I'm building up sculptural ceramic pieces using two recipes for vinegar-thickened slip, trailed or spread between layers of paper. I noticed that these thicker recipes can be supported by paper, distorted pretty significantly, and fired almost immediately.
I'm sure there are interesting characteristic forms that emerge from this process that differ slightly from typical casting of liquid clay, dipping and burnout methods, or moist-clay handbuilding. From the conceptual side of things, there are definite similarities to 3D printing, and enough flexibility to keep the spur-of-the-moment manual techniques making contributions, as well.
I wanted to find out several things:
- How tall can the slip trailed stack get before it collapses? (about 7 inches at least, didn't collapse, ran out of paper, got nervous)
- Can the thicker slip hold its shape even when quite fresh? (yes, with minimal help from paper)
- Can I make windows in the walls? (yes, both for the slip trails and the spread walls)
- What range of slip wetness can I still squeeze through the bottle? (thinnest was fresh unchanged slip that was almost too runny; thickest was a loose pudding consistency)
- Will my white casting slip and red casting slip fuse together when I want them to? (yes)
My ultimate goal is to make forms that can be used functionally. I am happy with these quirky early results that I got. Many of the materials will be familiar to ceramics folk, except perhaps for the techniques of putting them together. The tallest or most interesting results are shown first, then followed by more detailed explanations and process photos of those and other trials.
Thinner slip trailed from a squeeze bottle was built up with napkin tissue paper as separating and stabilizing layers. High-tech , eh? And the cheap kind, at that! Thicker slip was spread between layers of newspaper and manipulated into different shapes. Both methods can be combined in the same piece.
This tallest stack with trailed slip (shown below) is about 7 inches tall (give or take). The open space at the top toward the left was a deliberate break in the layers. I was getting toward the end of my supply of cut up napkin squares, and frankly, wanted some excitement. Instead of making a continuous slip line all the way around the square shape, I stopped drawing in the same inch for several layers. The next full path was supported by the napkin layer, so it formed a "bridge" of clay slip. Happily, it is strong enough even after the paper burns away.
Looking closely at the layers individually from the side, I see that the layers from the bottom to the top have different qualities of line. Some lines are more blobby and flattened, and some are thinner and rounder. This is because my squeeze bottle had to be refilled a few times, but I hadn't worked out exactly how much vinegar to add, or how best to add it. Some mixes were runny, some were too thick, and sometimes the bottle simply wasn't mixed thoroughly. But the sculpture never fell over!
Thixotropic clay paste (in white) formed immediately into a simple shape seems promising. Shown here are all the surface details that were captured by the texture and wrinkling of the paper carrier. This texture could easily be removed once the clay is more stable, because there isn't anything new about the clay slip's properties other than the fact that it's more gelatinous when quite wet.
WHAT'S THE BUILDING PROCESS?
Trailed slip lines (shown here, anywhere in this article where the clay is red) were separated by cut-up napkin paper. The paper is very absorbent, a bit stronger when wet than toilet paper is, and easy to cut in stacks with a paper cutter. The clay paste walls (white clay) is spread between layers of newspaper.
In each case, absorbent paper is used as a support. I chose newspaper and napkin paper because they're both easily obtained and folded, and allows these liquid or soft clay mixtures to be manipulated in ways that would typically require more elaborate molds. Usefully, the paper confers minimal texture while preventing many extraneous marks, shrinks as the clay shrinks during drying, and burns off in the kiln.
I'm using two types of paper for two different functions.
- Newspaper: The newspaper is being used for the core structure and main support layer for the frosting-like (thixotropic!) white clay recipe. The resulting white tube shape in this essay is fairly bland, or at least, not the generic shape I really want. I did prove that the newspaper peels off the clay even when the clay is still quite wet. This enabled me to move the laminate around while completely wet, and yet peel a strip off the white clay square and expose it anywhere I needed to join two surfaces together. The wetness of the slip joins perfectly to itself without the need for the typical scoring and slipping process.
- Napkin tissue: The napkin tissue paper is being used as the stabilizing layers for the more organic-style bottle-squeezed layers. The color slip is a darker brown as a contrasting color to the white clay. While I did not explore my guess that the layers do not have to be all horizontal, I can see by the undulating forms I did get that more extreme curves to the slip trailing would most likely hold together as well as flat layers do.
PROCESS DETAIL: Slip Trailing
Here is a series of photographs with details about the slip trailing process using paper napkins as structure. I was inspired by the idea I was taught by my grandfather as a young shaver: put a bit of toilet paper on a bleeding nick to help stop the flow. I wondered all these years later whether it would help the clay set up faster. I think it does!
NAPKIN PREP, or, AM I REALLY USING A PAPER CUTTER TO MAKE NAPKIN LINGUINI???
I cut up many sheets of napkin paper and have them where I can reach them. The outer dimension of the paper sets a limit on how big an outline of slip I can expect to have enough support while wet. The current flowing nature of the slip seems to stabilize when I draw a line no closer than 1/4 inch from the edge.
These thin papers burn off in the kiln with a minimum of ash and will not harm other pieces. There is often legitimate concern that the products of combustion of this extra organic material might cause kiln elements to burn out more quickly. The napkins involved in these tests weighed less than 20 grams. When you compare this to the vaster quantity of organic matter that is burned off from every single clay piece in the kiln already, the increase in risk is negligible. I'm sure someone will provide us all with useful data in this regard.
