Groves' Genuine Asphaltum Oil Paint (40-mil. metal tube) $19.50



Genuine 1600's Asphaltum oil paint comes in a 40 mil. Tube 


I cooked-up my first baby-food jar of ‘asphaltum’ oil paint in 1978. I had obtained the Dover Books edition of Eastlake and was intrigued by Mayerne’s 1600's recipe. My neighbor had a fairly solid lump of 'tar' and I shaved-off some chunks and melted that into linseed oil. I added some japan drier and the blackish gook looked rather enchanting. I used the paint in several monochromes and, honestly, to this day, the stain-like brown never showed any faults --excepting its well-known penchant of not keeping the stroke as placed. It spread and ran down the ground. I included a bit of wax in my next jar but I soon went back to using a mix of iron red and black for my preferred brown. After all, excepting Mayerne's saying it was a fine and usefull brown, every other expert-source in the last three hundred years pretty much condemned the stuff.


I later learned that I had not actually made true asphaltum oil paint. That revelation hit me after the internet was born and I was able to finally lay my hands upon the genuine naturally-occurring material. You see, true asphaltum oil paint is not made from tar or the various artificial ‘asphaltums’. True asphaltum oil paint is created from a solid 'glass-y' rock. After making the actual oil paint a hundred times I found out much more about it. If conjured in the correct manner, true asphaltum will work nicely beneath the brush, dry perfectly within a day or so ...and keep the stroke nearly as placed, such that no other additive is necessary.



A mysterious historical brown of exquisite transparency


As far as I know, no modern-day artist paint manufacturer offers real asphaltum oil paint. Many paint-makers do make up an artificial version, so-called 'asphaltum paint' made using various mixes of natural and synthetic pigments. I am convinced this current situation is a mistake based upon faulty or unknowing beliefs. Myself, after closely studying the material through many years of trials, I can find no real fault with the true and historical asphaltum-based oil paint; and as the actual paint is not offered elsewhere, I will supply it for those interested.


What is asphaltum? Asphaltum is a naturally-occurring "resinous" form of carbon typically found and mined in large seams. It is quite stable in its natural form, though it can melt if subjected to enough heat. Contrary to what has been written about it, true asphaltum is not the same as bitumen. In the mining industry bitumen is used to refer to what we today call "tar". Bitumen is that plastic gunk that occurs naturally, though, like asphaltum, it may also be created through crude oil distillation as well as the heating of many other carbon-based materials, such as the venue of coal-processing into coke. Bitumen occurs naturally in pockets here and there within the Earth's Crust. When encountered upon the surface some such pockets are often called "tar pits". Chemical analysis shows asphaltum sharing some of its constituents with bitumen; however, asphaltum is a hard brittle rock, it smells different, and is not so easily carried into solution within an oil or solvent.


Both natural bitumen and asphaltum are said by geologists to have originated from crude oil, a thick liquid hydrocarbon which naturally forms within the outer fringes of the hot Mantel, then arises to the Earth's Crust. These geologists believe asphaltum is simply crude oil that has been subjected to heat to the point where it loses its more ethereal elements and becomes a true solid. That may be. Certainly, as mentioned, chemical industries can artificially manufacture an asphaltum from crude oil via heat; however, artificial asphaltum can also be created by cooking just about any organic material until it is reduced closer to its carbon base. So, just because one can create asphaltum from crude oil, that does not mean the naturallly-occurring asphaltum arrived via the same means. In fact the reverse may also be true. Keeping an open mind, it could be that crude oil derives from heating asphaltum; or crude may be a combo of asphaltum with other matters. After all, the Earth's mantel is the ultimate chemistry set and it gives off carbon in various forms. [Note: There is some evidence that bitumen could be the half-way material composed from asphaltum that has been impregnated under heat with crude oil. Here is an interesting historical tidbit: (Quote)"I have at this time specimens before me which prove these gradations; and I have seen a remarkable instance in a bitumen brought from the Island of Trinidad, which exhibits mineral tar passing into mineral pitch, and lastly into asphaltum" -- William Nicholson; page 203; Journal of Natural Philosophy, Chemistry and the Arts, Volume 2, 1799.]


