Heat-Bodied Drying Walnut oil 2 oz bottle .........$30.00 US

A unique substance that is simply walnut oil altered through a complex heating. This Heat-Bodied Oil behaves in a different manner to other heat-bodied oils. Just about every heat-bodied oil known causes paint to levelize and exhibit dragging and "melting" of the handground paint. By contrast, one drop of this unique HB-Oil added to handground paint causes thixotropy-- the paint becomes "short" in texture-- as if a strong resin had been added to it. Here is a photo showing creamy-ground lead white (left) and what happens to it (right) when a couple of drops of the HB Oil are mixed in. The paint suddenly stands up and can be sculpted easily with the brush.

I can find no historical formula for this oil. If it was used by the olden painters, they left nothing beyond their works to clue me in. The use of this oil causes a certain brushwork that is oddly wonderful. It suits painters who desire heavy brushwork and who are not very careful about cleaning their brushes. Yet, it also allows a refined and charming textured paint quality with soft brushes.

During the mid-1700's, upon examining some of Rembrandt's comparatively fresh paintings, Joshua Reynolds came to the conclusion the older painter must have used wax and/or resins to achieve his interesting brushwork. Some today speculate Rembrandt's strange brush-topography was merely Stack Lead Carbonate ground with Linseed and some chalk. Of course, 100 years later and across the Channel, Sir Joshua was using the very same Lead White paint R had used. Doubtless it might often also have been adulterated with chalk. Apparently, Reynolds was not able to achieve Rembrandt's brushwork impasto by such mere means. Thus he declared something else had been used with R's Lead White and other paint.

Time has passed and, today, Modern Science tells us it cannot detect wax or resins within R's paint. This is very curious.... As in the case with the Getty Museum's micro-detective work performed on the Gentileschi works, I do wonder if any "highly" fluorescing paint has been found in R's paint chips, as this might indeed offer something in the way of clues to resin use. That aside, Science HAS declared there is a "heat-bodied oil" found in some of R's paint (meaning, I assume, the oil used by Rembrandt was at least boiled to a somewhat thickened state).

Elsewhere, I have speculated when a resin is highly-cooked into an oil, that resin is no longer itself and cannot be identified against its once pure chemical "footprint". However, regardless what becomes of that resin during the great heating, the oil constituent will doubtless test out as a heat-bodied oil. What I am saying here is perhaps many of these findings of heat-bodied oils are actually oil and resin varnishes rather than mere oil alone. But maybe not .... Certainly some faintly "heat-bodied" oils were simply made by cooking Lead oxides into the oil, thus to make drying oils. But do drying oils alone recreate the brushwork of Rembrandt? I would hazzard Joshua Reynolds would say "No" (he and his painting brethren used such leaded drying oils on a regular basis).

I wish to comment, a skilled painter assigned to copy Rembrandt's impasto can achieve a certain degree of success with some fresh oil, some simple lead carbonate, and some stiff round hog-brushes (owing to the appearance in his rugged impasto, I sincerely believe R's habits over brush-cleaning were lax). However, to get all of R's brushwork, something else --likely something thixotropic--does seem necessary. And so I agree with Joshua Reynolds, who certainly must have made his own copy-attempts and found need of something thixotropic to add to the equation. If there was no actual use of a resinous oil varnish involved-- as the conservators proclaim-- then I can find only one "heat-bodied oil" that produces the odd rugged impastoed effects of Rembrandt. Thus, I make and offer the HB Oil to the hand-grinding oil painting realm.

[Update, September, 2001: see the descriptive report on "16th Century Amber Varnish" (on the "Mediums" page) for an insightful modern day experiment showing the difficulty in detecting high-temperature resin-in-oil varnishes. It would now appear the high temperatures necessary to cause a resin to be fully incorporated into an oil do effectively destroy that resin's "markers", leading to a finding of only "heat-bodied oil" instead.]


In practice, the handground paint is first rubbed up to a heavy or light creamy consistency using raw Linseed, or, for greater ease in brushing, a good un-refined Walnut oil. The addition of one drop of this HB-Oil causes the paint to stand up in a short manner and stay put where placed. While applying, the paint builds easily upon itself -- even though wet. Very interesting texture and brushwork is attained. The resulting character is very similar in some ways as to having added much wax to the paint, though there is no wax or other additives within the HB-Oil. The unique and charming physical appearance of the final paint is unlike any produced through other agents-- including resins and oil varnishes.

