Our Genuine 19th Century Copal Varnishes

Amber varnish was a difficult thing to find during most of the 19th century. Copal had long since become the resin of choice in commercially-prepared varnishes. Copal was 'easier' to melt into oil, yet it provided great durability. Consequently, artists wishing to add backbone and character to their oil paint reached for copal varnish. Versions of copal varnish were eventually formulated to be better-suited for artists. It became very commonly used.

Our "19th Century Copal Varnish" is similar to our "16th Century Amber Varnish", though it is formulated with the very same copal that has been common to European varnish makers and artists since before the time of Columbus.

Above image: Detail of a small oil painting I made using our Cole's Copal Varnish. The captured oil paint, placed with conviction, permanently shows off the cleverness of the stroke.

What exactly does a copal varnish do for oil painting technique?

As with amber varnish, just about any copal oil varnish will strengthen basic pigment-and-oil paint, allowing increased resistance against humidity, oxidation and ozone-attack; which adds durability in paint film structure and pigment color-retention. The actual paint is tougher and harder against mechanical wear and chemical solvency. Additionally, the saturation of color becomes noticeably ‘cleaner', more brilliant and 'shining'. Then there are the sought-after effects of texture ; and copal — like amber— has long been prized for this particular attribute. Realize, few copal varnishes exhibit this ‘stiffening' or congealing trait to anything more than a slight degree. [While, in fact, copal varnishes high in oil-content may initially produce this firming effect when a droplet is added to the paint on the palette, yet they fail in a matter of an hour or so, the paint slumping and becoming useless for many intended 'painterly' efforts. Thus, as a painter, I believe the better copal varnish will always contain a high amount of resin ; and this supplies the required texture throughout the day. Besides, if the need arises for more oil, then that can be easily added at whim.]

Some history on copal varnish use

I wish to point out that hard copal oil varnish was a substance widely respected and used by the greatest painters during the Victorian period (to name just a few, Gerome, many of the Hudson River painters, John Constable, Mulready, and most everyone of the Pre-Raphaelites spring to ready allusion). This varnish is mentioned in most 19th and early 20th century oil painting handbooks as a proper medium for getting paint to be what it could be. During the impressionist period, alla prima painters loved copal, though the earlier parts of the century saw it in favor to multi-layered techniques requiring glazing and scumbling. This type of varnish is termed an "oil copal" varnish to differentiate it from a "picture copal" varnish, which would be a spirit varnish version used as a final coating on a finished oil, or also often incorporated into quickly setting early layers of the work where an oil varnish might be too slow-drying for isolating needs-- see more below. Oil copal could be obtained in either a pure form or a fast-drying version made with drying oil. Curiously, it appears that spirit copal can often be detected in old oil paintings. In contrast, and according to the latest GCMS studies undertaken by todays paint-chemists, the detection of oil copal (amber may also be inferred) hard resin varnishes seems to give only findings of "heat-bodied oil" (for recent instance see "Pre-Raphaelite Painting Techniques" by Townsend et.al., 2004, Tate Gallery, page 78).

Though it can be used alone in scant one-drop amounts added to oil paint, copal oil varnish is often also effectively used as an ingredient in painting vehicles. For instance, added to standoil, this varnish allows modern tube colors to become "longer" and gives a melted appearance without the paint soon "running" or trickling down the support. Except in such tube color-use, where a poly-oil addition helps allay the dreaded 'suede effect', there is no real need for a polymerized agent such as standoil when using this type copal varnish, as it typically contains about 50% polymerized oil resultant from the high temperature cooking process required to combine the resin with the oil. And so, when considering making painting mediums intended for handmade oil paint, a dilution of this varnish with turps and raw walnut or linseed, or even some sort of drying oil (best made with lead) creates a perfect balance for thinning the artists home-ground colors. Such a medium allows easy painting and a nicely brilliant shine ; and if this medium is made using drying oil, or, barring that, cobalt or manganese drier, the result is paint that dries in one or two days.

Another use: many painters simply added a drop or two of straight oil copal per teaspoonful of Meguilp, making that jelly materiale much stronger while not harming the actual gelation. The famous Roberson's Medium was such a compound of Copal varnish and meguilp. This addition to common meguilp was very popular by the 1860's. A drying-type copal varnish, i.e., one that is cooked with lead, is most suited to this purpose.

George Field was a 19th Century color-maker and painting materials afficianado who, in 1835, wrote an encompassing manual helpful to painters and students. In his revised edition of "Chromotography; a Treatise on Colours and Pigments", 1841, Field mentions (page 361) that John Constable's painting vehicle was composed of Copal Varnish, leaded drying oil, and turpentine -- often-times with an addition of beeswax cooked into it. Anyone today marveling over Constable's English landscapes should be able to bear witness to this vehicle's lasting performance.