What ever its causal formation, the natural hard transparent 'glass-like' asphaltum 'rock' appears to have been formed in its hot molten state, then jettisoned from the Mantle to the surface via large cracks in the Earth's otherwise stratified Crust. Thus, seams of the brittle asphaltum often appear in vertical veins slicing through and perpendicular to the normal parallel rock-strata. In other words, the molten asphaltum has simply filled-in extant fissures in the rock.


Unlike tar (bitumen) asphaltum is not physically plastic at normal room temperature. While under heat it does become plastic and can even become a thick liquid -- in great similarity to a pine resin. Once the heat is removed, the asphaltum again solidifies into a hard brittle matter.  


Asphaltum has found use in oil painting since at least the 1500's. Contrary to common belief, asphaltum forms the basis for a very durable and hard paint. For particular example, asphaltum was a major ingredient of that black laquer Henry Ford utilized on his Model T's. Bitumen could not have met that same performance. What I am intimating here is that if asphaltum oil paint is made correctly, it will be quite lasting.


Owing to its soft plastic nature, bitumen is great for combining with crushed limestone or sand so as to make our so-called “asphalt” roads. Sometimes true asphaltum is melted into the hot bitumen beforehand so as to give the whole a more durable resistance, especially in areas where a higher climate temperature requires it.


Anyway, understand from the start here, asphaltum is not the same as the plastic, physically weaker, never hardening and softer bitumen. Myself, I would never again consider using bitumen within an oil painting. I must have luckily over-powered my version with drying linseed oil, such that the never-drying aspect remained dormant. Bitumen truly has a non-drying mineral oil within it! But asphaltum? Excepting the slumping trait so-often attributed, I have uncovered no good reason to fault its use. In fact, I will step forward and be among the first to champion it. Asphaltum was carried into use by the old masters and it served them well. I am unaware of any 15-1600's example of faulty asphaltum paint. (I am also unaware of any later use of verified asphaltum paint-failure. This may seem ludicrous to some readers but here is my latest understanding surrounding the attribution of asphaltum to ‘bad’ paint: Numerous examples of unstable brown paint long thought to be asphaltum have instead recently shown to be those “safer” alternatives – See MOLART's own study concerning asphaltum-use. [Note: MOLART --a select congregation of conservators and chemical-analysts -- spent several years examining asphaltum and other bituminous materials. The only bit I found troubling was their own use and testing of an artificial Shell asphaltum instead of a naturally-occurring asphaltum ...which, btw, still showed even artificial asphaltum as a safe paint for artist's use.)



A Fine Paint ...historically Tarnished unto this Day


Somehow, someway, asphaltum went from being considered ‘safe’ within the 1500's-1600's to being thought as ‘very unsafe’ in the 1700's-2000's. I have to wonder how that happened.


There are so many references to asphaltum in materials and painting handbooks. Google books will allow you to freely peruse these info-sources. Theodore Mayerne was a 1600's painting afficionado who claimed asphaltum to be a good paint for artists. Mayerne did not record much about the brown transparent paint. His recipe is terse and will require much trial to truly fathom. He describes the asphaltum being crushed and heated into a strong drying oil until it melted and combined with that oil. This pulverization stage is typically vacant from the later handbooks.


Understand this: Bitumen cannot be pulverized, but what the miners still call "asphaltum" certainly can be.


While Mayerne's recipe was terse, by contrast, subsequent books often go into quite a depth. Unfortunately, there seems to be some confusion betwixt what is asphaltum (the 'glassy'-rock)and what is bitumen (tar). Asphaltum is sometimes described in other ways, such as where it arrives from, and that some 'long-gone' material from the Middle East was thought the secret for its safe use. Sometimes asphaltum/bitumen is differentiated by its difficulty towards dissolution. Any recipe is vague and the reader seeking answers is left with the idea that the various writers are in fact unaware of the intrinsic nature of the true solid carbonaceous material of apparent old master-use. The writers agree on this: the paint conjured from asphaltum (whatever that might be) is beautiful but nefarious and should generally be avoided in favor of other browns.


To further muddy the waters, I should also mention that transparent brown paints which somewhat resemble true asphaltum can be created from a variety of other materials. Crude oil and bitumen are the usual choices, of course ...but, as noted before, pretty much everything based on carbon, from burned pine resin to coal to wood creosote-soot collected from chimneys --even burned or otherwise oxidized dead bodies --can be used to make a glowing transparent brown. Indeed, these calcined alternatives can be combined with some drying oil to create transparent browns with similarities to asphaltum. Some chemical tests even show instances of such materials in old master paint. But these sorts of brown are not the true asphaltum, which, again, Mayerne alludes to be a brittle rock-like material that is powdered and heated into a strongly-drying oil.


