Making Paint: Machine Milled vs. Hand Mulled Paint

Paint is more than just a simple mixture. In order for pigment to become paint, it has to be dispersed thoroughly in a vehicle, and that takes skill, time, and work. That work can be either done by hand or by machine, but which method yields the best result?

Image (left): Utrecht Art Supplies Brooklyn paint milling facility, mid-20th century

Many of the most celebrated artists of the past used paint that was made by hand with a glass or stone tool called a muller. From the beautiful, well-preserved appearance of important Baroque and Renaissance paintings, it’s easy to think hand-mulled paint is superior to what’s available today, but in terms of raw materials and how well they’re prepared, modern, manufactured paint has important advantages over small-batch paint of the past.

It takes physical force to combine pigment and vehicle, and in the past, that might have started with a mortar and pestle reducing bulk materials to powder, and maybe even picking out impurities, before using a muller to disperse the pigment in oil. Today, most modern pigments are supplied in a very fine powdered form from the source, already reduced to tiny particles, however it still has a lot of clusters and clumps that need to be broken apart. Instead of a muller, this work is now done using a Three Roller Mill, a powerful, high speed machine.

A paint mill generates many more revolutions than a hand-powered muller, much faster than a human hand. Colors may pass through the mill several times until it achieves the perfect dispersion, with each pigment particle coated. Internal water cooling ensures that the rollers will not overheat the paint.

Image (right): Freshly made oil paint emerging from the mill

The purpose of both mill and muller is to produce a fine, smooth mixture with each discrete particle coated in an envelope of vehicle. Using a hand muller, the artisan can only generate a few dozen revolutions per minute at most, so it takes a long time and considerable physical effort to make a small amount of paint.

Even the most thorough hand mulling can still leave undispersed pigment clusters, and though they may be smaller than the eye can see, every cluster represents some amount of pigment that isn’t being used to its best advantage.

Image (left): Left- Undispersed pigment clusters. Right - Fully dispersed, discrete particles of pigment.

That’s not to say that hand-dispersed paint is without advantages. Hand-mulled oil paint is developed slowly, giving the artisan a great deal of control over stiffness and pigment concentration. This type of paint typically uses plenty of pigment in premium quality vehicles, like walnut oil and cold-pressed linseed oil, bringing them closer in formulation to historical, "old master" paints. And, like historical paint, hand-mulled oil colors exhibit the unique properties of each pigment, like natural ropiness, a wide range of drying rates, and granularity.

However, not all artists enjoy their paint in the natural state. Through machine milling and laboratory controls, amendments can be added to manufactured colors to adjust drying rate and paint body, and to ensure stability. This way, it’s possible to offer an entire color assortment that dries within a reasonable amount of time, with each color responding correctly to the brush and palette knife. Stabilizers added during the milling process minimize separation and shedding of vehicle to maintain a homogeneous dispersion in the tube with minimal separation.

Image (left): Burnt Sienna at each of three millings

Hand-mulled paint provides a unique experience using excellent raw materials, but machine milling makes efficient, good use of every speck of color. Modern paint manufacturing also realizes economies of scale that make high-quality paint much more affordable and widely available than if it had to be made by hand, in a dazzling range of colors that would be the envy of any Old Master.

Image (right): Detail, Self-portrait by Alexander Roslin, 1790