Other great landscape painters used copal varnish with their colors. According to a note written by Thomas Cole to A.B.Durand, asking Durand to buy colors for a then up-coming sketching trip into the Catskill mountains of N.Y., Cole favored the use of copal varnish to aid the drying of his bladder-enclosed paint.

Here is Cole's note (June 9th, 1837):

"You said you wished me to give you a list of colors. I scarcely know what can be got in bladders, but I think the following. White, Roman Ochre, Sienna Raw & Burnt, Burnt Umber, Chrome yellow, Naples yellow, Antwerp blue, Madder lake, Vandyck brown, Light red, a little oil, & some Copal varnish in a vial as a drier. Vermillion & even Chrome yellow we may carry unprepared and a little Ultramarine. Camp stool I think you ought to have. Camp umbrella if you can get one I will join you in it if you like. It will be well to get two sets of colors one for you & one for me of course the bladders must be small the white the greatest quantity." [NYPL, A.B.Durand papers, box 3, folder 6)

Cole's mention brings up some interesting Q's as to what sort of copal varnish he was referring to. There were numerous recipes for varnishes containing copal. Some recipes referred to "gum copal", which might just as easily have been the soft, freshly gathered or scrapped copal found on the growing tree. Such soft copals did find a way into commerce as artist's copal varnishes. But the hard copals were sought for the strongest copal varnishes and I suspect Cole's variety was just such a hard copal type. Typically, coach varnish of the time called for expedient drying, and so it was cooked up with "drying oil" --an oil, likely linseed previously heated with some amount of lead (litharge). Such a varnish was dark-- what some might call "dirty", but it dried clear and tough to the elements. Further, as only a titch of it was needed, its color would have no real effect on Cole's paint.

Cole's letter provides another clue. He tells Durand to also purchase some oil (immediately before notating the vial of varnish). And so, one might surmise the two thoughts were linked in Cole's mind. He does not mention turpentine, an agent generally used with oil painting during the 19th C. Perhaps Cole used an all-oil technique, without need of a solvent to thin his paint? Then again, copal coach varnish often contained turpentine, which was added upon cool-down in the varnish-making process. Perhaps there was no need for turpentine in Cole's use as it was already in the varnish. [Updated information concerning Cole's likely copal varnish will be forthcoming to this website in 2009.]

Here is a detail from Cole's painted 1842 series "The Voyage of Life" (National Gallery, DC.), showing the marvelous color and luscious capture of painterly detail. The works are amazingly fresh and trouble-free in appearance and, thanks to a good home and proper care at the NG, seem to have been 'painted yesterday'. The vegetation shown may have been painted at once using lead white in thin and thick application ; then, once dry, overpainted with yellow, green, and blue. I cannot say this for certain but I do know using some good oil varnish in one's paint allows otherwise troublesome manipulations to be accomplished without generating subsequent harm (creeping, cracking, fissures). The clever appearance of Cole's brush-sculpted paint and its ability to resist flattening over time also match nicely with the use of copal varnish.

Cole was also known to varnish his works with copal varnish. According to W.S.Mount, a painter who had some physical aquaintance with the landscape master, Cole used his regular copal varnish mixed with turps and a few drops of oil for this purpose (Mounts personal diary, April 7th, 1848). [Mount also indicates in his notebook (May 31, 1857) his own use of copal varnish with raw oil --equal amounts, together-- as a medium. He likely used it in the general manner ; which was as an addition to the colors and for oiling-out before commencing to paint.]

By itself, straight, copal varnish could be directly added to oil paint though it could not be used for 'oiling out' as it gets gummy far too quickly (note: this sort of copal varnish is sticky stuff and hard to remove from the hands-- something stronger than dish-washing liquid is necessary). For the purpose of oil-out, it requires some additional oil (as noted above), or simply straight oil alone can be used. It might be that Cole needed the raw oil for making his oiling-out medium. As with Mount and other painters of Cole's circle, one part oil to one part of the copal varnish would do the trick nicely ; and with the use of certain copal varnish-types, with or without wax additions, a jelly-like substance could be created by combining the varnish with the oil. Cole's (and his student, F.E. Church's) work does seem to show the use of such a 'copal jelly'.

