How to add fragrance to cold process soap?

To add to the user experience of handmade soap beyond the looks and the benefits is often the scent of the soap. A scent ties into the human brain to the point that it solidifies memory according to Choosing the right fragrance is one thing but knowing how to incorporate into your soap is another.

Generally there are two ways to add fragrance to cold process soap that works best. Add your fragrance to your base oils before adding your lye water and secondly adding your fragrance at light trace. Its good to know both techniques as you may have to switch between the two.

Fragrance oil essential oil for cold process soap

Fragrance vs essential oil

There are pros and cons to using either fragrance oils or essential oils to add scent to your soap. These pros and cons can take a long time to debate as there are so many different types of fragrances on the market compared to essential oils.

The best way to consider which is best for your soap is know the difference between the two as there are major differences in how they are made and how they affect the overall soap.

Fragrance Oil

Fragrance oils are.. for lack of a better phrase, man made. They are developed by scentcrafters that mix and match various scents and techniques to come to a predetermined fragrance.

A good example of this is the musk from beavers are used to make certain perfumes, just as ambergris is a substance that whales “vomit” into the ocean that washes up on the beach and is used in making of perfume.

The beauty of fragrance oils is that there are almost a limitlessness amount of combinations that can be made. Then beyond the actual base fragrance a number of fragrances can be blended by the soaper to make a unique scent.

Scents found in nature are difficult to capture their true essence, hence scentcafters do their best to mimic these fragrances. A good example of this would be the scent of a freshly cut lawn after a rain shower. A rather difficult mixture of scents but it can be recreated.

These types of fragrances can be made to be added to soap to enhance the user experience while using handmade soaps.

However there is a drawback. Many fragrances do not always behave well in soap making, we will cover this below under Scent Behavior.

Essential Oil

Unlike fragrances, essential oils are the essence of natural items. These fragrances are extract of mainly trees such as eucalyptus, sage, rosemary and tea tree.

The process to extract the scent of a plant is exhaustive as bundles of materials are needed just to make a small amount. This is the nature of natural essential oils.

The process may differ from plant to plant but the results are generally the same. You have a fragrance that is derived from nature and in many cases that oil comes with some natural benefits as well.

Due to the extraction of plant matter to make essential oils, there are a limited amount of essential oils on the market. Far less than the standard fragrance oils. Keep this in mind when making your scent selection.

Fragrance oil essential oil for cold process soap

What tools to use to add fragrance to soap

Essential fragrance oils do hold certain properties that you must be aware of. These properties make adding the scent to your soap tricky. If you use the wrong tool you could damage the tool or even its container.

Glass for essential oil

A side effect of essential oils as fragrance is that the oils can be corrosive. You will notice on many labels a warning stating to not apply directly to your skin. This is due to the potency of the essential oil and how it can cause skin damage if applied directly to the skin.

Not only is your skin in the danger zone but also the container you use to measure out your essential oil. Essential oil and plastics do not work well with each other. In fact essential oils will eat away at plastic weakening it or breaking even hard commercial grade plastics.

For this reason it is suggested that you store and measure out essential oil using glass. Small glasses work great or if you prefer a measuring cup the pyrex tempered measuring glass works well.

Hard plastic for fragrance

Fragrances are not as corrosive as essential oils hence the use of plastics are accepted. However long use of plastics does have its drawbacks.

What tends to happen over time is that the chemicals used to make certain frangrances seep into the plastic container. Then other fragrances tend to seep in and push out what ever scent was in another fragrance. This tends to change the overall smell of your fragrance.

This happens and can be seen easier when it comes to fragrances with vanillin in it. Vanillin is contained in vanilla and is the substance that has a tendency to turn soap brown.

Glass again is the best long term solution for fragrance oils.

Pipettes or dropper for mp

Melt and pour soap differs from cold and hot process soap in that it requires very little fragrance. A 2lb mold of cold or hot process soap will require about 2oz of fragrance or essential oil. However the same 2lb of melt and pour soap will require about a teaspoon which is about 0.17 ounces. yeah that little.

To measure out such small amounts of fragrance we found that pipettes are the best tool for the job. They have measurement markers which makes it easy to read and ensure you add the right amount.


Pipettes are made of plastic and as I stated earlier plastic and essential oils don’t work well long term. You may get a few uses out of it when using essential oils.