Considering this, I could well believe that much of the "asphaltum" used by oil painters since the 1700's has been derived from either bitumen (tar) or a manufactured ‘tar’. In addition, many painters also used the natural lignite or ‘peat browns’, which are the humic-acid pigment-matters variously known as Cologne and Cassel earths, Vandyke brown and Rubens brown. What some today call “shilajit” is also an example of these humic-bearing browns. These other materials may also come close to the appearance of genuine asphaltum, but they do not have the same transparent color-ability. The problem is, as MOLART uncovered, all of these presumably ‘safer’ lignite/peat browns never actually harden. They remain plastic due to the humic-ingredient, which then leads to instability within or atop the physical paint-layers. The fault known as “fissuring”, where the paint-layer pulls itself apart is typical to the use of these fake ‘asphaltums’. Repeating myself, only recently have faulty paints long-assumed to be asphaltum been examined and found to be these supposed ‘safer’ lignite browns. In the meantime, according to the conservators, Mayerne’s referenced asphaltum within 1500-1600 paintings has seemingly shown very durable results. (It should be noted that asphaltum is a difficult substance to detect via the usual chemical analysis of paint-layers; yet the olden painters via historical mention did commonly use the paint for their browns.) 


Yes, Mayerne considered asphaltum proper for use. Still, asphaltum oil paint can be misused by the hands of a poor craftsman. There are ways to ‘mess’ everything up, and in some cases, using true asphaltum may indeed result in problems. It should be mentioned that, as happens with so many carbonaceous pigments, asphaltum is a powerful antioxidant, which means it will slow the eventual ability of a fixed painting oil to solidify. Thus, as Mayerne noted, only a siccative (strongly drying) oil should be used when making this oil paint. Anyone failing to make their own asphaltum without a countering siccative oil better take care; otherwise the problem arises of likely painting over slow or un-dried layers of oil paint, which goes against my own “more-flexible-over-less-flexible” rule of layering oil paint.


Relative to this, be aware that asphaltum has no real ‘backbone’ to make it stand. The reason it typically diffuses or slumps to a greater or lesser extent is because it is in fact mostly a liquid layer of oil visually stained by a micronized-through-melting color-matter. Thus, asphaltum paint is best used as a glaze. Anyone attempting to build impasto effects with a glaze is treading in unstable waters. For that to remain viable, you need 'backbone'-- a skeleton (actual hard pigment-- or a resin) to hold the skin (the oil-y binder), if you will. {Of course, asphaltum paint can be given ‘backbone’ by various means, such as wax or aluminum stearate, or fumed silica, or a resinous medium, or some other congealing additive. But those agents are not truly necessary for the proper use and longevity of this glowing brown paint.)


Asphaltum Paint and its Properties

[Note: This section is essentially a copy-and-paste from my earlier research in 2006-7, as can still be accessed on my now decade-old Fir Wax page.]


Asphaltum can be used to create an amazing and useful artist's brown --and with great permanency; though it may well exhibit a fault or two.


The good aspects? Well, when transformed into a 'paint' by dissolving or physically melting asphaltum into an oil or solvent, asphaltum produces the most wonderfully-glowing and transparent warm golden-brown color; and when applied in its opaque top-color form, it shows off an intense 'burning' blackness. Also, when this weak-tinting brown is reduced by a slight bit of white, it becomes a pearly grey that goes well with flesh, clouds, tree-trunks, and so on. Asphaltum's weak-tinting attribute produces only a minor sombering effect when it's mixed with other colors; and so it can be used as an initial underpaint for skies, etc, where another brown might wreck havoc with superimposed coloring.


To sum, color-wise, asphaltum is perhaps the most exquisite transparent brown ever found. Yet, it comes with a couple of nasty traits:


 Firstly, and as noted above, asphaltum is a powerful antioxidant when common artist's drying oils are compounded with it. In essence, the asphaltum keeps the oil from polymerizing and solidifying. That's a bad trait; and thus, whenever choosing an oil as the binding carrier for this useful brown, be certain -- as Mayerne prescribes in his manuscript --that oil is a strongly-drying one, such as one cooked with lead or manganese ; or simply add to that oil a good and proper siccative. Problem solved! The asphaltum paint will dry in a dependable manner and remain lastingly so.


