In 2012, a small team of chemists and architects in Córdoba, Spain, began asking a question that most of the paint industry considered irrelevant: what if a paint finish could actively improve the quality of the air around it? The result — Graphenstone — has since become one of the most credible stories in sustainable construction finishes, sold in over 40 countries and specified on projects ranging from private residences in Madrid to WELL-certified office buildings in London.
The core technology is relatively simple to describe: natural lime (calcium hydroxide) forms the binder, replacing the synthetic polymer binders used in conventional emulsion paints. To this, Graphenstone adds a small percentage of graphene — the world's thinnest and strongest material — which dramatically improves durability, flexibility, and adhesion without changing the paint's natural composition.
A paint that absorbs CO₂
Lime-based finishes have a natural carbonation process: as the paint cures on the wall, it reacts with atmospheric CO₂ and converts it into calcium carbonate (limestone), effectively sequestering carbon within the wall finish. Graphenstone estimates that one litre of their paint absorbs approximately 3.5kg of CO₂ over its lifetime — enough that a typical room repaint results in a net carbon-negative coating.
This is not a marketing claim. The carbonation chemistry is well-established and independently verifiable — it is the same process by which lime-mortared masonry gains strength over centuries. What Graphenstone has done is apply it to an interior finish that is commercially viable and aesthetically competitive with anything on the market.
"We did not set out to make a sustainable paint. We set out to make the best paint. The sustainability came from going back to the materials that nature had already perfected." — Pedro González, Graphenstone Founder
The full range: what to specify and when
Graphenstone's product line can be confusing at first glance — there are seven sub-ranges, each optimised for a different application. Here is our simplified guide:
- Ecosphere Premium — The core interior wall paint. Matt finish, 1,200+ colours available. Recommended for residential and commercial interiors. Coverage: 10–12m²/L. One coat typically sufficient over white primer.
- GrafClean Premium — For bathrooms and kitchens. Enhanced moisture resistance while retaining the lime-based formula. Satin finish option available.
- GrafStone Micro — A microcement-effect finish. Very popular with designers seeking a Venetian plaster look at a fraction of the cost and complexity.
- GrafSeal — Clear sealant for sealing existing lime plaster or exposed brick before painting. Essential for historic buildings.
- GrafExtreme — Exterior facade paint. High breathability (sd < 0.01m) prevents moisture trap behind render — critical for older masonry buildings in Spain's varied climate.
Keim: the German counterpart
No review of natural mineral paints in Europe would be complete without Keim. The German company, founded in 1878, invented the silicate paint system still in use today. Where Graphenstone uses lime as its binder, Keim uses potassium silicate — a liquid glass that forms an irreversible mineral bond with any siliceous substrate (concrete, plaster, brick, stone).
The result is a paint that does not peel, crack, or flake — ever. Properly applied on a compatible substrate, a Keim finish is rated for 30+ years exterior life. In Spain, it is distributed through keim.es and stocked by a number of specialist architectural paint retailers in Barcelona and Madrid.
For exterior facades on historic buildings in Spain — many of which have lime or sand-cement renders — Keim Granital or Keim Purkristalat are our first-choice specification. For interior work, Graphenstone's colour range and aesthetic versatility make it the stronger choice for most projects.
Verdict: which to specify?
If your project is in Spain and you want a natural finish with genuine carbon-negative credentials, Graphenstone Ecosphere Premium is one of the most straightforward specifications available. It ships from Spain, has an extensive colour library, and is available to architects through their professional programme with dedicated technical support.
For exterior facades on masonry — particularly in Spain's coastal climate where salt and humidity are factors — the Keim Granital silicate system has a durability track record that is simply unmatched by any other product on the market.
Affiliate disclosure: This article contains affiliate links to Graphenstone and Keim. Soul Materials only recommends products independently evaluated by our editorial team. Commissions support our work at no additional cost to you.
