José Manuel Torralba, IMDEA MATERIALS

From the legendary Toledo steel swords to the biomaterials that today help regenerate bone, or the catalysts that are transforming the chemical industry, materials have been one of the keys to technological and scientific progress. In this field, Spain has contributed innovations that have left their mark on the world and form an essential part of our scientific history.

Toledo steel

Today, we know how Toledo swords were made and why, for centuries, they were considered among the best swords on this side of the world (in competition with Damascus swords and Japanese katanas).

They owe their properties to a sandwich-like structure: two layers of steel with a certain carbon content, allowing for very hard and easily sharpened edges, with an iron core.

The three layers were forged together and then quenched to give surface hardness. It must have taken many decades, perhaps centuries, to achieve the perfection of a sword that was hard on the outside but ductile on the inside, capable of cutting heads far better than any other.

Toledo swords underwent five quality tests to measure their hardness, toughness, and cutting ability. Many other swords passed three or four, but never all five. The final test, known as “the knee test”, consisted of bending the sword over a fixed support (often the knee), from hilt to tip.

These properties are related to their microstructure: by forging two steels of different compositions simultaneously, diffusion welding can be achieved in a single piece.

However, at the time, this could only be achieved by diffusing carbon into iron at high temperatures. The result depended on time, temperature, and other factors that were difficult to control.

The same was true of quenching: changing the temperature or the cooling medium, water, oil, or others, could completely alter the material’s properties. With so many variables at play, producing a perfect sword was almost a miracle.

Spanish porcelain

Ceramics are among the first materials ever produced by humans. One of the oldest known pieces is a small Venus figurine made in Věstonice (present-day Czech Republic) between 29,000 and 25,000 BC.

Since the Paleolithic, people discovered that certain sands could be mixed with water, shaped, and then “fired” in a kiln. However, there is one country where the quality and properties of ceramics advanced much faster than elsewhere: China. There, between the 1st and 2nd centuries, porcelain emerged—very dense, highly resistant, and sometimes almost transparent.

Once this ceramic crossed borders, it became an obsession for Japanese, Korean, and European artisans. However, uncovering its secrets took Europeans many centuries.

Some secrets were related to the composition of the clay and others to its processing. Today, we know that the key ingredient is a white clay called kaolin.

This interest in unlocking the secrets of porcelain also reached Spain. In the 18th century, within the reformist spirit of the Enlightenment, initiatives emerged to develop a ceramic industry capable of competing with other European centres. One of the most ambitious projects was the Royal Factory of Earthenware and Porcelain of L’Alcora, founded in 1727.

Although it initially produced mainly fine earthenware inspired by French and Italian models, the factory quickly became a true laboratory of innovation and technical experimentation. Beyond its artistic value, it had a notable technological impact. Many of the artisans trained there later spread knowledge and techniques to other ceramic centres, helping to modernise production in different regions.

Thus, L’Alcora not only produced high-quality pieces, but also helped consolidate a more advanced ceramic tradition. One consequence was the founding in Madrid, in 1760, of the Royal Porcelain Factory of Buen Retiro (known as “La China”), promoted by Charles III, who also brought master ceramists from Naples. Its reputation became so important that it rivalled French porcelain from Sèvres and posed serious competition to English porcelain.

Perhaps for this reason, during the Peninsular War, in August 1812, British “allies”, specifically General Rowland Hill, took advantage of their victory over the French at the Battle of Retiro to blow up the factory and reduce it to ruins.

Bioceramics the regenerate bone

In recent years, Spain has contributed materials that are transforming medicine, energy, and industry. A clear example is bioceramics for bone and tissue regeneration.

These materials are designed to interact with the body and promote bone regeneration in complex fractures, dental implants, or diseases such as osteoporosis. Unlike conventional metals or polymers, they do not simply act as support, but actively stimulate the formation of new tissue, becoming key elements in regenerative medicine.

The research group led by Professor Vallet-Regí at the Complutense University of Madrid is a pioneer in the use of bioactive glasses and ceramics capable of integrating with bone and releasing ions or drugs in a controlled manner. Internationally recognised, her work has placed Spain at the forefront of biomaterials, with advances that improve the quality of life of millions of people.

Zeolites for the energy industry

Another example is the zeolites developed at the Institute of Chemical Technology (ITQ, UPV-CSIC) by the team led by Dr Avelino Corma, which have placed Spain among the global leaders in catalysis.

These are microporous materials that act as “molecular sieves”, capable of filtering, separating, and accelerating chemical reactions with great efficiency.

Their impact has been enormous in the chemical and energy industries, where they are used in oil refining, the production of cleaner fuels, and the synthesis of compounds used in plastics, fertilisers, and medicines. Thanks to their stability and selectivity, they have enabled more sustainable and cost-effective processes on a global scale.

At the same time, Spanish research centres are now working on graphene, perovskites, and many other materials that could shape the next technological revolution.

Spain, therefore, has not only had a brilliant past in the art of materials, but continues to play a leading role in creating innovations with global impact.

José Manuel Torralba, Full Professor at the Carlos III University of Madrid, IMDEA MATERIALS

This article was originally published in The Conversation. Read the original (content in Spanish).