How to Dilute Perfume Materials

Ah, perfume making! It’s so romantic, so poetic…so FULL OF MATH.

Why dilute?
Perfumers often need to dilute their materials to 20%, 10%, or sometimes even 1% or .5% or more before adding them to a blend. This serves a number of purposes – from wasting less material while blending to making it easier to work with trace amounts of strong-smelling materials.

What material to use as a diluting agent?
Typically, you’ll want to dilute in perfumer’s alcohol. You should dilute in whatever medium you would be working in – so if you are making oil-based perfumes, dilute in oil. Some people prefer to dilute in Dipropylene Glycol (DPG), which is a common odorless solvent that is completely soluble in water, alcohol, and some oils – and it also is a humectant (attracts water) and has fixative properties. A strictly all-natural perfumer will not want to use DPG since it is a synthetic, but if you’re concerned about safety, don’t be. According to the Environmental Working Group, DPG is safe / very low risk.

Use Weight/Weight Dilutions
An important consideration is that when professionals are talking about dilutions in the perfume industry, they are talking about diluting by weight rather than by volume. So assume all dilutions on any materials you purchase or for any formulas are listed in weight/weight.

Creating a Dilution from Materials at 100% Concentration
Creating a dilution from 100% pure raw material is relatively straightforward.  In the chart below are the ratios in generic “parts” – this would work for drops, ml, grams, etc. as long as you keep the units of measure consistent – but as I mentioned, most professional perfumers work by weight (grams) – so let’s assume this is grams.

If you don’t want to do the math, here is a weight/weight dilution calculator.

You can also check out this nice tutorial on dilutions and blending from Chris of Pell Wall Perfumes. He gives a very thorough step-by-step approach.

Aroma Material Dilutant Total Parts Percent Dilution
1 1 2 50%
1 2 3 33%
1 3 4 25%
1 4 5 20%
1 9 10 10%
1 19 20 5%
1 99 100 1%
1 199 200 ½%

Creating a Dilution from Materials at Different Concentrations
What if you want to do something a little more complicated? For example, I have a bottle of Benzoin Absolute pre-diluted to 50%.  I have a perfume formula that calls for Benzoin at 20% dilution.  How do I dilute a 50% solution to 20%? (These are the questions that make former English majors clutch their heads in agony and wish they’d paid a little more attention in Chemistry lab.)

Well, it turns out there’s a relatively straightforward formula for this: C1V1=C2V2.  C=Concentration and V=Volume. Now, I don’t want to do this by volume – I want to do it by weight. If I wanted to be super accurate, I should probably take into account molecular weight. But since the amounts I’m dealing with are relatively low and I don’t need to be that insanely accurate, I’m not going to worry about molecular weight. (Also, if a chemistry person is reading this and wants to explain how to do this absolutely properly, I’m all ears! Please comment!)

Okay! So let’s figure this out. How do we dilute a 50% solution to a 20% solution? I’m about to do some math. If, like me, math makes your head hurt – you can skip the pain and go use this handy-dandy dilution calculator.

But hey, if you want to see how the math works, here goes. I already know my concentrations. All I have to decide is what final weight I’d like to end up with. For kicks, let’s decide on 5 grams final weight.  So!  Here’s how it would work out:

C1W1=C2W2

    • C1 = 50% = .5
    • W1 (the weight of the 50% solution to add) = unknown
    • C2 = 20% = .2
    • W2 = 5 grams

.5(W1)=.2*5g
.5(W1)=1g
W1=2g

So, okay – now I know that I need 2 grams of my starting 50% solution, and I want to end up with a final weight of 5 grams. So 5 grams – 2 grams = 3 grams. Which means I need to add 3 grams of my diluting agent (alcohol) to 2 grams of the 50% material to get 5 grams of 20% material. Or…

Starting % Ending % How many grams First solution? How many grams diluting agent to add? How many grams final solution?
50% 20% 2g 3g 5g

That’s it! Do you have a better method for calculating dilutions? If so, please comment! I’d love to hear from you.

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Measurement Conversion Chart

When working with essential oils, the most common conversions you typically need are:

  • 20 drops = 1 ml
  • 100 drops =1 tsp = 5 ml
  • 300 drops = ½ oz = 15 ml
  • 600 drops = 1 oz = 30 ml

But, sometimes a little more detail is in order:

Drops Teaspoons Ounces Drams Milliliters
10 drops 110 tsp 160 oz ~18 dram ~½ ml
12 12 drops 18 tsp 148 oz 16 dram 58 ml
25 drops ¼ tsp 124 oz 13 dram 1 ¼ ml
50 drops ½ tsp 112 oz 23 dram ~2 ½ ml
100 drops 1 tsp 16 oz 1 13 dram ~5 ml
150 drops 1 ½ tsp ¼ oz 2 drams ~7 12 ml
300 drops 3 tsp ½ oz 4 drams ~15 ml
600 drops 6 tsp 1 oz 8 drams ~30 ml
24 tsp 8 tbsp 4 oz ½ cup ~120 ml
48 tsp 16 tbsp 8 oz 1 cup ½ pint
96 tsp 32 tbsp 16 oz 2 cups 1 pint

Source: Aromatherapy: A Complete Guide to the Healing Art by Kathi Keville and Mindy Green.

This chart makes the common assumption that 20 drops = 1 ml. However, always remember that drops vary in size based on liquid viscosity and the dropper or pipette you are using. If you want certainty, conduct a test with a calibrated beaker to see how many drops = 1ml.

For example, in Mandy Aftel’s book, Essence & Alchemy, she assumes that 40 drops = 1ml. Double the common assumption! I recently tested this myself using a glass eyedropper and found it to be absolutely accurate. So definitely check before moving forward with a recipe or formula.

Eden Botanicals offers a more detailed range for how many drops = 1 ml, and so far this matches my experience as well:

1 ml = 30-50 drops, depending on viscosity and size of the drop; aprox. 40-50 drops per ml for very mobile oils such as some citrus oils and fir needle oils; more viscous (thicker) oils such as Vetiver and Sandalwood will be approx. 30-40 drops per ml.

1 oz = 30 ml. Using these measurements, it can be extrapolated that there are approx. 900-1500 drops per ounce.

Notice how there are more than double the number of drops in the first estimate (600 drops = 1oz) and the Eden Botanicals estimate (900-1500 drops = 1oz)? Yikes.

This variability is why professional perfumers measure in weight with accurate lab scales. Still, if you’re just messing around at home, drops are far easier and most beginner recipes are calculated in drops. For more conversions, try this handy Volume Unit Converter site.