The following 24x30 work entitled "Wind Before the Storm" was painted entirely with handground paint with a drop or two of HBO added. It is a rather textured work; for instance, the leaves of the forground trees are quite sculpted in texture; providing a physical quality and aiding the optical illusion of 3-D reality.

Note, the effect obtained from this HB-Oil is compounded with the use of modern tube colors which already contain a gelling substance (such as Aluminum Stearate). This HB-Oil is meant for handground paint, or a commercially made tube paint that only contains oil and pigment without stabilizers. Typically, this is indicated by a separation of oil and pigment observed upon opening the paint for inspection. This separation is harmless and occurs as a normal result of non-use of stabilizers-- like AS-- within the paint. Such pre-ground and slumping oil paint is simply squeezed out on the palette, a bit of preferred oil is added and the whole mixed to a proper creamy consistency before adding the drop of HB-Oil. For those who might wish to add the HB-Oil to their modern tube colors, such paint, if it is stiff, must first be re-ground to a creamy consistency using some chosen raw oil before adding the HB-Oil. [Do not fear adding some oil to stiff tube paint. Many experts today decry adding oil to commercial tube paint. There is some good and bad in this advice and it does not apply to all methods, nor all commercial tube paints, nor all oils; be aware, the olden works were painted with a judicious amount of oil. Those who handgrind their colors will know the proper amount of oil necessary. Repeating here, and as historically maintained, the paint is commonly rubbed up to a heavy-cream consistency, then tempered with a certain desired agent, giving the paint the proper character desired. ]

As with modern tube paint, brushwork dicroism results from thixotropic stabilizers-- like Aluminum Stearate. Use of the HB-Oil with handground paint will, of course, allow similar dicroism effects. For instance, in painting clearly graduated skies or broad flat areas, incidental reflective light will often cause optical dicroism. This harmless reflective light-effect, where one stroke of a color appears lighter or darker to other strokes of the same color, will result from strokes of paint not applied in the same general direction. Thus, it is better often to leave this HB-Oil additive out of paint meant for such smooth surface-desired areas, ( another of several routes would be to use a palette knife to trowel or "plaster" the surface down to a smooth condition free of hatching marks left by the brush-hairs). Dicroism is more noticeable on very smooth grounds. Of course, those desiring a painterly impasto-ish manner will not see such dicroism as a problem.

Use of the HB-Oil with handground paint will allow a resin-free technique while still obtaining most of the extra benefits such resin-use would have allowed. Paint is made by mixing the pigment up with raw oil or aged oil and pigment (aged walnut oil was a highly-prized item among painters).

This is the historical method: pigments were first crushed in a mortar with a pestle. This produced a pulverized powder but it was not nearly fine enough for pigment-use. For that degree of fineness, a muller and slab had to be utilized and some form of liquid lubricant was necessary. The liquids kept dust down and allowed a slurry to quickly form, aiding the mechanics of the tools. Such liquids were water and alcohol. One historian, Eastlake, surmised essential oil of turpentine being Rubens' choice for the chore (I'd question that). After and between color-grinds, Alcohol and water were easily cleaned from the muller and slab. Contrary to popular belief, I can find no 1600's or previous reference to the use of oil during the mulling stage.

After this secondary operation with muller and slab, the micro-ground pigments were dried and stored for use. At that needed time, the painter simply rubbed them up in small usuable amounts with raw oil and the knife to make the basic oil-and-pigment paint. Again, the muller and slab were not used and would represent an un-necessary waste of time and materiale. Also realize, once mulled to pigment-grade fineness, the dried substance that resulted from this secondary treatment (mulling) could be now too easily made hazardously airborne. You see, if the muller and slab were now brought back into action, the extreme fineness of the now dry micro-pulverized pigments would engender a breathable fume to spread throughout the studio. Know that this fuming is kept relatively modest by the knife-work. The small amounts of fresh paint can be rubbed up with a modicum of cautionary action.