[Note: As a drying agent, lead has a long history of being the means to creating a "drying oil". Some call this "black oil" today, but there are ways to make it very drying without actually turning it black. Still, one sure though safe side-effect when using lead products (such as litharge, red lead, or lead carbonate) as drying agents is their characteristic trait of making the final product turbid; that is, cloudy. This cloudiness is due to the formation of lead soaps within the oil-- and, by extension, also within the final oil varnish. Within days of cooking, these soaps precipitate out of suspension within the oil, forming a sludge upon the bottom of the container. Again, these soaps are safe and not harmful to oil paint, and dry clear if again shaken into the varnish. Then too, the clear part of the varnish can be carefully decanted from atop the sludge-layer. Anyway, aside from appearance, this initial cloudiness is not otherwise a problem. In fact, the lead soap is actually a paint-film strengthener. For the curious, know that this lead soap info arrives according to the latest research into driers used in artist's materials. Still, the somewhat darker color and cloudiness is enough to sully the clarity of the final varnish. As such, the few makers of hard resin varnishes today will keep away from cooking lead oxides into their formulation, and perhaps substitute other linoliates/resinates instead, such as cobalt drier. Then again, if the artist wishes a faster-drying paint, he need only add some drying oil (like 'black oil') to the grinding oil or paint pile.]

Another landscape painter, W. Laidlay, also recommended this sort of drying copal varnish. Laidlay writes: "I am bound to admit that, except that it is dirty and sticky to handle, copal makes a very serviceable and permanent medium." (we might fairly presume Laidley uses the word "dirty" to indicate "dark"). Laidlay further states: "Although the experiences of twenty or thirty years counts for but little in a question as to the permanency of either colours or varnishes, I may mention that none of the sketches and pictures I painted with copal have changed in the slightest; and that I have very good authority for believing that that very excellent techniquist, Dyce, painted with copal. This last, I consider, a valuable certificate, as many of his pictures are very high in tone, and as far as I know, all of them, even where green was used, have stood well. I don't know that I ever saw a more realistic and beautifully finished piece of work than the ivy-covered tree in Dyce's picture recently exhibited in the Franco-British Exhibition in 1909. One of the merits of copal is that you can paint more coats, one over the other, without producing a leathery surface, than you can with other mediums, and in support of this assertion, I may mention that I have it on very fair authority that Dyce painted some of the detailed pasages over a thin grounding of copal and white." [pages 259-260, "Art, Artists, and Landscape Painting" London, 1911. Note: see the passage delivered from Holman Hunt cited at the end of this report for a brief about this technique.].

As I said, it would appear that this copal was a quickly-drying version, though it might possibly have been a spirit-type copal varnish, which I will cover in more detail below. This drying-type copal varnish is made nowhere else today, nor do any mediums I have found perform like it. And so I offer my own version for artist's use. Our clear and light 19th Century Drying Copal Varnish was formulated to dry in approximately one day, and utilizes lead as the drying agent.

There are various ways to use this varnish. For example, our regular 19th Century Copal Varnish or our Drying Copal Varnish (DCV) can be added to home-made oil paint, in small one or two-drop amounts straight from the bottle. This tempering produces an amazingly crisp paint that matches Rembrandt's painterly impasto. This was a method used by J.F. Millais to form the stiff underwhite necessary for his luminous wet-into-wet technique ( covered at end of this report). Thomas Moran seems to have used the same type copal varnish for his impasto-ish underpaintings in white and black. Some painters first stiffened their paint by adding drops of the pure varnish ; then painted away by dipping their brushes first into pure turps, then into the paint. Or, they simply thinned their stiffened paint with the turps using the knife and went at it in that manner. This method allowed the paint to be brushed on easily, fluidly and without need to 'oil out'. Soon enough, the paint became 'set' after solvent-flash, allowing gentle overpainting without need for drying of the underpaint ; further, the varnish addition increased binding strength beyond what the mere oil could supply.

Another method was to make up a painting medium. A medium-- also termed a vehicle-- is a compounding of various painting ingredients that can easily be added to the basic paint to provide ideal character preferred by the individual artist. One typical medium -- a drying-type copal varnish mixed with equal parts of turpentine and oil -- was used to create so many of the greatest productions of the 19th Century. Generally, this copal painting medium imparts brushing-ease while retaining crispness, giving the paint a thixotropic quality. It also provides some degree of 'set' as the turps evaporates, allowing clever build-up of wet paint. Thus, this basic medium is ideal for alla prima technique. Because it dries quickly, this medium is also perfectly suited to layering. Above all, the medium allows lasting paint effects that remain just as the brush leaves them-- there is no slumping through time as the simple oil would otherwise slowly and actually oxidize (evaporate), becoming more level with age. Nothing more is necessary and the work matches the brushwork as seen in Cole's, Bierstadt's, and Moran's painterly creations. [Realize, these artists used bladder or tube-kept colors that were pretty much aged and slumpy as they were squeezed onto the palette. The colors were also slow drying, as Cole pointed out in his letter to Durand. These problems were negated by use of this drying copal varnish (or the medium made with it), which, when used as described, produces a fresh and marvelous texture that behaves itself and, when combined with walnut ground paint, will remain fresh and lively for good. Also note: the classic three-part medium was mentioned in many how-to books on oil painting in the past 200 years. This "three-part medium" is still much used today. However, it never matches the results found by use of the better 19th Century drying copal varnishes.]

