During our late November Artist Roundtable, we discussed a comment an artist had made on social media, stating that, in her experience, sable brushes often outlast synthetics. While it seemed to me right away that this would not be the case (based on what we know about the materials involved), several other artists quickly echoed her sentiment. As such, I thought I should take a closer look at what was going on here.
Synthetic filaments, such as polyester (typically PBT or polybutylene terephthalate, a polyester thermoplastic commonly used for durable, solvent-resistant brush filaments) and nylon, resist chemical degradation, tolerate abrasion, and maintain physical integrity across typical studio conditions. Natural hair, like sable, is primarily composed of keratin, a cross-linked protein that is more vulnerable to high-pH swelling, oxidative damage, and cumulative mechanical wear. Yet, apparently, in many studios, sables appear to endure. Why would this be the case? I argue here that the most plausible reconciliation is behavioral. How tools are handled, what tasks they are assigned, and how they are cleaned can dominate the lifespan outcome as much as the underlying material.
Sable brushes are made of keratin fibers, typically sourced from weasel species. Each hair has overlapping cuticle scales that raise the hairâs surface energy and increase the effective contact area (so on a surface that already has a tendency to wet, liquids will spread more readily). Surface energy here refers to the energetic cost of creating surface area (the boundary where the material meets another phase, such as air or paint). In physics and chemistry, we find that systems tend to spontaneously move toward lower-energy states, which are more stable. If a system is âhigh energyâ, we understand it as more unstable, tense, or can describe it as a âstretchedâ state. If a system is âlow energyâ, we understand it as being more stable, relaxed, or can describe it as being in a âsettledâ state. Materials with high surface energy, like keratin, tend to âpreferâ contact with other substances, especially liquids, because doing so reduces the overall energy of the system.
When a liquid touches a solid, the arrangement that wins is the one with less total interfacial energy. (You can picture this as the liquidâs adhesion to the solid winning over its own cohesion, but the key is the energy drop.) When that energy drops, the liquid spreads into a film rather than beading.
Illustration of a droplet of water interacting with a high and low energy surface.
We can think of wetting as the system looking for a lower-energy arrangement. Air offers little adhesive interaction with the hair, so a hairâair plus paintâair setup sits higher on the energy landscape than one where paint makes good contact with the hair. When oil paint meets keratin, replacing some hairâair and paintâair interfaces with a hairâpaint interface can lower the total interfacial free energy. In that case, the system moves âdownhillâ to a more stable, lower-energy state, which is why the liquid spreads rather than beads.
While keratin is mechanically strong, it is also chemically sensitive. Itâs composed of long protein chains held together by peptide bonds, with additional disulfide bonds serving as tiny molecular bridges. These crosslinks contribute significantly to the hairâs strength, elasticity, and ability to spring back after being bent or pulled. However, this structure can be damaged by common studio conditions. Alkaline cleaners, like high-pH soaps and detergents, can make keratin fibers swell and denature (lose their natural structure and springâthe proteins unfold or misalign without necessarily being chopped into pieces), gradually weakening the hair. At the same time, oxidative stress can break down certain crosslinks that help give keratin its strength. In studios, relevant oxidants include peroxides formed during drying oil autoxidation and environmental ozone or UV. (Note: certain pigments may also catalyze oil paint film oxidation, but the oxidants themselves arise from the environment and the oil.)
Beyond chemistry, mechanical stress also plays a role. Each time the brush is wetted and then dried, it undergoes a swellingâshrinking cycle that gradually fatigues the structure. Add to this the abrasive effect of pigment particles, especially gritty or mineral-based ones, and the outer layer of the hair, the cuticle, can begin to develop tiny fractures. These microfractures degrade the smoothness and cohesion of the fiber surface, reducing the hairâs ability to spring back to shape. Over time, this leads to a visible loss of point fidelity (the brush no longer forms a fine tip) and reduced spring (the brush becomes floppy or splayed).
Synthetic brushes are commonly made from PBT (polybutylene terephthalate) or nylon, both of which are thermoplastic polymers. These filaments are smooth and often engineered with tapered or crimped shapes to improve flow and paint pickup. In contrast to keratin, these polymers have lower surface energy, which means they do not attract or hold onto liquids as strongly on their own. Manufacturers often compensate for this by tuning filament geometry and micro-texture (tapers, crimps, and controlled knot density) to improve wetting, pickup, and flow.
PBT absorbs very little water, giving it excellent dimensional stability and strong resistance to swelling or softening. It performs well with common studio solvents such as odorless mineral spirits (OMS) and alkyd mediums. Nylon, while slightly more hydrophilic (attracted to water), may absorb more moisture and temporarily swell under wet conditions, but it still holds up well under normal painting use.
Importantly, synthetic brushes can develop hooked tips if exposed to hot water or nearby heat sources. This is plastic deformation from heat and differs from engineered flagging, which is an intentional fiber tip split that aims to improve paint handling.
Mechanical failure modes do diverge in useful ways. In sable, abrasive pigments and rough grounds blunt the very fine natural tips. As cuticles fray and paint creeps into the heel (the part of the brush where the bristles meet the ferrule and paint tends to accumulate), spring decreases and splay increases. Sable sheds when the knot loosens after many swellingâdrying cycles. Synthetics are less prone to tip abrasion, but, again, can suffer from heat-induced plastic set, which shows up as a persistent hook. With careful temperature control, synthetics usually retain edge and spring well across many cycles.
With all of this said, under matched abuse, synthetics should prevail. If you immerse both hair types in compatible studio solvents, agitate with pigment on a toothy ground, and cycle cleaning repeatedly under controlled temperature, the difference should become apparent. (Note: It is not recommended to soak any brush for long periods, since prolonged solvent contact can soften ferrule adhesives.)
