02/07/2026
Inaccurate Claims About Heat Bodied (Stand) Oil
Marketing claims are sometimes made by art materials manufacturers about products that are, at best, overstated or, worse, inaccurate. The text below is taken from a boutique manufacturer’s website about the differences between heat-bodied walnut oil versus linseed oil:
Heat Polymerized Walnut Oil or Linseed Oil ($18.50 for 80 mil. bottle) Heating (boiling, fuming) painting oils to burn-off their oxidative elements, concentrating adhesive power and toughening them, has been a practice for centuries. Dangerous to create, what I offer are the actual and truly heat-bodied oils as are found within the historical writings. The use of a heat-bodied oil typically promotes a leveling or melting condition to oil paint-- especially that fresh oil-and-pigment sort rubbed-up by the artist before use. Commercial tube paint containing Aluminum Stearate is not as much affected by stand oil and so many artists swear by its use, as it gives their paint a smoother more enamel-like appearance and tougher binding-power. That noted, instead of commercial stand oil, I recommend actual heat-bodied walnut and linseed oils for the very same purposes. Each of these processed oils has a thiiner consistency than standoil while yellowing only faintly when compared to common linseed oil. [Note: "sunning" oils to pre-polymerize and thicken them will not produce the detection earmarks of a true heat-bodied oil.
Overall, the claim that heat-bodied walnut oil is superior, or at least performs better, in painting than linseed oil is overstated. A heat-bodied oil is mainly chosen for handling and film characteristics, such as leveling, reduced brushmarks, gloss, and toughness. If you already accept those effects, then the practical reason to body walnut instead of linseed is mostly about color and paleness, not about fundamentally better performance.
Walnut oil is typically lighter in color and tends to yellow less than linseed, which is why it’s often preferred in whites, light tints, and cool mixtures. If you then body it, you can get stand-oil-like handling while keeping the base oil relatively pale. That’s the real “use case” where a heat-bodied walnut oil may make sense.
However, linseed has the advantage of overall film robustness, which is why “stand oil” in conservation/industrial contexts is typically defined as bodied linseed oil: it forms a tough, flexible, weather-resistant film while yellowing less than untreated linseed. In other words, if your priority is “best all-around drying oil film,” linseed remains the default.
Two additional practical points:
Walnut oil generally dries more slowly than linseed oil in artist use, and that tendency can remain once you body the oil—bodied oils already dry slower than raw/refined oils.
Yellowing differences between oils are real when comparing the oils alone, but the magnitude of the advantage depends heavily on conditions such as pigment-to-oil ratio, pigments, additives, and drying time. Long-term tests show that oil yellowing is complex and not always dramatically different across variables that people assume matter.
While some statements by the manufacturer align with what conservation science and coatings-industry practice say about bodied (heat-polymerized) drying oils, a few claims are inaccurate.
The biggest technical problem is the repeated claim that heating “burns off” or “fumes off” the oil’s oxidative elements, which is why the oil dries slowly. Drying oils don’t contain a separable “oxidative fraction” that you remove to make them bodied. In heat-polymerized oil manufacture, the oil is heated to high temperatures (typically ~300 °C) with oxygen largely excluded (under vacuum or an inert blanket such as nitrogen), so the triglycerides polymerize without first oxidizing. The resulting oil has a higher molecular weight, fewer readily reactive sites, and that’s why it tends to level well, form a tough film, yellow less, and dry more slowly than untreated linseed oil.
The statement: “This oil takes about a week to dry because its more oxidative elements have been fumed-off” is not a good explanation. Heat-bodied oils typically dry more slowly because of their altered chemistry (heat polymerization under low oxygen), not because something oxidative was removed.
On the process description, the claim that the maker’s oil is produced “without the CO₂ atmosphere and at a much higher temperature than commercial standoil” is at least suspect as a general statement. Heat-bodied oil is produced by heating linseed oil anaerobically to ~300 °C, with oxygen exclusion achieved via vacuum or an inert atmosphere. “Much higher temperature” than that is not typical for “stand oil” and can push toward thermal degradation/darkening rather than the properties artists usually want.
A few other points are directionally right but overstated or too absolute:
The statement that heat-bodied oils promote an “enamel-like” leveling/flow is broadly consistent with how stand oil is described (viscous, self-leveling, smooth films).
“Yellowing only faintly when compared to common linseed oil” is broadly consistent for stand oil vs. raw/refined linseed, and walnut oil in general tends to yellow less than linseed; but the exact yellowing depends heavily on the starting oil, refining, temperature/time profile, and exposure history, so it shouldn’t be presented as a guaranteed outcome for any one boutique process.
The discussion of aluminum stearate is in the right neighborhood (it is a common rheology/pigment-suspension additive and can affect paint body/handling), but “commercial tube paint containing aluminum stearate is not as much affected by stand oil” is not a reliable generalization. Aluminum stearate can already gel/structure the oil phase, so the perceived change from adding stand oil may be smaller in some paints, but it’s formulation-dependent; aluminum stearate is also implicated in other behaviors of modern paints that have nothing to do with stand oil “not working.”
The aside that sun-thickened oils won’t show the same “earmarks” as true heat-bodied oil is basically reasonable in concept: sun-thickening involves oxidation as well as polymerization and is often described as drying faster than stand oil, whereas stand oil is made under oxygen-excluded conditions. The phrasing is just vague.
I hope this explanation clarifies the differences between heat-bodied walnut and linseed oils.