A second fault concerns the physical diffusion and slumping character of the actual asphaltum paint. Asphaltum paint has a built-in tendency to not 'behave' itself. You see, when the raw powdered asphaltum is melted into its oil carrier, the resulting brown paint will tend away from keeping its exact place on the palette, let alone the panel or canvas. It spreads out a bit, behaving rather like a thick dark brown varnish, which --no surprise --is exactly what it is.


Now, some 19th C. history-searchers maintained the apparent and better performance in 'keeping its place' of the earlier "Golden Age" asphaltum was due to it being conjured from a certain extinct Middle Eastern asphaltum, one that was/is so hard that it out-performed all others.(*) That dated rationale certainly sounds tempting to believe. I've never tried any Middle-Eastern asphaltum so I couldn't say for sure. Myself, I have only tried Utah-mined Gilsonite, which is named after the 19th Century fellow who promoted it. Gilsonite is quite hard and brittle. It requires a good heating to combine the crushed glassy black-ish resin with an oil or a solvent. Again, that's the way it should be. Yes, Gilsonite is quite decent; and if asphaltum conjured from Gilsonite still creeps around on the palette -- and it can depending on how it is conjured --then I can easily infer of no other asphaltum behaving any better. [Note: Several Middle Eastern countries mine asphaltum. Turkey is one major supplier of true asphaltum. Interestingly, the Turkish mining companies also use the term "gilsonite" to describe their natural asphaltum rock, as well as to differentiate that hard material from regular bitumen. This foreign use of the term "gilsonite" leads me to accept a strong similarity in material; as well as a reverence towards the American-mined material -- I mean, it must be good stuff if other nations have adopted the same name "Gilsonite" for their own asphaltum.]


But again, the slumpy nature of asphaltum-based paint can be a serious problem for the painter; after all, we painters desire our colors to stay as placed.


The early 19th Century painter/researcher J.F.L.Merimee was aware of asphaltum's “intractible” nature. He wrote in his 1830 book, "The Painter in Oil..."(page 33): "...asphaltum, which, whether it be dissolved in drying oil or oil of turpentine, is equally clammy and intractable, for it is impossible to keep it on the palette, or yet to spread it sufficiently thin upon any part of the picture, without its running beyond the bounds required." Merimee then passed along a recipe for creating artist's asphaltum oil paint which involved much wax and mastic within the paint-mix. He claimed this transparent brown would then "behave in the manner of Rubens". Merimee mixed lead paste ("oglio cotto", which is nut oil gently cooked with half its quantity of lead carbonate until the whole becomes a clear paste) with strong mastic varnish to create a substance he described as a pomade-like painting varnish. Thus he wrote, ".... when mixed with this varnish, that tendency (of asphaltum to spread and dry too slowly) is prevented, and it becomes as manageable as the other colours."


True enough, ample wax and mastic will engender a paste-like consistence and seemingly keep the lovely golden-brown creature from spreading on the palette. Having studied and created my own true asphaltum paints (both solvent and oil-based) since 2006, I have some better news to report: Gilsonite Asphaltum made according to the olden 1600's recipe behaves fairly well. There is only a slight slumping! What I have found is that the relative amount of slump depends upon how you combine the components. In other words, the entirely conceived notion that the old masters' asphaltum lasted well and behaved itself because it was made from a now obscure source of asphaltum ....is not supported through my own anecdotal trials. Using Mayerne's very recipe for asphaltum oil paint shows that Utah gilsonite can be made into an oil paint that exactly mimics the olden material.



Making the Oil Paint 


Image below: Left sample: Asphaltum can be ground into a paint like any other pigment. Unfortunately, what you get is nothing more than a sullen opaque brown that resembles a grainy raw umber. By vivid contrast, the sample to the right shows the actual manner in which asphaltum was made and historically-used -- it is physically melted into the painting oil! Asphaltum's intrinsic character can only be derived through this manner.