Still, despite these material and mechanical realities, many painters continue to report longer usable life from sable. I believe it is behavior that ultimately closes this gap. Cost, scarcity, and a sense of delicacy change how we act. Artists tend to load sable more lightly, target less resistant applications, scrub less, clean sooner, and often avoid hot water. Synthetics, by contrast, are routinely assigned to more aggressive tasks like blocking, scumbling, targeting more resistant paint applications, or underpainting on more abrasive surfaces, where application is often more forceful and cleanup, possibly more casual. The result is divergent duty cycles. Furthermore, it is important to note that a worn sable can still serve as a soft blender where edge acuity is less critical, prolonging its perceived usefulness, while a synthetic with a curled tip is quickly retired. Survivorship and role bias then favor sable in memory.
Cleaning rituals amplify perception. Sable often produces an audible squeak against glass once the boundary films thin. This is a friction signal at the surface, not a guarantee of complete oil removal throughout the tuft (entire bundle of bristles or filaments). Smooth PBT may not squeak even when equally clean. Heft and balance of premium handles can further bias judgments about control and longevity. These tactile and auditory cues shape perceived durability more than we notice.
Even brush wear patterns can reinforce this illusion. Sable tends to splay slowly and radially as the cuticle frays and spring fades, but the soft, uniform bloom still blends well and often remains in use for delicate passages. In contrast, synthetics may exhibit sudden failure in the form of hooked tips and/or significant splay, especially after heat exposure. The same amount of wear may appear more dramatic in synthetic brushes because it disrupts common function more visibly and abruptly. As a result, artists may retire synthetics sooner, while continuing to use worn sables for glazing or softening, even when both are comparably fatigued.
A sound care routine narrows the durability gap across hair types. If available, begin by massaging a small amount of painting oil or a compatible diluent into the bristles to lift hydrophobic paint films before introducing water and mild soap. This approach follows the conservation principle of removing like with like and minimizing early water exposure for natural hair. This approach also aligns with principles found in both Mayerâs The Artistâs Handbook and Gottsegenâs The Painterâs Handbook, which emphasize avoiding premature exposure to water, particularly with natural hair brushes, and caution against harsh soaps or over-wetting that can drive pigment into the ferrule. While neither author explicitly states that oil should be the first cleaning step, their focus on preserving brush elasticity and minimizing chemical stress supports the logic of removing oil-bound residues before emulsifying with soap and water. I also often recommend tying appropriately resilient brushes to maintain brush form and combat some of the influences that lead to splaying. If you are not familiar with the practice, tying is the delicate wrapping of bristles with damp cotton thread to assist in shaping and to combat splaying during drying.
Use cool or tepid water to avoid thermal set in synthetic filaments and to limit keratin swelling in natural hair. Never soak brushes in solvent, as prolonged contact can soften or dissolve the adhesive within the ferrule. Rinse until a pinch produces no foam. Some recommend blotting on a white, lint-free towel to check for tint or a greasy halo, though I often advise against this with wet brushes, as particulates can transfer and lodge in the tuft. After rinsing, carefully reshape the brush. Again, for appropriately resilient brushes, you can also consider tying.
Blended brushes, those combining natural and synthetic fibers, occupy a flexible space within the resistance spectrum, offering a hybrid of capillary finesse and structural resilience. Fluid handling considerations help explain why many of these blends excel. Even a small proportion of natural hair can increase capillary uptake and sustain continuous flow in thin passages. Engineered synthetic filaments contribute spring and recovery, preventing the tuft from collapsing under pressure. High-performing blends often use tapered and sometimes crimped PBT, combined with thoughtful knot density (the diameter and packing of the bristle bundle at the ferrule), so the tip behaves like sable while the heel resists splay and pigment movement into parts of the brush where itâs hard to remove and causes long-term structural problems. General performance, of course, varies with filament diameter, taper geometry, and overall tuft architecture.
To choose a brush set wisely (especially for oil) consider the resistance-based roles laid out in our Language of Painting curriculum. Brushes are best selected not only by name or material, but by how much mechanical resistance they offer when applied to the surface:
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High-resistance brushes (donât bend or give as easily) provide a strong counterforce and are excellent for reshaping, scumbling, and blocking in paint. Their rigidity allows for aggressive mark-making and movement of thicker paint layers. High-resistance brushes also serve as the basis for the analog brush dynamic promoted within my curriculum. High-resistance brushes may also be returned to at the end of a general painting process (as seen on our wheel) to gain an advantage in certain late-stage procedures.
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Medium-resistance brushes (often mid-stiff synthetics or firm blends) offer moderate pushback. These are ideal for general smoothing, more controlled blending, or gentle movement of surface paint without significantly disturbing the structure beneath, as a higher-resistance brush may.
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Low-resistance brushes (sable and soft synthetic-sable blends) produce minimal impact on the underlying layer. These are used for surface manipulation (removing texture or evening out sheen) and/or very subtle blending. They excel in final passes where surface manipulation matters more than underlying structure.
This procedural logic (bristle to synthetic to sable and back) forms what I call the Resistance Brush Wheel, a cyclical model that helps artists select tools in harmony with each stage of paint manipulation. A brushâs material matters, but its behavior in the hand is better predicted by resistance, which governs how it interacts with the viscosity and layering of oil paint.
With disciplined use and material/temperature-aware cleaning, synthetic and blended brushes can often outlast natural hair by a wide margin and offer excellent value for lifespan per dollar. Blends in particular can deliver the best of both worlds: sable-like flow at the tip and synthetic resilience at the heel, with a resistance profile that adapts well across painting stages.
Happy Painting!
