For centuries, every art student has learned the same rule:

Oil and water do not mix.

Yet today you can buy oil paints that thin with water, clean up with water and often don't require solvents at all.

So what changed?

Have chemists somehow broken the rules of painting?

Not quite.

Water-mixable oils are one of the most significant developments in artists' materials of the last fifty years. They solve many of the practical problems that have made traditional oils difficult to teach in schools, while still retaining many of the qualities artists love about oil paint.

For teachers, understanding how they work can help answer an important question:

Are water-mixable oils simply a compromise, or are they a genuine alternative for GCSE and A-Level art?

Despite its importance in the history of art, oil painting has often been difficult to accommodate within school environments.

The challenges rarely come from the paint itself. Instead, they arise from everything surrounding its use. Traditional oils typically require solvents for thinning paint, cleaning brushes and preparing surfaces. This introduces considerations around storage, ventilation, health and safety procedures, and classroom management.

For many departments, particularly those working within tight budgets and limited teaching spaces, these practical concerns can make oils feel more trouble than they are worth.

As a result, students frequently encounter oil painting only through reproductions of famous artworks rather than through direct experience of the material itself.

That is a shame because oils offer something unique. The ability to blend colours over extended periods, build complex layers and manipulate surfaces slowly encourages a different pace of thinking and making than many contemporary classroom materials.

To understand why water-mixable oils are unusual, it helps to understand why oil and water normally avoid each other in the first place.

Water molecules are what scientists describe as polar. They are attracted to other water molecules and readily form bonds with them. Oils, by contrast, are non-polar. They prefer to bond with other oils.

This difference means that oil and water naturally separate into distinct layers rather than combining into a stable mixture.

The same principle applies in traditional oil paint. Pigments are suspended within drying oils, usually linseed oil, which actively resists mixing with water. That is why artists have historically relied on solvents such as turpentine or white spirit when they want to alter consistency or clean brushes.

For centuries, this was simply accepted as part of oil painting.

The answer lies in some surprisingly clever chemistry. Rather than changing oil paint completely, manufacturers modify the oil binder itself so that it can interact with water while still retaining the characteristics that make oil paint unique. In simple terms, part of the oil molecule is adapted to attract water, while the rest continues to behave like a traditional drying oil.

You can think of it as creating a bridge between two normally incompatible materials. One part of the molecule is comfortable in an oily environment, while another can interact with water. This allows water to disperse through the paint during mixing and cleaning, even though the paint itself remains fundamentally oil-based.

A useful comparison is mayonnaise. Although mayonnaise contains both oil and water, the two do not separate because an emulsifier helps them coexist. Water-mixable oils work on a similar principle. The chemistry is very different, but the outcome is comparable: two substances that would normally repel each other can temporarily work together.

The important point for teachers is that water-mixable oils are still oil paints. They retain the blending qualities, colour richness and slower drying times associated with traditional oils, but without requiring solvents for thinning and brush cleaning. That combination is what makes them particularly attractive for educational settings.

Students often assume that water-mixable oils are simply acrylic paints in disguise.

They are not.

Although both can be used with water, they dry in completely different ways. Acrylic paint dries primarily through the evaporation of water. Once dry, the paint film becomes permanent and cannot be reworked in the same way.

Oil paints dry through oxidation. Rather than water leaving the paint, oxygen from the air reacts with the oil binder, causing it to harden gradually over time.

This slower process gives artists longer working times and greater opportunities for blending, soft transitions and subtle colour mixing. It is one reason why so many painters continue to value oils despite the popularity of acrylics.

For students exploring painting media at GCSE or A-Level, comparing the two processes can lead to useful discussions about how materials influence artistic outcomes.

Introducing water-mixable oils is not simply about teaching a new product. It is an opportunity to deepen students' understanding of materials and artistic decision-making.

Students quickly begin to recognise that different paints encourage different approaches. Acrylics often reward speed and decisiveness. Oils encourage observation, adjustment and refinement.

Because water-mixable oils remain workable for longer, students can spend more time blending skin tones, adjusting colour relationships and developing subtle transitions. This often supports observational painting projects where gradual development is more important than immediate results.

The material also creates opportunities for cross-curricular learning. Discussions around chemistry, material science and innovation sit naturally alongside practical painting activities.

Rembrandt

Rembrandt remains a useful reference when introducing students to the qualities that made oil paint dominant for centuries. His glazing techniques, rich shadows and subtle colour transitions demonstrate how oil paint can create depth and atmosphere in ways that continue to influence artists today.

Source: The Man with the Golden Helmet, c.1650, Circle of Rembrandt, Gemäldegalerie, Berlin (Public Domain).

Kehinde Wiley

Wiley's large-scale portraits combine the techniques and visual language of Old Master painting with contemporary subjects. His work provides a powerful discussion point around representation, power and who gets included in art history. Students can also analyse his use of colour, pattern and highly finished oil painting techniques.

Source: Kehinde Wiley, Barack Obama (2018), Smithsonian National Portrait Gallery, Washington, D.C.

Source: Kehinde Wiley, Equestrian Portrait of Philip IV (2009).

Catherine MacDiarmid

MacDiarmid is a contemporary painter known for using water-mixable oil paints extensively in her landscape work. Her paintings demonstrate that artists do not have to compromise on colour, atmosphere or professional quality when choosing water-mixable oils.

Source: Catherine MacDiarmid, Portrait Portfolio, Catherine MacDiarmid Artist. Available at: catherinemacdiarmid.co.uk

For many departments, the most obvious benefit of water-mixable oils is practicality.

Brushes can often be cleaned using soap and water rather than specialist solvents. Classrooms experience fewer strong odours. Storage requirements become simpler and setup and clear-up times are often reduced.

This does not mean health and safety considerations disappear entirely. Good studio habits remain important. However, many of the barriers that have traditionally discouraged schools from introducing oil painting become significantly easier to manage.

Perhaps most importantly, teachers gain access to the educational benefits of oil painting without introducing the same level of complexity into everyday classroom routines.

Traditional oils still have an important place within art education, particularly when students are exploring professional studio practice or specialist painting techniques.

However, water-mixable oils provide an accessible route into the medium for many schools. They allow students to experience the unique handling qualities of oil paint while reducing many of the practical challenges associated with traditional methods.

The goal is not necessarily to replace traditional oils entirely. Instead, it is to make the educational benefits of oil painting available to a wider range of students and learning environments.

For departments balancing curriculum ambition with practical realities, that can be a valuable compromise.

·       Water-mixable oils remain genuine oil paints rather than modified acrylics.

·       They dry through oxidation, just like traditional oils.

·       Students can explore blending, layering and colour mixing techniques associated with oil painting.

·       Reduced reliance on solvents can simplify classroom management and cleaning routines.

·       The material creates opportunities to discuss science, innovation and artistic process alongside practical painting skills.

If you've never introduced oil painting because of concerns around solvents, storage or classroom management, water-mixable oils may be worth another look. They provide many of the qualities that make oil paint such a rewarding medium, while fitting more comfortably into the realities of today's art room.

For many teachers, they could be the difference between talking about oil painting and actually teaching it.