As I am a fast workman, I personally consider the Drying Copal Varnish preferrable. 19th Century Drying Copal Varnish (80 mil. @ $25.50) is listed on our online ordering form .

The following recent 2003 work, "Morning Moonset" (24x30 inches) was created using paint rubbed-up to a creamy condition, then a drop of Drying Copal Varnish was added to each color. A copal medium of one part DCV to one part walnut oil and one part turps was used as the oiling-out vehical. On a dried white ground lubricated with the copal medium, the work was first drawn in with vague delineations to establish basic composition. Then, while all was still wet, it was painted in full dead-coloring, this accomplished quickly and roughly using very common hogs; allowing all course brushwork to remain. Paint was used generously--almost thickly-- in the first layer, then the whole was allowed to dry overnight ; whereupon it was more carefully brought out to true coloring and finished one section at a time using, again, the same type paint thickly-applied with clever and suggestive brushwork giving a sort of physical 3-D effect to the whole. After drying, all sunken areas were given a thin scrubbing application of the constructed DCV medium. This super-thin coating replaced the lost (sunken) protective and gloss-giving pelicle, resulting in a pleasing overall shine once again. [Contrary to current established advice rampant throughout the oil painting realm, no harm will come from this final thin medium-application. I am simply replacing that thin outer-coating that was lost due to the sinking. Instead of causing future damage, this normally-available pelicule will promote the perfect longevity of the work; though, bear in mind there are many and various painting concoctions 'out there'. Of course, I cannot make predictions for the use of other commercial products, especially those made with linseed oil (which will soon enough take on a "gallery tone" with works exhibited indoors). Always allow that my directions are based upon knowledge and experience, but only with those varnishes/mediums I am familiar with.]

The following extreme closeup made with semi-raking light is shown much larger than true size and displays the interesting texture found throughout the work. Due to the use of the resin varnish, the lush paint topography will stand firmly against age.


Updated notice: New "Cole's Copal" offering, 2009

1836: Another letter-excerpt from T. Cole in Catskill, NY, to Asher Durrand of NYC: "Will you please obtain for me a pint of copal varnish from Feughtwhangher [Feuchtwanger] if he now has any very fine." {NYPL}

For the traditionalist desiring complete authenticity, Western Maryland Gallery now offers the very copal varnish used as the underlying additive and painting-workhorse of Thomas Cole and other circa 1830-1880 19th Century American landscape painters. The clues were always there but finding the specific copal varnish so desirable to the Hudson River Painters has taken years of trial-and-error. This varnish is slightly different from our Drying Copal Varnish. Our unique and distinct Cole's Copal Varnish is made for those who wish to retrace and follow in that technical path of the many landscape painters who utilized this particular copal varnish-- Cole, Church, Cropsey, Gifford, Kensette, Bierstadt, and Moran. See "Cole's Copal Varnish" ($25.50 for 80 mil.) on our online ordering form. Like our "Drying Copal Varnish", Cole's Copal Varnish speeds the drying of oil paint; however, it requires a solvent to occasionaly thin the copal-treated paint while working. This particular copal varnish essentially "jellyifies" any oil paint it is mixed with, allowing brushwork that is facile and keeps its place even when much-thinned with solvent. The technique is simple and straight-forward: The varnish is directly added to the paint on the palette. The brush is dipped into a chosen solvent, such as turps, then used to thin the copal-treated paint to any desired brushing consistency. No medium-making is required in the procedure. Directions for use come with this product. [Note: As a way of getting around solvent-use-- desirable by those who have less tolerance of solvents-- the paint should be thinned-downl to the desired fluidity using simple oil before adding the Cole's Copal Varnish. This noted, I would caution that one cannot duplicate the full effects of the HRS painters without resorting to a solvent.]


Our "19th Century Copal Varnish"

There was another type of 19th century copal varnish. This type varnish was not made with any siccatives. It seems to have gained favor in the later part of the century and I've noted its use by painters such as J.F.Carlson, who specified only the pure oil copal varnish-- that made without driers-- should be used for painting. This formula offers slower drying of the paint. It is preferrable by those who do not want additional agents included within their painting varnish -- those who want the copal and polymerized oil but nothing more. This varnish I call "19th century Copal Varnish" to differentiate it from the other drying, or spirit types. It contains no driers but as I mentioned, if a drier is needed, the artist can incorporate that by themself. Again, Carlson strictly prescribed this sort of copal varnish when writing his book on landscape painting (though do be aware that in Carlson's time lead was "out" and regarded as a nasty thing for oil painting purposes).