PREPARATION FOR KILN
I was concerned on one of the early pieces I made using this method, and dutifully tore off as much of the napkin paper as I could without breaking the form. Poor thing looked like a plucked bird, and I can't imagine it was worth my time. These pictured here went into the kiln fully papered.
WHITE CLAY AS PASTE, SPREAD THIN AND MANIPULATED
The photos in this set show the setup of the white clay paste. It was originally intended to be dried in a pleated shape, while being held by the metal bending former. It almost worked, but it failed in an uninteresting way, so I scrapped the pleating idea and used the clay panel as a tube instead.
WHITE CLAY AS PASTE, SQUASH-FORMED: Faster, yes? Better, maybe!
After finding out what happened when I spread the paste manually, I wanted to see if there were a faster way. For smaller amounts of slip, it turns out there is a faster way: simply squash it. This probably has a minimum thinness due to friction and how much pressure can be brought to bear on the simple materials used here. But if scaled up, with smoother and stronger paper, harder and flatter boards, and mechanical assist for pressure, I could make much larger membranes as laminates in a way that might be more convenient than spreading. Might not.
COMBINATION OF PASTE AND TRAILED METHODS
An important aspect of these methods is that the trailing recipe and the paste recipe adhere to each other easily. I found that it does. The white column form with the red base was the first attempt and gave good results.
- Paste or Frosting-like clay slip: About two tablespoons per cup of slip, stirred really well. Add a little more for thicker paste, add a little water for thinner slip. Adding unaltered clay slip seemed to affect it less than adding plain water did.
- For slip trailing (that will still comfortably pass through a squeeze bottle tip): a few drops of vinegar per cup of slip. Be careful adding vinegar in minute amounts. A consistency you can still squeeze through the bottle gets inconveniently thick very easily.
Should you, or could you, make these slips from your existing moist throwing body? You can, but it's an amount of work people cringe at the thought of doing. If you need the moist clay and slip clay to match, then you must do it. It will be a bit less work if you start from your mushy recycled bucket because it's already fairly wet. The difference is only slight between the recipe for the familiar moist clay from bags, and a clay slip that can be fluid enough to squeeze through nozzles. Many good explainer articles provide varying levels of detail on how to mix up soft clay pastes like these from different starting points.
The stiffest recipes I used started from already-dense casting slip, and could be shaped like cake frosting. The basic components are dry clay powder, water, and chemicals that act as suspension and flow helpers (called deflocculants). For myself, I have used casting slip which is already fluid, and added a little vinegar to it which makes it slightly more syrupy to keep it from sagging when I'm laying out lines.
SQUEEZE BOTTLE PROBLEMS
I realized the awkward way that the slip consistency plays a big role in how controlled the forms appear. For the pieces shown in this essay, I had a fair amount of control over the consistency, but there's clearly room for better protocols. I was impatient and often got globby slip, but at least I know what to do when I want slip that won't squeeze out of the bottle evenly!
Just a bit of helpful advice: Mix your slip first in a wide container with a whisk or heavy flat utensil, before putting it into your squeeze bottle. I made the regrettable choice of adding vinegar to the squeeze bottle directly, thinking "Oh, I'll just shake it up." It mostly works, but not really.
WHY BOTHER WITH ANY OF THIS? WHY USE SMELLY SLIP WHEN HANDBUILDING PROCESSES ALREADY EXIST?
Okay, I'm already being a bit facetious: The clay slip thickened with vinegar doesn't really smell much. I've heard that these mixtures might spoil over time, but mine so far are okay.
From and engineering and artistic perspective, there's already a great deal of work using liquid slip as casting material and thicker slip as a drawing medium. To add to that body of work, I'm using paper as non-typical shaping methods for the thickest versions of the slip recipes. Using this paper-clay-paper laminate, I'm exploring the methods needed to make functional pieces or sculptural objects in ways that could scale up to many dozens of pieces. Plus, it's fun and the resulting forms happen fast. These methods have the incremental-slice methodology of digital 3D printing, but also retain some of the analog hand variations possible with sculpting. Since it's a mix of processes, at the moment I'm calling it "hand-printing."
From a visceral standpoint, I do wonder if something is missing from the process when we don't touch clay directly. Touching the familiar form of clay holds a great satisfaction for so many people. Soft clay seems to invite the most direct approach of the hand, and records all actions upon it. We make our mark on the blended, soft and moldable stuff from store-bought bags. We wrestle and thrash with the hard-won, rocky, grainy, often sticky piles of it found outdoors near bodies of water. Is there anyone who hasn't touched clay at some point?
But, that said, for those of us who are as likely to draw as sculpt, or build instead of sculpt, what can clay do? Maybe something like these things I'm exploring here.
THE SKY'S THE LIMIT.... ALMOST
- Larger abstract forms with more than one interior wall
- Changing the orientation of the growing pile so that the layer direction changes
- Getting significantly different diameter nozzles, so that a layer might have one huge strand or several smaller strands, all combining to become the structural wall
- Pleated surfaces that are mounted in frames as wall decoration
- Slip trailing as typically used for decoration printed onto newspaper just prior to spreading the thicker structural slip, so that after distortion, the surface is already patterned
Thanks for looking at the pictures, and bonus thanks for reading. This is a small beginning. Let me know what made sense and even better, what didn't make sense.