by Dick Lehman
I can hardly remember a single occasion during the past 20 years of
my pot-making that I haven't cringed and grimaced as least inwardly
at the repeated requests from customers to "deface" my pots.
What does Aunt Tillie's birthday, Fred and Jean's anniversary or, would
you believe, "Best-of-Show" goat breed have to do with my artistic statement?
Most of us who work with clay inevitably, incessantly receive these
requests to personalize our ware for the perceived needs of our customers.
If you are quiet, and really concentrate while putting your ear to
a ball of clay, you'll likely hear the corporate baleful moan echoing
from the generations of potters who have tried, each in their own way,
to answer these thorny requests with integrity and respect. Potters
and clay artists have taken up residence at every conceivable point
along the spectrum of responses. Some have said "yes," and embraced
the opportunity as part of customer service, financial security and
niche marketing. Others have taken these petitions on as a design-integrity
challenge. Still others have hoped against hope that in servicing these
kitsch-prone pleas, the integrity of well-made, handmade pots would
overtake their customers with such power and vision that they would
know better than to ever ask again.
Some have compromised their better judgment and complied almost against
their will, perhaps to please Aunt Sally or Grandma Mabel. Some have
turned customers away with a wince: "Sorry, I just don't do those kind
of things." Others haven't been so kind.
Although I still cringe and grimace, my spot along the personalizing
spectrum has largely been one of trying to respond positively to my
customer, if I can. I maintain a sense of hopeful naivete, trusting
that with a little gentle nudging, maybe next year my customer will
conclude that Aunt Thelma will remember her own name and her own birthday
without having it splashed across one more mug. I hope I might be convincing
when I suggest to my customer that the gift may be as-well (or better)
received if the important names, dates and particulars show up on the
bottom of the pot (if at all), instead of emblazoned across the side
in billboard fashion. And I hope that business folks will see it as
a progressive suggestion when I remind them that their employees will
remember where they work and are not in need of being reminded; that
loyal customers may prefer a well-made pot over an alleged gift of thanks
that has been turned into a self-serving advertisement.
Still, in the face of all my gentle nudging, some people need products
that are personalized. They need them because, well, they just do! Businesses,
schools, corporations, clubs and churches have need of products that
advertise, recognize, promote, and symbolize. Nothing I say will ever
change that, nor in reality, would I want to. For these important occasions
and promotions, I do prefer that these folks choose handmade products
rather than commercial slip-cast ware.
So it is that I am always on the lookout for better, classier, less
obtrusive ways of including personalized information on products. I
have tried many of the processes that many other potters have tried,
including drawing, painting, silk screening (see the CM portfolio "Freedom
to Experiment" by Les Lawrence, April 1993; and the CM article "Silk
Screening Slips" by Marvin Bartel, March 1973); stamping greenware and
filling with oxides (see "Stamping Made All the Differencne" by Jasper
Bond in the May 1988 CM); stamping followed by glazing, which accentuates
the calculated irregularities of the impression; and decals (see CM's
two-part article "Making Ceramic Decals" by Jonathan Kaplan, April and
May 1975). Recently I discovered another avenue that may be of use to
others in the clay community: laser engraving high-fired pots.
While talking to a friend who regularly has a considerable amount of
wood products laser engraved, I wondered aloud about the potential effects
of a laser on a fired glaze. She offered to take several pots with her
to the engraver. Of the two samples I sent, the results were quite different.
The opaque white glaze was simply etched, and the engraved area barely
visible. But the glossy green glaze had a distinct bronze color wherever
the laser had engraved and re-melted the surface. Within a week I had
tested all my glazes. I discovered that five of them responded with
color change when the laser engraved the surface.
When I began investigating this process, I knew little about lasers.
I know only a little more now. But here are a few things to describe
the process in broad strokes. Laser engraving is accomplished by using
a beam of ultraviolet light, concentrated to a point approximately 0.006
inches in diameter. Most of us have probably seen wood items with intricately
engraved designs. Other common applications in industry and manufacturing
include laser-engraved designs on glass, acrylic, leather, painted metal,
and anodized aluminum.
The pulse and intensity of the ultraviolet beam can be controlled by
a computer. Many systems use standard graphics software such as Corel-DRAW!
or GeneriCADD to provide both control and flexibility in type styles
and engraved images. Existing computer (digital) images can be incorporated
into the engraving as well. Camera-ready art, hard-edged graphics, even
photographs can also be scanned into the computer for engraving.
The laser beam moves in a raster and/or vector mode to produce the
image, while the "workpiece" (pot) says stationary. The machine I utilize
accommodates a maximum workpiece of 11 ½ by 17 inches, with a maximum
workpiece thickness of 7 inches. Because the laser must be focused in
much the same way that one might focus a photographic enlarger, relatively
flat products (tiles, plates or platters) present less challenge than
cylindrical objects (mugs or pitchers). To accommodate the curve of
a mug laid on its side, the effective engraving area is limited to approximately
1 ½ x 1 ½ inches before the laser is "out of focus" to the extent that
it no longer affects the surface of the glaze. For cylindrical forms
to be engraved across a broader area, the piece would need to be repeatedly
rotated while maintaining some registration.
A very recent development in laser tool design is the production of
a chuck-like device, which will center a symmetrical cylindrical object
and turn the object while a stationary laser head pulses. This additional
technology will allow, in theory, for cylindrical forms to have full
360-degree images printed. (I have not yet had access to this tool in
But what actually happens to the surface of a glazed piece during laser
engraving? And why do some glazes "work" while others do not?
A laser expert, a physicist and a chemist would each likely give us
different answers to these questions answers we eventually should
explore. Unfortunately, I am none of the above. But let me tell you
what I do know, and about some of the observations that I have made.