The 20th century's F. Taubes also stood behind such a formulation, though his recipe called for cooking previously-fused Congo Copal into commercially-made stand oil-- a thick gooey honey-like oil which has a reputation I feel exceeds its actual value. Taubes' 'Copal Concentrate' product certainly tames some wicked faults of the standoil. Reports are the combination was a very good one for use with commercial tube paint containing Aluminum Stearate. I cannot argue with that. But my copal oil varnish is different and is decidely much 'shorter'(crisper) in produced paint-texture. [ update: our copal varnish now contains nearly four-times the copal as I found in Taubes' varnish ; and this was recently discerned by using our varnish with standoil to copy the Taubes' product known as "Copal Concentrate". Thus, a nearly three-parts addition of standoil would be required to obtain the same working attributes as Taubes' Concentrate.]

Our very light and clear non-leaded 19th century Oil Copal Varnish contains a very high percentage of true copal to oil-content and is very strong in its effects on handground paint. There are no other ingredients aside from a slight amount of turps. The 80 mil. bottle of this hard resin varnish is currently $24.50. This amount is enough to make about 300 mil of strong copal painting medium ( typically one part 19th Century Copal Varnish to two parts walnut oil; moderately heated together, then one part of turpentine is added to round out the medium....some who desire flowing, leveling paint might add standoil in place of one part of the walnut oil...). 19th Century Copal Varnish is listed on our online ordering form .

As an aside here, Taubes encountered much resistence to use of oil copal during his lifetime. It seems all the other experts, most of them amateurs -- some totally non-oil painters-- vehemently railed against copal and amber resin varnishes and their use with oil painting (as for amber varnish, the experts decided that was actually impossible to create). Of course, I have read these expert reviews and can find nothing to indicate these fellows ever actually tried true copal and amber oil varnishes. What I am saying here is, the expert's words do not indicate any familiarity with such varnishes; yet they speak with great authority.

[ Frederick Taubes wrote that the single source 'scientific' test used to decry and throw all copal varnishes into the rubbish bin was actually a common hardware-store variety floor/coach copal varnish. Any varnish-maker knows that varnishes can be made in a great variety of way and means. One fellow's copal varnish may behave quite differently from another's. Considerations must be made as to the kind and amount of oil used in the cook. Also the type and amount of resin. Driers, like lead, can be cooked along with the ingredients, or such driers can be added after the cook. Even this 'play' with the drier makes a difference in the performance in the final varnish. Because I am an oil painter and have dedicated my research to painting effects and techniques, many of the varnishes I've concocted failed to provide the specific abilities I require. One size does not fit all. Indeed, there are too many ways to make varnish. In the 19th Century, a cabinet copal varnish was very high in resin-content and turpentine but less oil. This produced a hard finish that could be soon polished to a high gloss. By contrast, an outdoors varnish was high in poly oil-content. Such oily varnishes were often very tough to outdoor weather. Well and good, but, as Taubes would say, there was no attempt by their manufacturers to make them otherwise suitable for actual oil painting. Formulas from the period show that some of these common copal varnishes contained 6 or 7 parts linseed oil to one of the copal resin! Such high-in-oil-content varnishes will yellow and brown indeed. Let's face it, oil paints and additives can be made poorly, but we want those products that are made well. Personally speaking, I have made this outdoor-type copal --and amber--varnish on many occasions. Due to the addition of strong driers and simmering it all at a moderate heat for some 6-8 hours, it becomes very dark and fast drying. After sleep-aging for some months, such a varnish becomes suitably toughened and it does stand amazingly well to the weather ; but I have never actually painted with it ; though, I suspect that, even with this type copal varnish, a simple droplet added to my paint would not likely produce future harm ; but I'd never load my paint with the stuff! Remember, the old Strasbourg manuscript directed that only a drop or few of varnish was to be mixed with all the previously freshly-rubbed-up paints.]

The slighting practice and commentary against hard resins continues today. In our age, modern synthetic resins are the vogue. Within every decade, it seems a new version of synthetic resin arrives upon the scene which has passed all accelerated aging tests with flying colors. The amazing chemical wonders are thereafter put into commercial use and exhibit failures within the following ten years. Heedlessly, the next chemical wonder arrives to replace the 'bady' and is then touted as, finally, the ultimate painter's resin. [ I hate to anger anyone by this commentary but I do read the journals and this does happen like clockwork. And so I've stopped holding my breath. I'm not waiting on the experts to tell me what to paint with. Instead, I look forward but also backwards where I best seek the better means derived from the historically tried-and-true. ]

An interesting account of the British painter John Linnell and his decision to use copal oil varnish within his own work can be found here. Linnel was so adamant about obtaining only the better copal and amber varnishes that he hired a varnish maker to make some under his direction and on his own premises. Linnel's painted works stand today in fine condition. Not surprisingly, Linnel's friends also wanted in on the act. The painters Webster, Mulready, and Creswick, got with Linnell and conjured their own copal varnishes, too. In 1853, the group affectionately offered up an ample amount of their copal brew to the Pre-Raphaelite painter, Holman Hunt, who was still using his gift faithfully some 40 years afterwards. [See "the Graphic Arts" by Philip Hamerton, 1902; page330. Prior to this gift of copal varnish, Hunt obtained his copal from Roberson, a famed London colourman.]