The same issue comes into play with fragrance oils where some of the past fragrance oils gets trap in the pipettes and is carried out into your next batch. This is negligible and usually never noticeable but its good to know over long term.

The good news is the pipettes are relatively low cost so you can have many on hand at one time before you run out.

Fragrance oil essential oil for cold process soap

Fragrance behavior in cold process soap

Very important information

Before you begin to add scent to your soap you MUST learn how the scent will behave in your soap. When you see the statement “behaves well” in cold process, hot process or melt and pour soap then there is nothing you have to worry about.

The problem comes when under the behavior of a fragrance there is information. This is where you should pay attention.

Accelerate or Discolor

The two main “bad” behaviors of fragrance in soap are acceleration and discoloration.

Acceleration is the worst behavior and can be frustrating if you do not prepare for it. What is meant by “accelerates trace” is that when you add that particular fragrance to your soap mixture it will chemically heat up and begin to saponify your soap quickly.

This can be a major issue if you want to do swirls, or other techniques that require you to have some time on your hand.

Acceleration can also lead to false trace if you do not mix the fragrance well into the batter. False trace will look good to the eye but your soap will not set in the mold and begin to separate in a cheesy fluffy ball of soap batter.

When you use a fragrance that accelerates trace ensure that you are making a soap that does not require any special technique like swirling or piping or anything technical. Just keep is simple one color or no color mix an pour.

fragrance oil brown behavior

Discoloration is another behavior issue with certain fragrances. This one is easier to work with however. Discoloration that normally occurs will be your soap turning brown. This is due to the presence of vanillin.

Yes vanillin not necessarily vanilla. However vanilla contains vanillin but synthetic or lab vanilla can be made to reproduce the scent but not the effects.

The vanillin reacts to the oils as it saponifies turning the overall soap brown. This can be useful if you want a brown soap but you must be careful of adding another color expecting it to stay the way it should be.

Add Fragrance to base oil in cold process soap

The easiest, quickest and best way to add scent to your soap is to add the scent, whether its an essential oil or fragrance oil directly to the base oils.

This method ensures that the scent is evenly distribute within the end soap. It is the quickest way to add scent and allows you to focus on other techniques like adding color or additives.

Take note however how the scent behaves in your soap. If it is a fragrance that will accelerate trace just be prepared to have a short stick blending portion of work and keep your soap mold nearby.

If the fragrance discolors the soap and you have no issue with the discoloration then adding it at this stage will not be a problem either.

Add fragrance to the soap batter of cold process soap

The second method is to add the scent to the batter at a light trace. This takes more time and is a medium technique to carry out.

Here is what happens. If you do want to make layers or swirls and even add color with a fragrance that accelerates trace. The fragrance will be the last ingredient before you carry out your technique and add your batter to the mold.

Drop swirl example

A good example of this. Lets say you want to do an in the pot swirl but the fragrance will accelerate trace. You will follow these steps

  1. Add your lye water to your batter and take the mixture to emulsification ( this is pre trace)
  2. Separate the amount you will use to perform the in the pot swirl. (this is often the less of the two that will make the swirl)
  3. Take the drop swirl batter and continue to mix to a light trace and add the color that you will want for your swirl. (leave at a light to light medium trace)
  4. With your emulsified batter in the bowl/pot, mix it to a light trace – be prepared to work quickly
  5. Add your primary color and mix with a whisk and light stick bending (this keeps the batter at a light trace while mixing your color well)
  6. Add the fragrance into the pot mixture and stir with a whisk vigorously. Follow up with a few burst of the stick blender. ( at this time the fragrance will have begun to work on the batter accelerating the light trace to a medium tract)
  7. Perform the drop swirl technique into the bowl/pot and pour into your mold.

Notice with this technique you only added the accelerated fragrance to the larger soap batter mixture. With a swirl technique the majority of the soap will have the fragrance hence the smaller drop batter will not but will not be noticeable as not having any scent.

Fragrance oil essential oil for cold process soap

Final Thoughts

Adding a scent to your cold process soap is very difficult once you have and idea of the difference between essential oil and fragrance oil as scents.

Keep in mind how the fragrance behaves in the soap and you will not run into much issues. Essential oils pretty much behave well in cold process soap so there is not much to worry about there.

I personally find it easier if I am making a cold process soap with one essential oil and one color to add the color and the essential oil to the base oils and begin making my soap from there.

Play with a few techniques to find out which works best for you, add scent to the base oils or add at light trace.

Recent Posts