For use in the creation of a paint, the brittle asphaltum rock is crushed and pulverized into a glass-y transparent brown powder; then, to show off its better transparent and colorful attributes, the powdered asphaltum can be melted into suitable drying oils (to make oil paint as Mayerne cited) or various spirits (to make spirit asphaltum, which Rubens seems to have often preferred). Depending upon the quantity and heat-level used to do this, the final asphaltum paint can possess varying traits. It may have a long shelf-life; or it may harden and "liver" in the tube within weeks. Aside from its color, dissolved asphaltum oil paint may be easily brushed-out and well-behaved; or it can be a truly troublesome critter to manage, often requiring bulking additives to make it dry and behave properly.


What I am now offering to oil painters is the well-behaved asphaltum paint with a shelf-life comparable to most other oil paints. It brushes-on straight from the tube, holds its place rather well with a minimum of slump or creep, then it dries in a day or two. Again, I use no other additives beyond the powdered asphaltum and the drying oil. As such, my oil-based asphaltum is the very paint described by Mayerne now nearly four-centuries ago..


I will provide here two images of dried asphaltum oil paint which visually portray the difference between well-behaved asphaltum as opposed to the usual poorly-behaved one. First, the usual and poorly-behaved asphaltum:






Here's what the paint should do:



It is visually and rationally obvious this second sort of true asphaltum was completely unkown to most painters by the time of Merimee. As previously noted, according to his own description, asphaltum, either made with oil or a spirit " ... is equally clammy and intractable, for it is impossible to keep it on the palette, or yet to spread it sufficiently thin upon any part of the picture, without its running beyond the bounds required."

.

My genuine asphaltum oil paint can be used 'straight from the tube' with no further addition but it must not be applied as a solid opaque bodied-color; but rather as a glaze. If thinning of the asphaltum is desired for easier application, a drop or two of raw linseed (or other raw oil) may be worked into the asphaltum with the knife on the palette. This slight addition of oil will still allow some retention of the stroke. Bear in mind, asphaltum is essentially a thickened drying oil. The seductive color contains no actual pigment as 'backbone'.* Thus, due care should be used in its application. For instance, no good craftsman would ever put a blob of thickened drying oil on a painting. That blob would soon wrinkle and remain gummy for a very long time. Remember that historically asphaltum was safely used either as a thin transparent monochrome or as a thin final-glaze. It was not applied opaquely! True, 'honest' asphaltum may be applied thinly by driving the brush, or it may be diluted with a solvent or a proper painting medium. To further guard against wrinkling, some may yet prefer to give this so- useful brown a super-added character -- some 'backbone', if you will.


Speaking towards my own practice, I will typically add an equal amount of a jelly medium to the asphaltum, such to obtain the sharpest results at whim. Origin and Fir Wax will make the asphaltum remain precisely where placed. Copal Jelly or Roberson's Medium offer nearly the same performance. All of my amber, copal and sandarac "Gelling Varnishes" work well; and so does Bombelli. I will not add wax, myself, but wax was often used to provide substantive structure. As to other means to allow 'backbone', I will assume some modern-day fumed silica would perform well. [Note* I could easily add a substance to my asphaltum to give it an excellent 'backbone' but then it would not match Mayerne's historic recipe.]


The following images show the results obtained via the use of Copal Jelly and Roberson’s Medium as additions to the tubed asphaltum paint:







The image above shows asphaltum straight from the tube (left); asphaltum combined with Copal Jelly (middle); and asphaltum combined with Roberson's Medium (right). All samples have dried. Note the increased vivacity of the brushstroke incurred via the use of the jelly-additions. Use of a resinous jelly medium also imparts the ability to use a solvent technique.


Below: Asphaltum oil paint, mixed with Copal Jelly was used to form the initial monochrome of a recent painting. A day later, after the asphaltum mono had dried, shadow-tints (dark greens, dark greys, etc.) were thinly applied using Copal Jelly atop the various areas/elements. On the third day I began putting in translucent and opaque details, allowing the optically-combined monochrome and shadow tints to subtly remain. After the translucent/opaque coloring was applied and dried, a final layer of scumbling and glazing was performed. All layers were applied using Copal Jelly. [Note: This oil painting, achieved in 4-layers, was begun on a chalk-and-glue gesso ground which was then sealed by brushing-on two additional coats of pure hide glue. After waiting a week, the glue surface became receptive and conducive to the monochrome sketch. The canvas beneath the gesso was a fairly open jute fabric. Once the jute fiber was sealed with glue, then gessoed and sanded to smoothness, the resulting surface was as stiff and resiliant as quarter-inch cardboard.]