Spirit Copal or Picture Copal Varnish

Another formulation common to 18th and 19th century-use was pure fused copal dissolved into various turpentines. As such, this varnish is a spirit varnish. It was generally termed "picture copal" and was often used by some artists as an agent within the actual paint. It gives the paint a strong texture, making it perfectly short. Though quickly "drying" by its solvent evaporation, it doesn't truly alter the drying of the oil paint. But, once dry, I must suspect it allows such paint to stand at attention for centuries. I personally think it best used as a paint storage stabilizer or as a final coating on finished works. I have found mention of artists adding a few drops of oil to give it some elasticity before using it as a final varnish but I think that unnecesary if applied as it should be --and that is super-thin. When coupled with oil, it forms cloudy rather than clear unions and eventually precipitates out of suspension; that's because it doesn't truly combine with the oil. It can, however, be used to make high-temp varnishes once the turps is flashed off, but that is a combustion hazard and I do not recommend it.

Thomas Cole certainly used spirit copal varnish with a few drops of linseed oil as a protective painting varnish; and Bierstadt also recommended it for a final varnish for his works, though he advised adding a few drops of poppy oil to it for the less-yellowing consideration. I'll easily assume many other masters did the same. Their works are lasting fine.

Also, picture copal just may be the means behind the vigorous and clever brushwork found in the underpaint of Thomas Moran's works -- though I would much favor the DCV type for that purpose, and both deliver the same effect. However, unlike the spirit copal, the DCV greatly speeds the drying of the actual oil paint.

Whatever the type utilized, judging from Cole's (and Bierstadt's, Moran's and many other's) works made during that great century, it seems likely a good oil copal varnish medium may well prove to be as tough and lasting as the Renaissance Amber varnish.

Use of our regular and drying-type 19th century Copal Varnishes to make mediums [Note: this section does not apply to "Cole's Copal Varnish".]

Neither the regular copal nor drying copal oil varnishes we produce are mediums or vehicals for thinning oil paint. Rather, both are additives. That is, from the bottle and in pure form, they are used only to condition paint by typically one-drop amounts. As such, oil paint is first worked up with raw oil to an easy painting soft creamy texture, THEN a drop or half-drop of the varnish is added. Afterwards, the paint will keep its place and dry glossy, firm, and retain its fresh-appearance for a very long time. Note: again, many copal and amber varnishes will, at first, provide a certain shortness, or crispness to handmade oil paint. However, depending on resin-content and other factors in makeup, this crispness may disappear within the mere interval of a half-hour, leading to a slumping of the paint before it can be used. Not so with our varnishes. The superadded effects remain throughout the day. Please realize, this valuable characteristic alone was achieved only by countless trials with differing formulations of varnish.

Copal varnish can be used to make very effective mediums. A medium is a helpful painting-expedient, especially to stiffly-ground paint. In other words, the oil paint is first rubbed up to a barely useful heavy mass, then thinned with a medium to a desired painting consistency and character. Tube paint whites typically come to us in such stiff condition. Thus, tube paint requires thinning to become better useful to many and various painting techniques. Some handbooks decree such thick paint needs only turpentine or equal parts of turpentine and oil to do its best. I would maintain otherwise. Turps alone, when simply added to impart easy fluid brushing and careful delineations and detail, often causes the paint to be underbound. Thus, it is soft and weak against abraison/ future cleaning. Additions of tough varnishes, like copal and amber, overcome this weakness, and certainly add optical qualities not available to basic oil-and-turps alone. Plus, very important, the varnish allows the work to dry to a tack-free state, not a gummy state -- a condition common to layered techniques especially--as with turps-and-oil used as the paint-deluent.

