What Is a Mod? The Unit of Formula Development
In the perfumer's language a mod (modification) is a changed version of a formula. The first trial formula is prepared, smelled, something is changed and a new mod is born. Until a perfume reaches the market it passes through dozens, sometimes hundreds of mods; each carries a defined difference from the one before.
The mod system takes formula development out of "mixing by feel" and turns it into a manageable process. You see on record which change fixed what and which spoiled what. When you say "that version was better" three months later, you know what that version was.
This article explains how mods are named, how they are recorded and how a trial series is managed. The subject is not formula chemistry but discipline.
Naming: Every Mod Must Have a Single Name
The mod system begins with naming. You set the rule; what matters is that it is consistent and unambiguous.
| Element | Example | Explanation |
|---|---|---|
| Project code | VTV | Short name of the project (a vetiver scent) |
| Series number | VTV-01 | Number of the main skeleton; when the skeleton changes, the series changes |
| Mod number | VTV-01-03 | Third mod of the series |
| Sub-branch (optional) | VTV-01-03a / 03b | Trials branching from the same mod in two directions |
| Dilution mark | VTV-01-03 @15 | Evaluation sample prepared at 15% in alcohol |
Rule: a mod number is given once and never reused. You do not say "I changed VTV-01-03 a little"; what has changed is VTV-01-04. The file name, the bottle label and the notebook entry carry the same name.
The series number is the identity of the skeleton. Replacing vetiver oil with vetiveryl acetate is a mod; abandoning the vetiver accord entirely and moving to a patchouli accord is a new series (VTV-02).
The Mod Record: What Changed, Why, and What the Result Was
Three things are recorded for every mod: the full formula, the difference from the previous mod and the evaluation result. Without these three, the mod system is nothing more than numbering.
- Write the full formula
Every mod is a complete formula in its own right; it is not written as "like 03 but with 2 grams more Hedione". If 03 is lost tomorrow, 04 becomes meaningless.
- Write the difference and the reason
"Hedione 8% → 12%: the opening is closed, it wants air." One line is enough. What the change was and why it was made is worth at least as much as the formula.
- Apply the single-variable rule
Ideally only one thing changes in a mod. If you change three things at once and the result improves, you cannot know which one worked. In urgent cases two changes are acceptable; three is off the record.
- Record the evaluation over time
On the strip at 10 minutes, 1 hour, 4 hours and the next day; on skin at 1 and 6 hours. The same protocol for every mod. "It turned out nice" is not an evaluation; "the vetiver disappears at hour 4" is.
- Decide and mark
Every mod is tied to a decision: continue, stop, branch. A mod marked "continue" is the base of the next one; a mod marked "stop" is closed but not deleted.
- Keep the physical sample
A small bottle of every mod, labelled and in the dark. To be able to say "08 was better" three months later, you need 08 itself, not its record.
Managing the Trial Series: When to Branch, When to Stop
Mods are not a straight line but a tree. Managing the series means deciding where the tree branches and which branch is cut.
Branching. If a mod looks as though it could go in two different directions (fresher or woodier), two sub-branches are opened: 05a and 05b. Both are prepared at the same time and evaluated side by side. Branching turns indecision into a trial.
Stopping. If three mods in a row bring no improvement, the problem is not in the detail but in the skeleton. Instead of continuing to produce mods, go back to the series: change the skeleton, open a new series. If a series of twenty mods still has "something missing", what is missing is not a raw material but the construction.
Going back. If after 09 it is decided that 06 was better, 10 is derived from 06 and the record says so: "10 ← 06". The numbers are chronological; the lineage is on record.
Closing. The chosen mod is marked as a "candidate"; it passes stability, compatibility and IFRA checks; only then does it receive a version number and become the production formula. From that moment the mod system ends and change control begins.
Frequently Asked Questions
The most common questions about mod management.
How many mods does a perfume need?
Isn't changing only one thing per mod very slow?
How many grams of a mod should I prepare?
Should I evaluate mods in alcohol or as concentrate?
Is it necessary to keep old mods?
When should I change the skeleton?
Which mod do I show the customer?
Can I keep the mod system in a spreadsheet program?
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