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Linseed paint

Linseed paint Posted on 12 June 2024

Mixing linseed oil paint

Michiel Brouns has rejuvenated the interest in traditional painting techniques through his linseed oil based products.  

Twenty years ago, I entered leading restoration expert Haske van Zadelhoff’s shop in Gulpen, Netherlands, marking the start of my love for historic buildings. Gulpen, in Limburg, had a distinct architectural vibe, similar to Fachwerk houses in Germany and Belgium. Haske became my mentor, guiding me through moisture dynamics and the use of materials such as lime plaster, lime washes and clay to revive structures.

I somehow convinced Haske to bring me on board, bidding farewell to my corporate stint. Over the next three years, he imparted invaluable knowledge about moisture in ancient structures and the transformative power of materials like lime plaster and clay. Amid this wealth of information, one product stood out and captured my fascination: linseed oil paint. It surprised me that hardly anyone chose this non-film forming finish, opting instead for conventional plastic paints on timber.

This curiosity fuelled my personal research journey into wood treatments, aiming to uncover not only the most historically accurate methods, but also those most beneficial for the structural integrity of historic fabric. A pivotal question emerged: why were centuries-old buildings, which had endured without any issues, suddenly succumbing to crumbling plaster and rotting timber? The answer lay in the introduction of man-made, petrochemical paints and wood treatments in the 1930s – a wave accelerated by the post-war boom in plastic-based resources like acrylics, latex, and alkyds.

The rebuilding of war-torn Europe witnessed the dominance of plastic paints, along with the widespread use of concrete, Portland cement, steel and structural glazing, replacing traditional materials. Fortunately, some regions, including southern Sweden, Germany, Denmark, northern England, and Northern Ireland, clung to traditional materials like linseed oil paint. Despite their role in preserving linseed paint, these areas experienced a significant loss of knowledge. Over the last two decades, I delved into historical texts, accumulating more than 50 volumes detailing not only the traditional production of linseed oil paint but also its application.

The dwindling knowledge and production of linseed paint propelled me to embark on its production, driven by a desire to contribute to the preservation of cherished buildings. My vision was to create a high-quality linseed oil paint on a commercial scale, breaking away from its exclusivity to a handful of specialists. This paint should be accessible for use on both historic timber and contemporary structures. In tandem, I sought to share as much information as possible about linseed paint, prompting me to regularly deliver ‘Demystifying Linseed Paint’ presentations to architects and building industry professionals.

Readers of Decorating Matters are likely acquainted with linseed oil, linseed paint, or linseed varnish, understanding the importance of high-quality ingredients. Let me take you back to the inception of my production process, rooted in the quest for the highest-quality linseed oil.

Linseed oil, derived from pressing flax seeds (Linum usitatissimum), underscores the versatility of the flax plant, where different parts serve varied purposes. The tall variety is utilised for linen production, while the shorter variety yields linseed oil. Optimal linseed oil quality is achieved through cold pressing, but large-scale industrial production often resorts to hot pressing or chemical additives for higher oil yield, resulting in a low-grade oil unsuitable for quality paint. Impurities in linseed oil increase the risk of premature degradation in the finished paint product.

Rather than importing high-quality oil from Sweden or Denmark, my company chose the north of England, rich in flax-growing conditions and with a historical legacy in flax cultivation. A local farmer already produced top-tier linseed oil, selling it under the name of flax oil for equestrian use. The food-grade standard of their oil, achieved through meticulous filtration rather than chemical washing, provided an ideal starting point for our linseed paint production.

Boiling raw linseed oil, classified as a drying oil, is imperative for enhancing its drying capabilities and serving as a carrier for pigments. Contrary to common belief, boiling isn’t primarily to remove moisture; it’s a method of transforming raw oil into boiled oil. Our boiling process, done in an actual boiler, underwent refinement through trial and error due to a scarcity of descriptions of the old methods, tools and temperatures. The consistency and quality of raw linseed oil can vary from harvest to harvest, necessitating continual tweaking of the boiling process.

Linseed oil, whether raw or boiled, lacks adequate protection against UV breakdown when used outdoors. The aggressive nature of sunlight in exterior settings prompted our forefathers to mix earth into the oil, enhancing wood treatment durability. Traditionally, pigments were incorporated into oil using a muller and slab, a method continued by artists for centuries. The Industrial Revolution introduced steam-driven triple-roller mills, replacing the muller and slab technique, allowing larger-scale production. In our factory, we still employ these triple-roller mills, although no longer steam-operated.

In the art world, linseed paint incorporates myriad pigments, from raw earth pigments to animal and vegetable pigments. Industrialisation introduced metal-based pigments and those derived from industrial processes. While most pigments work well in a water-based medium, not all disperse well in linseed oil. Hence, we work with a specific number of pigments to create pastes, ensuring the correct colour mix while preserving historical accuracy in texture and feel.

Despite historical use, certain pigments have fallen out of favour, with lead white being a prime example. The adverse health effects of lead were known in the Middle Ages, yet its use persisted until the early 1900s in Europe. The development of zinc and titanium provided safer alternatives, offering 90 per cent of the efficacy of lead white without health hazards. We incorporate
zinc white into our linseed paint for its natural anti-mould properties.

The health hazards associated with plastics extend beyond personal wellbeing to the environmental realm. Modern paints, essentially coloured liquid plastics, contribute significantly to plastic waste. A study by EA reveals that 58 per cent of all ocean microplastics originate from paint, with the majority coming from domestic use. Shifting back to time-tested materials such as lime wash, clay paint, and linseed oil paint, made from raw earth ingredients, aligns with a circular, cradle-to-cradle philosophy. Unfortunately, commercial exploitation hampers this approach, with cradle-to-cradle certification demanding hefty fees, undermining its essence.

The building industry has an opportunity to draw vital lessons from our forefathers, incorporating their knowledge into solutions for contemporary environmental challenges. Embracing historic building materials such as linseed paint and lime washes isn’t merely an ode to authenticity but actually a step towards sustainability, with a significantly lower carbon footprint compared to synthetic materials. As we navigate the future, a return to these time-honoured practices could be a beacon guiding us towards a more sustainable built environment.  

To buy Michiel’s book see