Carbon-Film-Transfer in Saggar-Fired Porcelains
by Dick Lehman
Many year ago I discovered, in an accident of American Raku firing,
that fresh leaves and grasses can, under the right conditions, create
vegetation images on hot pots: During an all-day firing marathon,
a storm blew up unexpectedly. The tornado-force-winds arrived so quickly
that I didnt have time to stop the firing which was in process.
I had just pulled a large bottle out of the kiln, had flamed it in sawdust,
and covered it with a metal garbage can. Fierce gusts of wind unexpectedly
blew the trash-can half a block away, and the still-thousand-degree
bottle rolled down a dirt embankment, through some grasses and came
to rest against a fence post. To say that the retrieval of both the
cover and the pot was "spirited", would be to understate the
duress of the moment. However when the resultant cooling had taken
place, I discovered to my amazement that the pot retained images on
the copper-stained surface from the grasses through which it had rolled.
Not wanting to abandon this fortuitous event, I continued to fire in
the waning wind, hoping to possibly replicate the "accident"
by placing the very next fresh-from-the-kiln copper-stained pot on its
side, atop a mound of sawdust covered with freshly picked sumac leaves. Twenty
minutes later I had my first successful follow-up piece: a lovely soft
likeness of the sumac appeared as an image in the copper stain, on the
side of the pot. And subsequent firings yielded only successes as I
pursued this method.
Several years later I abandoned my pursuit of American Raku as I had
known it disillusioned by the fading/re-oxidizing surfaces of
the copper stain. The once-brilliant colors, after several years, became
drab and muted, much to my disappointment and to that of my customers.
Not having found a solution to the problem, I discontinued marketing
these pieces. It was a hard decision: I loved the vivid images of vegetation
against the serendipitous variation of the Raku coloring.
I began to look for some other method of firing which might capture,
on the same piece, the magic blend of spontaneity and explicit detail. Somehow
I intuitively moved toward saggar firing.
Looking back, I conclude that it was an unlikely leap of logic which
caused me to assume that saggar firing would be the answer: that saggar
firing would somehow capture the explicit detail of fresh vegetation
pressed against pots, while still offering unpredictable spontaneous
And it was likely one of those acts of grace or good fortune, which
occasionally enter each of our lives, which caused the startlingly successful
results in my first veggie-saggar attempt: wonderfully
explicit images of fresh vegetation dancing in and through the seemingly
celestial/astronomical patterning which blessed the rest
of the pots surfaces.
I say, "good fortune/grace", because for the next several
hundred pieces I fired, there were no successes at all! Oh yes, the
pieces had some successful saggar-fired markings, but no explicit imagery
from the vegetation at all.
Perhaps it was a healthy state of denial which caused me
to keep trying, in the face of relentless failure ("Surely it will
happen again if I just work hard enough."); perhaps it was my life-long
interest in landscape photography my passion for images which were
close up, which revealed explicit and intimate detail (like those made
by Paul Caponigro and Arthur Lazar) that spurred me on; perhaps it
was the too-easy transition from tornado-accident to regular successes
in the veggie-raku realm that caused me to remain stubbornly
It was an odd and curious experience to have these several (original)
very beautiful veggie-saggar pieces (which I had made) in front
of me on my desk each day pots with delightfully-delicate imagery,
pots with such explicit detail that I could see the veins and tears
and worm holes in many of the leaves; pots which were the ceramic counterparts
to the contact prints which I routinely made from my 4x5 negatives in
the darkroom; pots which had seemed so easy to produce in my very first
attempt and at the same time to be continually, perpetually, interminably
failing in each attempt to produce any more of them.
I continued to investigate this mysterious process, but I was not able
to explore it in a full-time manner. (I was producing and supervising
in a full-time production studio while this pursuit was in motion.)
So the loss of several hundred pots covered a period of about a year
and a half. Each unsuccessful unloading had me scratching my head,
writing more notes about procedural decisions I had made in that
particular firing, and comparing my results with the pieces on the desk.
If ever a character defect was an artistic advantage, perhaps my stubbornness
was, in this case. Unable to repeat the accomplishment of the first
firing, but also unable to believe that I couldnt do it
again, I kept trying. And eventually after a year and a half, I did
finally begin to see at least occasional results which lived up to
my best hopes.
