragrance oils across different product categories, such as candles, soap, or body products.
Each fragrance oil has its own IFRA sheet that shows the safe usage percentages depending on the type of product you're making.
Taking a moment to review this document helps ensure your formulation stays within safe limits and performs the way it should in your finished product.
More resources:
Why do my fragrance oils look like they have crystals at the bottom of the bottle?
As I mentioned above, fragrance oils should be stored in a cool space, but during shipping, temperatures are not regulated and your package might meet some extreme temperatures.
The crystals you see in the bottom of your bottle is called crystallization, and it usually happens in colder months when the fragrance oil gets too cold!
We have a dedicated blog post for this that explains more about crystallization and how to fix that issue!
That's about it for fragrance oil FAQs!
To wrap things up, fragrance oils can sometimes feel a little intimidating to use when you’re first working with them- if you feel this way, I promise, you aren't alone. We've all been there!
But testing, measuring accurately, checking IFRA guidelines, and giving your products proper cure time will go a long way in helping you get the results you’re looking for.
As you keep experimenting, you’ll start to learn how different fragrances behave in your own recipes and processes.
And honestly, that’s part of the fun- every batch teaches you something new!
Take any 'failure' as a lesson and use it as a stepping stone on your journey.
You've got this!
Do you have any questions about fragrance oils? Drop them in the comments below on this blog and we will try to help!
Hi! I'm Kenna!
Co-founder of Midwest Fragrance Company, business builder since 20, fueled by coffee and grounded by yoga. I’ve learned (mostly the hard way) what it takes to grow a maker business, and I share those lessons here… the real ones, not the highlight reel.
At MWFC, we sell all the supplies you need to create scented products that truly shine ✨
Want to keep following along? Find us on Instagram @midwestfragranceco
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