The finished painting:






Additional


Asphaltum was still widely-used by masters of still-life, marine, portraiture and landscape painting well into the 19th Century. Naming just a few big names: William Bouguereau glazed with it. I know that Frederic Church used it on occasion, sometimes substituting it with Van Dyke brown. Moran confessed he could not avoid using it. Asher Durand was another fond user -- the discerning eye can 'pick' it out glazed over parts of his typical forest-interiors.


And in considering that last mention, New Jersey painter Anthony De Mont, who shares his ardency for the history and working manners of the 19th Century Hudson River painters, sent me a link to a very good read, which is a recent bit of research exploring Durand's paint and manner of working: http://cool.conservation-us.org/anagpic/2012pdf/anagpic2012_hartman_paper.pdf


If you are curious over Durand, who practiced in the same manner as most of the greater HRS painters, you might study this paper. Paints obtained from two of his early works plus the sampling of two of Durand's 'late' palettes are tested in various procedures. Test-resullts may produce quantifiable 'numbers', but the interpretation of those 'numbers' may add-up a bit differently. The author, L.Hartman, is a conservator with the University of Delaware.


We might do well to consider that a conservator would likely offer a differing point-of-view than some of us who live by the brush; and pertaining to a conservator VS painter's POV, I will offer something which may involve the subject of this web-page.


As a painter versed in the manners and techniques of the HRS painters, my own eyes tell me that both palettes examined by the researcher are serendipitously-preserved examples of Durand's "finishing palette" , also known as a "glazing palette"-- meaning both palettes were set-up for introducing the final glazes and scumbles most 19th Century masters would ultimately incorporate into their painted efforts. The 'dead give-away' is the broad mass or "pudde" of fantly-yellowed but clear medium deposited by Durand in the central area of his palette. Realize, glazing and scumbling was commonly performed by introducing fractional amounts of color into this mass pile of medium "on the fly", then 'tested' out onto the painting. [To further explain, the ample deposit of a transparent and thixotropic medium would expedite the practice of glazing --the palette acting as a trial-and-error background, the surrounding/ringing color-daubs being 'picked' with the brush-tip, then carried over and stropped into the large puddle of thixotropic glazing-medium, such to produce the desired thinning before application to the painting.]


Concering these finishing palettes, in one particularly-intriguing instance the reseacher variously tested a couple of unknown dark "blobs" found ringing the central transparent medium.. These blobs, which exhibited a dark and almost black appearance macroscopically (and which "...thinned-out to a yellow-orange tint when viewed in thin film on the diamond cell during analysis"), gave-off markers for drying oil and a clay. The author decided these black-ish blobs were likely a sort-of 'bulking-agent' for addition to Durand's colors .


Now, I found this notion of Durand using a bulking-additive a bit odd because, for one, I am unaware of any HRS painters using a "putty medium"; and second, the dark blobs have a very strong coloration. Additionally, as already mentioned, the author reports finding large puddles of Durand's yellowed but clear painting medium still plainly visible within the central area of each of the two palettes. Why might this hold importance? Well, it should be considered, any painting medium placed nakedly upon a palette and without need of a dipper-cup, would necessarily have to be in the form of a paste or a gel; otherwise it would run-off the palette during working use. (I'm also aware that, in time, most gelled mediums eventually slump, which would immitate the eventual puddle-like appearance.) Thus, if Durand's centrally-placed medium was a gel then there would be no further need for a 'bulking' medium ; and so I believe it much-more likely the transparent and black-ish-appearing blobs are Durand's asphaltum oil paint. I will repeat, Durand's typical painted-works show the clear use of asphaltum in their final-glazings. As somewhat further support for my contention, Hartman mentions finding asphaltum paint among the colors in Durand's painting chest, wherein the two palettes were also kept.


Asphaltum contains a very fine ash in its make-up; and it might be this ash-component that supplied the 'clay' finding. Or, perhaps the manufacturer of the asphaltum added some clay to improve asphaltum's usual slumping behavior, though I would really doubt that. Anyway, it would be revealing if a sample derived from the extant asphaltum in Durand's paint-chest were tested to determine if it matched the findings of the various "dark blobs". As I understand it, detecting asphaltum once it has been melted into an oil is exceedingly difficult. Still, it would be revealing if oil and a clay were also found in that tubed asphaltum paint.


James C. Groves

Frostburg, Maryland

November, 2016

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