I now know that the devil is in the details. After ten years of practicing
this firing method, I have concluded that these are the variables to
which I must pay attention, and which ultimately make a difference in
the successes (or failures) of the firings: a) sawdust particle size,
b) the amount of sawdust in the saggars, c) the type, thickness, substance
and placement of the vegetation, d) the firing temperature, e) the kind
of kiln in which the saggar is fired, f) the kind of saggar used, g)
the manner in which the saggar is sealed, h) the length of time the
saggar is cooled, and i) the manner in which all of these variables
work together. It was only after paying close attention to these variables,
and their interrelatedness, that I discovered what I had so blithely
(and fortunately) stumbled upon in that first successful firing. However
even now, more than ten years later, the best results are sparingly
attained and seem elusive. With the success rate for the best works
at far less than 20%, Ive needed to develop a tolerance for more
failures than successes.
Here is a general explanation of how I am now firing for the results
which are shown in the photos which accompany this article: A saggar
is partially filled with 5 inches of fine sawdust. The pot is laid
sideways onto the sawdust and pressed down to create a "nest"
in the sawdust. The pot is removed, and fresh vegetation is placed
into the nest, and the pot is put back in place (on its side) on top
of the vegetation.
Next, more vegetation is placed onto the exposed top side of the pot.
It is then covered by an additional 5 inches of fine sawdust. The saggar
is then lidded.
During firing, an anaerobic atmosphere develops inside the lidded saggar. The
vegetation turns into "activated charcoal" and in the process,
releases a film of carbon. The bisqued porcelain, being porous, absorbs
the film of carbon, capturing the image released from the vegetation.
This speeded-up process mimics, according to the paleontologists to
whom I have spoken, the much-slower fossil-formation process called
"carbonization" or "carbon-film-transfer" (which,
in nature, causes volatile materials such as nitrogen and oxygen to
be squeezed out of vegetation, and chemical action changes the tissues
of the vegetation into a thin film of carbon. What remains is a residue
forming an outline of a portion of the previously living leaves. If
thick accumulations of plants derived from swampy coastal lagoons or
deltas are carbonized more completely, coal deposits may develop).
Because the saggar maintains a relatively anaerobic atmosphere (no
oxygen), the vegetation does not burn (and instead becomes activated
charcoal), and is still present after the firing is completed (albeit
in a black, shrunken form of charcoal). The anaerobic atmosphere also
explains why the carbon image on the pot is not burned away: red-heat
temperatures would "perceive" the carbon in the image as a
fuel, and burn it off the pot if oxygen were present to complete the
Very slight air leaks in the lid of the saggar may cause white areas
on the surface of the pot to occur (in these cases, carbon is
burned away). Careful control of the particle size and depth of the
sawdust can lend a bit of mastery over the light and dark areas
allowing one to dictate whether the carbon images read as "negatives"
or "positives," and adding to the sense of the miraculous
which sometimes attends these surfaces.
A final word about the "miraculous": the paleontologists
with whom I have spoken have referred (when speaking about fossils)
to the "miracle" of preservation, due to the vulnerability
of organisms to decay and destruction after death (and the resulting
potential loss of record of many individuals or even entire
species). Recently a combustion chemist visited my studio
and expressed a similar perspective regarding the unlikelihood of consistently
creating these "fast fossils" (due in large part to the near-endless
number of variables at work in simple cellulose combustion
Something about the unlikelihood of this process, and its elusiveness
are an attraction to me. It is an arena in which there is much to learn: one
could choose to take a paleontological or combustion chemistry approach
in an attempt to discover what is actually happening in the process. And
such learnings would, no doubt, offer some keys to additional methods
of control (and perhaps successes) in what is otherwise a rather capricious
And there is much to master simply through the continued practice of
the firing process (regardless of what one understands of the paleontological
or combustion-chemistry implications of the method). Careful observation
and documentation of ones decisions will continue to yield tools
which may offer a little more control.
However the inherent lack of control which will always accompany this
approach to firing and surface articulation is also what contributes
to some of its most amazing successes. I believe that the process
produces results which are far superior to anything which I might make,
if I did control most or all of the variables. In that respect,
this approach, while full of loss and disappointment, is also full of
wonder and surprise an approach which transforms me into as much
a "receiver" of these works, as a "maker" of them.
It is, in part, this mystery which propels me to continue on with this
Dick Lehman is a frequent contributor to Ceramics Monthly
magazine, and maintains a full-time studio and gallery in Goshen, Indiana.
This article is reprinted with expressed permission from
Ceramics Monthly Magazine, PO Box 6102, Westerville OH 43086-6102, USA;
© Dick Lehman, 1998. All rights reserved.