Carriers & Solvents in Perfumery: Alcohol, DPG, IPM, MCT

Fragrance oil is a concentrate. The solvent is what carries it to the skin, opens it up, and releases it. The right carrier determines clarity, skin feel, and cost all at once. The wrong one brings cloudiness, a greasy film, and disappointment.

Carrier selection must be considered alongside the character of the formula. A volatile, citrus-forward composition and a resinous, heavy accord (a balanced blend of multiple raw materials) do not call for the same solvent. Start by deciding what the product will be: an alcohol-based spray, an oil-based roll-on, or a room fragrance?

In the sections below we will cover four key carriers: perfumer's alcohol, DPG, IPM, and MCT. Each has its own place; the rest is your signature.

Every solvent has a personality. Knowing where each one shines can significantly cut your trial-and-error costs.

Perfumer's alcohol (ethanol-based): Volatile, fast-drying, and the best solvent for projecting scent into the air. It is the backbone of spray fragrances. It typically contains a denaturant and minor auxiliaries; the raw, sharp note known as "alcohol bite" softens with maceration.

DPG (dipropylene glycol): An odourless, non-greasy, economical glycol. Frequently used for diluting fragrance oils and as a base in room fragrances and diffusers. Less volatile than alcohol; can leave a slightly tacky feel on skin.

IPM (isopropyl myristate): A lightweight, dry-touch emollient. It spreads quickly on skin in oil-based fragrances without leaving a greasy film. Its solvency behaviour differs from alcohol, particularly for resinous and woody materials.

MCT (medium-chain triglyceride / coconut-derived oil): A clear, virtually odourless carrier oil. A favourite for roll-ons and body oils. Resistant to oxidation and has a long shelf life; however, MCT does leave a noticeable oily feel on skin.

The values in the table are general tendencies; not every raw material behaves identically in the same solvent. Always test in your own formula.

The most common formulator mistake starts here: a formula that begins crystal clear turns hazy within a few hours.

In alcohol-based fragrances the main culprit is too much water. Adding more water than necessary to high-proof ethanol disrupts solubility; phase separation and cloudiness (hazing) form between the fragrance oil and the water. Keep the water content low — start with very little and check clarity after every addition. If clarity is non-negotiable, use a ready-made perfumer's alcohol or a solvent matched to your formula.

Resinous, balsamic, or certain woody raw materials (for example vetiver derivatives) may not dissolve fully in alcohol. Here IPM or DPG can serve as a co-solvent. If waxy materials precipitate in a formula kept cold, clarity can be restored by cold filtration (filtering at low temperature).

In diffusers and room fragrances DPG usually provides a clear base. MCT oil is inherently clear, and in oil-based products water never enters the equation — there the concerns are oxidation and skin feel, not cloudiness.

One of the most widely misunderstood points: "More fragrance oil = longer-lasting." This is not correct.

Longevity does not depend on concentration alone; the true determining factor is the volatility of the raw materials. A citrus-heavy 25 % extrait can fade quickly, while an amber–oud–musk formula at 10 % can last for many hours. The solvent plays the carrier role; longevity is actually determined by the heavier base notes in the formula and the fixatives.

Concentration classifications such as EDP/EDT only describe the percentage of fragrance oil — they do not guarantee performance. Concentration alone does not determine performance; the structure and volatility of the formula do. Avoid making precise hour-by-hour longevity claims.

The process that softens the raw edge of an alcohol-based fragrance is maceration. Maceration is not merely "leaving it to rest"; through the interaction and esterification between alcohol and fragrance oil, the scent settles and harshness diminishes.

Solvent selection starts with the product category. Spray, roll-on, or diffuser? The decision flows from there.

For a spray fragrance perfumer's alcohol is the main base; a small amount of IPM can be added as a co-solvent for resinous notes. For oil-based roll-ons or attars, MCT or IPM takes centre stage. For diffusers and room fragrances, DPG is an economical and well-balanced choice.

On the topic of safety, avoid absolute statements. "Natural is always safer" or "synthetic lasts longer" are not accurate; safety depends on the level of use. Similarly, IFRA limits are set not according to the total fragrance oil percentage but according to the individual materials and allergens within the fragrance oil and the product category (leave-on / rinse-off).