Traditionally, artists and decorators made their own paint by mixing a paste from their chosen pigments and an oil base. They would do this by using simple, manual tools: just a muller (a short-handled tool for grinding pigments) and a slab. They would start by grinding the powder pigments with a little bit of oil, then would add more oil as they went to create the correct consistency. Artists would typically use less oil in their paint, while house painters would use more in order to create a thinner paint more suited for painting over large areas.
This traditional method of mixing by hand was not only time-consuming and labour intensive, but it was also quite difficult to produce a consistent result each time. To ensure the durability of the paint, it’s essential for the linseed oil and the pigments to be fully amalgamated with each other. If the paint isn’t properly mixed, it will go matte far more quickly, which will increase the requirements for maintenance.
In order to achieve the best results, the Brouns & Co manufacturing process uses column mixers and big barrels. The paint that is mixed in these barrels is then transferred to a triple roller mill. Here, the paint, which has more of a paste consistency at this stage, will pass through the rollers between three and five times, depending on the grain size of the pigments used. This process creates a beautifully homogenous consistency, which forms the basis for the eventual paint colours.
It’s important to note, however, that the mixture needs to stay close to room temperature. The friction of metal on metal generates considerable heat, and if the oil gets too hot it will get thinner, which makes it more difficult for the pigment to tack to. This means that the milling process has to involve additional measures to keep the oil and paste at the right temperature. This is achieved by using rollers that have a constant flow of cool water inside them.
Setting aside the modern machines and additional cooling techniques, in principle the method we use today of grinding pigment into boiled oil is hundreds of years old. With this in mind, you can begin to understand why linseed paint is more expensive to produce than the simpler methods used to produce modern plastic paint. However much of the difference in cost is offset by the excellent coverage rate of linseed paint, with a litre of linseed paint going a lot further than modern plastic paint.