On high-fired (Cone 9-10) reduction glazes, the surface of the glaze
is always etched by the laser. That is to say, some of the surface material
has been removed by the laser. If you rub your fingers across the surface
of the glaze, you can just barely feel the contours of what you are
If you watch the laser operate, you will see pulses of white light
at the intersection of the laser beam and the glaze. I have been assuming,
based on the color of the heat that is generated (white), that the surface
of the glaze, in addition to being partially removed, is being re-melted
in a strictly localized area. (More on melting and fusion later.)
Light-tone matt surfaces, and especially glazes with rutile as a major
colorant (4%-8%) seem most "color responsive" to the engraving process.
Gold glazes change to bronze, pinks to dark mauve, light blue changes
to dark blue. Two of the recipes listed in my CM article "Stealing
Ideas," June/July/August 1993, work well: Rhodes 32 with Rutile
and 2-D Blue. One of the gloss glazes (Mark's Special Glaze) in the
same article is most striking, changing color from a glossy "seafoam
green" to a rich, deep matt bronze in the engraved areas.
I would pass along one word of caution regarding the use of a laser
on glazes that have significant crazing (as fluid glossy glazes sometimes
do). Be sure to do some post-engraving testing of the surface to see
if the glaze retains its integrity. Since the laser disrupts the surface
tension, and actually removes some glaze material, badly crazed glazes
may chip away or fleck off at the edge of the engraved areas. (The post-engraving
testing is, of course, recommended for all glazes, but especially for
any with crazed surfaces.)
In my experience, white and very light-colored glazes with glossy,
satin or matt surfaces are etched at the points of engraving, but there
is no color change in the glaze. Likewise, iron-saturated glazes like
traditional temmokus experience a textural change at the point of the
etching, but no perceptible color change. Glazes whose colorants are
predominantly cobalt or chrome act similarly, regardless of surface.
(Obviously, the matt texture of the engraved area is a bit more noticeable
in contrast to a glossy-surfaced glaze than when the glaze has a matt
or satin surface.)
Assuming that the glaze re-melts during the heat response of the engraving
process, I wondered if the laser would melt a raw glaze and fuse it
to the pot. I tried a normal dipping application of a temmoku glaze
on a bisqued pot. (I regulate the specific gravity of our glazes by
always checking with a hydrometer.) As the laser engraved the raw-glazed
surface, the affected glaze changed from the brick red to the expected
shiny chocolate brown. A visual check with a high-power magnifier, prior
to touching the surface, revealed that the glaze had indeed melted and
was fused all along the route of the laser. Touching the fused area,
however, brushed it right off the pot. Only the surface layer of the
raw glaze had melted.
Our normal application process had created too thick a coating of glaze
for the laser to melt completely, so there was no fusion to the bisqued
clay. Increasing the laser pulse and intensity, then repeatedly addressing
the same surface area did seem to increase the mass of melted glaze,
but did not fuse it to the clay.
I suspect that with careful monitoring it would be possible to regulate
a glazing process that would apply just the right thickness to the pot's
surface so that the laser would both melt and fuse the glaze to the
clay. My hunch, based on my limited experience to date, is that the
amount of glaze needed would be very small, and that traditional dip
glazing would not fulfill the uniformity-of-application requirements.
(Variations in the porosity of the bisqueware would also have a major
impact on any dipped glaze application.)
One can, however, dream further. If one solves the application problems
and it becomes possible to fire and fuse a glaze onto a bisqued pot,
one could theoretically make repeated applications of different color
glazes (washing away the unfused raw glaze after each step). With some
registration procedure, it would create a kind of color "fusion-printing"
process using fired glazes in almost limitless detail.
I have also tried staining bisqued pots with a light iron oxide was
prior to subjecting it to the laser. The minute amount of iron oxide
on the bisqued surface is removed in the laser engraving process (along
with a bit of the pot), leaving unstained areas on a stained "background."
Firing these pieces produces a light image on a dark background. Here,
the laser "cuts" through the printing medium and the printing medium
is removed, providing yet one more way of using the process.
I can think of a number of other approaches to the "fusion-printing"
style that might be pursued. One might brush liquid high-fired glazes
or a liquid high-fire stain over a previously-glazed and high-fired
pot to see if one could more easily monitor the thickness of application
on a nonabsorbent surface. The raw stain/glaze could then be engraved/fused,
and the unaffected areas washed away.
One might also try applying liquid low-fire glazes or lusters over
previouly-glazed, high-fired pots. The relatively high predictability
of color with low-fired glazes (and potentially lower fusion temperatures)
might make this just the right medium for laser etching, if the application
and fusion problems can be solved. I think it is worth a try.
I have almost as many questions as I have experience-based answers
regarding this process. The possibilities are quite expansive. I trust
that you will humor my forwarding some of these ideas prior to thorough
testing. While I have interest in all these possibilities, if one waited
to share this information until all potentialities are explored, many
others who may be interested in the process would miss the opportunity
to join in the exploration and share in the discoveries.
It is equally obvious that I have explored only the more commercial
applications of the parts of the process that I do understand. Of course,
one need not avoid using laser engraving simply because it has commercial
applications. Potters have always co-opted all sorts of commercial applications
for artistic ends. Witness the innovative use of decals, silk screening,
monoprinting and stamping. This laser information may be just one more
instrument you store in your toolbox of resources.
This article is reprinted with expressed permission from
the January 1995 issue of Ceramics Monthly Magazine, PO Box 6102, Westerville
OH 43086-6102, USA; www.ceramicsmonthly.org
© Dick Lehman, 1995. All rights reserved.