[ There are those experts today who preach the use of the muller and slab for actual oil paint-making instead of the knife. Again, this is erroneous. This notion likely comes from the time-span of 18th and 19th century colormakers using such devices to work up large amounts of oil paint for storage into bladders and tubes to be sold. Under such conditions, a single color could be worked up to a fair degree without the supreme bother of thorough cleaning between mulling the different colors. However, realistically, such cleaning would be required were the same colormaker to turn out many different colors with the same singular muller and slab. I must maintain there exists no advantage with the muller's use in oil paint-making when compared to the proper knife. In fact, it is the direct opposite. The knife holds all advantages. The proper knife is a long and very thin and flexible slight taper going from 3/4 inch at its base to 1/2" at its tip. Such a knife is conveniently 3- 4 inches long. With the proper knife and proper swirling technique, any usable degree of oil-to-pigment ratio is obtained. We often read today of the old painters employing apprentices who mulled the necessary paint on a slab while the master painted. There is no sense in that scheme. Excepting white, the amounts of various colors needed by the typical realist painter on a daily basis was small; and the needed white would be barely more than small, perhaps a rounded tablespoon-full. Repeating myself, what the apprentice mulled on the slab was pigment materiale using a liquid other than oil. He was making pigment-- not oil paint (references aside from personal experience: Cennini's "El Libro'D'Arte". Also DeMayerne's Manuscript. Also Richard Symond's--1617-1660-- Italian Notebooks concerning the 1600's painting techniques).]

Though having the advantage of being freshly made, simple oil-and-pigment paint is not perfect of itself. Repeating from above, according to the many old manuscripts, it was historically usual for some painters to add a "temper" to their rubbed-up paint. This tempering caused the paint to behave as the artist intended, whether that intention was fast or slow-drying, dullness, glossiness, shortness, or longness. This tempering of the colors came usually in the form of a one-drop addition of a varnish, or drying oil (such as a thick honey-like dark product prepared by cooking Litharge with raw oil­ olio cotto in Italian), or some other version of a heat-bodied oil (which would either allow the paint to "melt" into an enamel-like appearance, or stand up in the manner of a resin-varnish use). Tempering the colors allowed drying to a tack-free state, and allowed the use of glossy oil and varnish coatings to be applied soon after completion. Certain tempering agents could allow works on canvas to be safely rolled up for transport or storage soon after completion.

Nothing has changed over the centuries; though pigments now come to our hands in usually rather consistent and well-milled fashion, freshly hand-ground paint is still often wanting in character to the whims of the master. By itself, some hand-ground paint colors will be stringy. Or, the paint may have slumped soon after rubbing or while being stored in tubes. These un-desired conditions are expeditiously remedied by the HB-Oil. A drop of HB-Oil is added and the paint then behaves, stands to attention and produces excellent painterly brushwork that is "short" but has the character or being "long" in appearance.

The surface to be worked upon is oiled-out with a thin coating of a preferred raw oil. The HB-Oil is added in one or more drops as a temper to the paint which is then applied using hog brushes or softer tools. Paint can easily be applied wet into wet without trouble. Typically, with handground Linseed oil paint, the HB-Oil paint dries flat as if wax had been added. This flat appearance is caused by the odd effect of the HB-Oil sinking into the paint rather than rising above it, as is usual with other tempering agents.

Drying of paint made with the HB-Oil is expedited by a short exposure of the painted work to full sunlight (about one or two hours in Summer). The dull surface allows easy over-painting above the dried work. In completion, after the painted surface has dried to a tack-free state, a super-thin coating of the HB-Oil should be applied straight from the bottle to the total work using a fast scrubbing manner with a hog-hair brush (to illustrate, 12-15 drops of the HB-Oil will cover a full 18"x24" surface, though only the dull areas require the application). The work should then be immediately placed in sunlight for one hour causing the thin layer of HB-Oil to dry quickly to a tack-free and perfect uniform shine. No cracking will occur and no final varnish will be needed later on; the work exhibits a soft shine and is ready for the client.

Illustration: "Moonrise with After Glow". Here is a sample, shown slightly larger than the original 11X8 inch work, made using handground paint with slight additions of the HB Oil. This was done alla prima and exhibits the painterly character engendered by use of the HB Oil. My personal preference would be to complete the work by adding another layer of HB Oil-tempered paint, especially within the sky areas:

As with the Gentileschi Amber Varnish, one bottle of HB-Oil will last a long time. The HB-Oil is harmless: it is walnut oil cooked to an amazing and non-yellowing state; the oil provides a manner of obtaining resin-effects without resin use.

James C. Groves

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