Why Is Copper Peptide Serum Blue?

Copper peptide serum is blue because GHK-Cu is a copper complex, and copper(II) complexes absorb light in a way that makes them look blue. The colour comes from the ingredient itself. It is not a dye and it is not a sign of strength.

Why is copper peptide serum blue?

GHK-Cu is a small peptide (glycyl-histidyl-lysine) holding a copper ion. When copper is bound in this way, it absorbs some of the orange and red part of visible light, so the solution that is left looks blue. That is ordinary colour chemistry, the same reason many copper compounds in a lab are blue or blue-green.

Chemists have studied this complex in detail. A 2001 study in Biochimica et Biophysica Acta used UV-visible spectroscopy, among other methods, to map how GHK binds copper [1], and a 2012 study in the Journal of Biological Inorganic Chemistry measured how tightly it holds it: about as tightly as the copper-carrying site on albumin, the main protein in blood [2].

Does a deeper blue mean the serum is stronger?

No. Depth of colour depends on how much copper complex is in the bottle, but also on the rest of the formula, how it was made and how the light hits it. You cannot read potency or results from a shade. The percentage on the label is the better thing to compare.

Why are some copper peptide serums not blue at all?

A serum can look clear, pale or tinted for several reasons: a lower amount of the copper complex, a different type of copper peptide, or a formula built around other peptides with only a trace of copper. Colour alone will not tell you which. Check the ingredient list for GHK-Cu or copper tripeptide-1 and the stated percentage.

Is the blue colour safe for skin and clothes?

The tint is part of the ingredient, so it is expected. As with any skincare product, patch test first, and keep serums off light fabrics until they have absorbed. If your skin reacts, stop using the product.

What does GHK-Cu do in skincare?

In research contexts GHK-Cu has been studied for its role in how skin cells signal and make structural proteins. In skincare it is used to support the look of firmer, smoother skin. Results vary from person to person and take consistent use over weeks.

Where to start with koppā

The High Potency GHK-Cu 2% Serum is koppā's copper peptide serum. Its blue colour is the natural colour of the GHK-Cu complex. For the wider routine questions, see the FAQ.

Sources

1. Conato C, Gavioli R, Guerrini R, et al. Copper complexes of glycyl-histidyl-lysine and two of its synthetic analogues: chemical behaviour and biological activity. Biochimica et Biophysica Acta. 2001;1526(2):199-210. Read the paper
2. Trapaidze A, Hureau C, Bal W, Winterhalter M, Faller P. Thermodynamic study of Cu2+ binding to the DAHK and GHK peptides by isothermal titration calorimetry (ITC) with the weaker competitor glycine. Journal of Biological Inorganic Chemistry. 2012;17(1):37-47. Read the paper

For the full research on GHK-Cu, see our complete guide to GHK-Cu.