Oil Painting mediums involve adding certain agents to achieve a fluid carrier balanced towards every whim of the painter. Solvents produce thinning and, with evaporation, they allow 'set'. Driers can also be utilized ; and they perform as their name implies (many hate driers ; I like them. They do not actually dry oil paint ; rather, they solidify the paint faster than normal). More oil will help soften paint and provide for a more fluid brushing quality. Copal varnish provides all those meritable functions already mentioned. Wax or other gelling materials can be melted into a hot medium so as the material acts as a floculent-- thereby causing the brushwork to freeze in position. Mastic, bentonite, aluminum stearate, all, will also perform such function. As to proper use, once conjured, a medium can be used either as a paint additive or as an oiling-out agent. [ Note: Strong copal varnish, unlike strong amber varnish, may often create cloudy mediums ; this cloudy appearance is in no way harmful to paint and can even bring congealing effects into the mix.]

It will be noted the simplest, most basic medium follows the age-old 'equal parts turps/varnish/oil' approach. But, when the painter is given a strong (high-in-resin) copal or amber varnish, there is ample room for many other ratios and ingredients. For instance, increasing the oil-content in one's medium will make for more slippery effects ; yet, the paint will still keep it's place, due to the stabilizing effect of the copal. Further, to help alleviate the too-short-nature of many commercial tube whites, standoil or other poly oil may be added to the medium. Yes, it works.

Gel mediums, so popular in the 19th Century, are traditionally made using a bit of wax heated into the medium. [ Be careful, as the heating may cause the solvent in the mixture to become a flamable vapor!]

Another very basic medium imparting excellence of surface is that recommended by the landscapist Carlson; i.e., 1 part oil copal to 1 part gum turpentine and this added to the tube colors or freshly rubbed-up oil paint. However, I feel the type of oil copal available to Carlson was not as strong in resin-content as our own regular and drying versions. His copal varnish appears to have been more of a medium than a varnish. That is to say, his varnish likely contained much more oil....so he didn't have the need to add more.

As with so many fine 1800's painters passing into the 20th Century, Carlson "loved" copal varnish and it would be insightful to study his works; see the painterly surface and lasting qualities of the oil copal he so effectively utilized (the type of copal used in Carlson's oil copal varnish remains unknown; it may have been either a soft or hard material. Me, I have no doubts his work is standing well. Again I will say, though it was sometimes scorned by some "authorities" within the 19th Century, soft copal varnishes used as painting ingredients seem to last perfectly well).


Paintings done alla prima may dry shiny/glossy and ready to leave the shop. However, with layered techniques, sinking of gloss will likely occur. A super-thin application of the DCV, pure, or a medium made from one part walnut oil to one part 19th Century Copal Varnish, will provide the perfect means for a final over-all appearance. Such a medium can be effectively utilized as a super-thin final coating if applied to paint that has become no longer tacky and rested a week or so afterwards. This final coating should be thinly scrubbed over the entire work, or, at least, the last-to-be-painted sunken areas, using, say, a half-inch hog brush. Afterwards, the painting should be set in direct sunlight for about an hour, then brought inside whereupon it will be fully dry in 12 to 24 hours. The painting requires no further treatment 'down the road'. The finished work is ready for the client. [Important note: directions given herein apply only to copal varnishes made by us. Other makers produce different varnishes which likely will not perform as our varnishes. This applies to all of our varnishes, both copal and amber, especially as these varnishes are made using walnut oil and a higher resin-content to other known varnishes.]

Below is a 24x30 inch recently completed oil showing the light effects of mid-afternoon sunlight on the Youghiogany River in Western Maryland. The initial paint was freshly made, rubbed up with the knife using unrefined walnut oil to a rather thick consistency; then thinned for a creamy brush-manipulation with a little of the DCV medium. The medium was also used to lubricate the ground before commencing, as well as between layers. The work was dead-colored in two layers. A third layer was utilized to administer the atmospheric haze and chromatic light effects through glazing and scumbling, and highlights where the sun sparkles in the rushing water were applied. The work is quite vigorous in its brushwork topography. After total drying, a final super-thin application of the DCV (straight with no thinning of walnut oil) was scrubbed over the sunken areas and dried overnight to an over-all and pleasing sheen.

James C. Groves jamescgroves.com

Notes and updates, December 2002.

I recently came across some interesting information on the web at the site of the Canadian Conservation Newsletter(CCI)of June 29th, 2002]. I have underlined key points of consideration.

(Quote)"The paintings of the Pre-Raphaelite Brotherhood have been a subject of interest for many over the years — at least in part because of the availability of primary source material such as letters and biographies. The startlingly bright colours, the distinctive paint application, the legendary use of zinc white as a ground with paint applied on top wet-in-wet, and the pristine condition of the works are all cited frequently and uncritically in the art historical literature. Tate conservation department is currently in the midst of an extensive research project to examine, record, and interpret the actual materials found in these artists' key works.

One specific material issue is the well-documented use of copal resin both in the paint and as a varnish. Unfortunately, an initial analysis of samples taken from a range of works documented as including copal resin failed to confirm its presence. However, refractive index measurements of paint that were made at Tate gave high readings — which clearly suggested that linseed oil was not the only binder and that copal was a material worth investigating in this context."

