The blue one. Well studied, genuinely fussy, and the peptide that most rewards being formulated properly.
GHK-Cu is a tripeptide — glycine, histidine, lysine — bound to a copper ion, and it is the reason a handful of serums on the market are bright blue. It occurs naturally in human plasma, it has been studied since the 1970s, and it has more literature behind it than any other peptide in cosmetic use.
It is also the most particular ingredient in this series. Get the company wrong and you waste it entirely.
At a glance
| INCI | Copper Tripeptide-1 |
|---|---|
| What it is | Active — copper-bound signal peptide |
| Solubility | Water soluble (sold as a powder or a 1% solution) |
| Where it goes | Water phase, added at cool down |
| pH | Best 5.0 – 6.5 |
| Usage rate in the guides | 0.1% of the pure powder |
| Charge | Cationic |
| Shelf life | 1 year, refrigerated, protected from light |
What it does
The copper is not decorative. GHK-Cu delivers copper into skin in a bound, tolerable form, and copper is a required cofactor for lysyl oxidase — the enzyme that cross-links collagen and elastin into a functioning network.
Alongside that, the peptide itself signals for collagen and glycosaminoglycan synthesis, and has a documented role in wound repair. This is the peptide with the strongest evidence base in the category.
What it cannot share a bottle with
This is the important part, and it catches almost everyone.
Vitamin C reduces copper, breaking the complex. Chelators — EDTA, phytate, gluconate — will strip the copper away, since stripping metal ions is precisely their job. That is why the copper serum in Plump It Up leaves the chelator out. Direct acids at low pH destabilize it. Strongly anionic ingredients precipitate it.
So a copper peptide serum is its own product. It does not go in the same bottle as your vitamin C, and it does not go in a formulation you have chelated hard for stability. If you want both, use them at different times of day.
- Never with: ascorbic acid, EDTA, strong direct acids, high-sulfate surfactants
- Fine with: hyaluronic acid, glycerin, panthenol, niacinamide, betaine
- Keep pH between 5.0 and 6.5
Working with it
Sold as a pure powder or as a 1% solution. The guides use the powder at 0.1%, dissolved in a spoonful of the batch water first; a 1% solution is used at 2 – 4%. Cool down, water phase, below 40 °C.
It will turn your serum blue. This is normal, it is not a sign of anything going wrong, and it fades slowly as the complex degrades — which makes color a rough freshness indicator. A copper peptide serum that has gone green or colorless is finished.
Refrigerate it, and make small batches. This is not an ingredient to buy in bulk and work through slowly.
Where it shows up in the guides
This ingredient appears in 1 of the formulations across the catalogue, at these rates:
| Guide | Formulations | Rate used |
|---|---|---|
| Plump It Up | 1 | 0.1% |
Keep reading
- Peptides, Part One: The Signal Peptides
- Peptides, Part Two: Argireline and Tripeptide-29
- Niacinamide
Every formulation in the guides gives you percentages, gram weights for a real batch, the method, the pH target and where to buy each ingredient.
See the guidesDuplika Beauty · duplikabeauty.co · This is formulation information, not medical advice. Patch test anything new.