I and others will find this info very interesting. Like the article states, the Pre-Raphaelite painters were known users of copal varnish both in their paint and applied as a coating (according to Speed, H. Hunt switched to amber in his later years). This copal varnish was most likely an oil copal varnish, which is copal combined with oil at a very high temperature.

Please know that there have been studies made where the researchers said that they have in fact detected copal being used in 19th century paintings. How can some researchers detect copal while others cannot? I mean, they do use the same equipment/tests, right? I submit the reason is this: the paintings showing copal found were made using a spirit varnish--not an oil varnish. What's the difference? Well, a spirit varnish is made by dissolving the resin in a solvent-- such as turpentine. Once applied, the solvent evaporates away leaving the pure resin behind. This pure resin can then be detected later by its "fingerprint"; and this is rather easily done.

But an oil varnish is an entirely different critter. With an oil varnish, in order to make it fluid for painting use, the resin has to be cooked into an oil, which typically requires a great heating-- in the case of copal and amber this temperature would be in excess of 600 degrees F. Under such an altering treatment, would the resin keep its fingerprint?

For comparative consideration, I might mention that a criminologist using water and cotton Q-tips to dissolve dried blood from a crime scene would have little problems later achieving various blood-tests with good accuracy. However, imagine that instead of plain water, that water were subsequently boiled (212 degree F.) with the blood. Would the blood undergo any change in its fingerprint? And how about if the blood were cooked in oil boiled to above 600 degrees F.? Would its fingerprint survive that? I don't imagine it would or could in either case. The heat-treatment actually destroys the fingerprint.

And so now we have a clue as to why modern paint-chip analysis cannot find 'resin-markers' in known-to-be-painted with oil varnish works. The tests only seem to give readings of "heat-bodied oils" in the mix (and know that this finding of heat-bodied oil is rather rampant in many of the toughest old master works --works made well before the 19th century).

And so here is the implied crux of the failure: You see, if modern day scientific tests of paint chips fail to show hard resin-use in known-to-be-resin-in-oil-painted 19th Century works, then, assumably, those same scientific tests previously undertaken with the old master-works --and showing no resin-use-- are also highly suspect. Thus, it would seem the painting experts today --experts who declare no resin-use (like amber or copal oil varnish-use) in the preliminary and intermediate layers of olden master-works --are only supported by tests which apparently cannot actually detect certain and historically known-to-be-generally-used resin-in-oil varnishes. The only available clue to such use being a detectable difference in refractive indexes.

May the older masterworks now be subjected to these same refractive index analysis procedures.

And, for those who might be curious as to the typical Pre-Raphaelite methodology, the one which seems to be showing amazing longevity, I hereafter give the master Holman Hunt's description of the typical pre-Raphaelite technique. Be aware, his and other's works are not the result of today's museum restoration attempts; and instead, these paintings have been displaying their sound execution since their creation. [I know this because a judicious survey of several books written from the mid-20th Century and dating back towards the time of the brotherhood always agree these works (for example, H. Hunt's paintings ) were lasting very well. Also be aware this flies in the face of the typical 20th C. pronouncements maintaining copal and amber oil varnishes as the sure means to painting extinction (as in Mayer, Doerner, others).]

(Quote from H. Hunt) "Select a prepared ground originally for its brightness, and renovate it, if necessary, with fresh white when first it comes into the studio, white to be mixed with a very little amber or copal varnish. Let this last coat become of a thoroughly stone-like hardness. Upon this surface, complete with exactness the outline of the part in hand. On the morning for the painting, with fresh white (from which all superfluous oil has been extracted by means of absorbent paper, and to which again a small drop of varnish has been added) spread a further coat very evenly with a palette knife over the part for the day's work, of such density that the drawing should faintly show through. In some cases the thickened white may be applied to the forms needing brilliancy with a brush, by the aid of rectified spirits. Over this wet ground, the colour (transparent and semi-transparent) should be laid with light sable brushes, and the touches must be made so tenderly that the ground below shall not be worked up, yet so far enticed to blend with the superimposed tints as to correct the qualities of thinness and staininess, which over a dry ground transparent colours inevitably exhibit. Painting of this kind cannot be retouched except with an entire loss of luminosity. Millais proposed that we should keep this as a precious secret to ourselves."

This technique, which was initiated by Millais and picked up by others of the cause, takes a wee bit of getting used to; but it does work. BTW, not all the Brotherhood found it to their liking. I should add something else here: the use of a gelled medium will allow painting transparently atop a dried white ground without causing the 'thinness and staininess' Hunt warns against.

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