First firing

The first two umbrellas were fired last weekend and came out of the kiln on Monday. The temperature we had agreed on trying, due to dangers of warping and cracking, was 1240 degrees Celsius, 10-15 degrees lower than the previous tests of smaller works. As mostly the case when opening the kiln, I was slightly disappointed: the surfaces looked rougher than they were when going in the kiln, as if the porcelain was under-fired. This turned out not being the case; they are perfectly vitreous; unless being put side side by side with the same material fired to a higher temperature, one does not notice the difference. Most importantly, there was no warping and cracking in the kiln. Which is a significant and most welcome outcome, but one that was completely undermined by the fact that the surfaces showed up every imperfection, the entire history of the construction of the piece in the most unflattering way. Patch to cover the drain whole on the bottom? Was invisible before the firing, but now it clearly shows. The place where the two mold parts come together? There is a shallow but clearly visible indentation running around on the inside, looming with a dark shadow in the sparkly whiteness of the clay. The surface was sanded and polished before it went in, it came out with ghosts of every brush- and knife-mark I've ever made. Unforgiving material.
It took me a while to get over this... Reassessing my feelings during repeated visits from every staff member and fellow resident helped me to fume out my disappointment. I reasoned that I was prepared for things happening in the kiln but not for these kinds. Instead of interesting slumping and warping that would have fit into the original idea, this new development only made the work that I had labored over so much look like that it had craft issues. But come to think of it, it's good to know that bone china behaves likes this, and now the next challenge is to change the designs and maybe the process too, in order to make the work in such a way that what cannot be made invisible at least does not become the focus.

Last Sunday, we went to Antwerp (Rubens' had his studio here) to look at some paintings, eat chocolate and drink beer. Mission accomplished. Two beautiful paintings stuck in my mind, both both Madonna with the Child, from the 15th century. This one, by Fouquet, shows her as if she was made out of rubber and inflated.

And now, the fun part...

By now, every step of the casting process had come together and with that a weekly rhythm of work has been formed. Not surprisingly it takes more time than I expected; it would be difficult to get more than two umbrellas finished in one week. I cast on Monday and take out both pieces by Tuesday. The studio, which used to feel spacious is crowded with molds, drying pieces on kiln shelves,wet pieces I'm still working on under plastic tents, and the barrels and equipment that hold and move the slip. Here is a picture of The Awesome mold with the lift that had raised the piece up still inside right after removing the cast from it.
Tuesday and Wednesday, I work on putting the design into the umbrellas. Each has a map of a real place, a city or a neighborhood, a path or an area that I run around in. This is another time-sensitive part of the process: the designs are done as a shellac resist, wiping away the clay from the areas around the resist pattern with a wet sponge. It takes a few hours of wiping to get the depth I need, and it is the safest to do this while the porcelain is still wet so that it does not crack from the sudden expansion when water is introduced.
The rest of the week is spent on carving, and more carving, and still more carving... and cleaning the designs. Also on doing odd tasks, like cleaning molds, rearranging furniture, finalizing the new templates for the maps to be carved next, building firing molds, etc., which are necessary but always feel like as if I was not doing anything. The carving part is where I can relax and go with the flow... It is fun to trace the street patterns of familiar places but also to get lost in them. Repetitive? No problem.
Fridays, it looks like, will be the days to load the kiln and start the firing. The first went in yesterday. Being a test, I trying my best to keep my expectations low. I'd like to fire the bone china to full maturity (about 1240-1250 degrees Celsius) but it is guaranteed to warp, slump, crack or just plain self-destruct at these high temperatures. These first pieces went in on a bed of sand. Probably insufficient as a support... A firing mold might be a safer solution, but first I need to see what happens in the current firing. The idea started with a discarded, broken umbrella that I found. It would work just fine if the kiln (gently!) did the same for the sculptures. After all, there has to be a good reason why I'm doing this in clay and not some other, more direct and less technically involved material!

Castings

The very first cast got taken out of the mold only on Monday. I did not really have any choice but to wait; I had to get the right materials for the harness at the Saturday market and wait for assistance with flipping the molds when the staff came to work after the weekend. The technology I came up with at the end of last week worked as expected. The de-molding has to happen in two steps: Step one is flipping the cast with the mold still on onto a board (needs lots of foam to pad the dome from the inside in order to prevent collapsing) and lifting the mold away. Drying does not improve the strength of this clay, in fact, makes it even more susceptible to cracks. Unfortunately, an umbrella is not really a half-sphere but a dome that stands on 8 points. One of them gave in to the stress and went cracking along when the cast landed on the board. By the minute the crack grew, opening up a sizable gap along one of the ribs. The cast was relatively clean but the edges still needed attending and with each touch the gash got visibly larger. In step two, the cast was strapped down to the board with 4 strips of fabric and flipped upside down, hanging in this harness-like structure. Two of us lowered it into a pre-prepared sandpit on the kilnshelf and two people cut the straps to get the board off. It worked like a charm. Only that the crack did not hold up (I no longer expected it...) and went straight for the opposite end, splitting the form into two equal halves. It was a huge disappointment! I expected that I would not get away with it (the first casts from any mold are usually not very good), but I still hoped that my luck would hold.
The other residents who helped me with the flipping walked away quietly and tactfully, and I felt as broken as the cast was. For only a few minutes though...
Then, I cleaned up, recycled the clay (it's better for this to happen now than in the firing!), rearranged the space to make room for casting again next day and walked out of the studio.
On Tuesday, I cast both molds. The process is unbelievably exhausting; remixing of 75L of slip, pushing barrels up and down in my studio, moving them with the forklifts took the entire day. This time, I wanted to try casting into the one-piece mold differently: a thin shell was cast first then the ribs got reinforced with gauze, then more slip was brushed on and burnished flat and even. That same night we repeated the flipping process with the harness, and this time it worked flawlessly. No cracks, no damage, the form came out pristine and beautiful.
Removing the cast from the other mold (The Awesome) required a bit of thinking, and trial and error, which took up most of the day on Wednesday. The bottom of the mold was unbolted and dropped down, exposing the bare bum of the cast. Then, a lift was set up with a columnar structure built of bricks, which was narrow enough to fit through the opening but still large enough to support the bottom of the piece. Using that to levitate the piece out of the mold, the rest of the mold was dropped down too. It kind of looked like a flower emerging. Pretty cool!
The only thing left to do is to put my hands under the form and gently cradling move it to the sandbed on the kilnshelf. Surprisingly, it worked. Now, both casts are resting a slowly drying under a plastinc tent.
Of course many things can still happen during the drying and, especially, during the firing. But the first challenges are considered to be solved.
My color tests came out amazing. Thin lines of color on smooth vitrified china. I'm in love.

The Monster, The Princess, and The Awesome

I have three molds of the same form now. One has to work. If I'm lucky, two will work.
The first one, which made me so excited last week (a.k.a. The Monster) is no awaiting to be carried out to the dumpster. It turned out not very useful for casting as the multiple parts made the fitting back together complicated and also unstable once one part is removed. The edges of each part lost definition due to the parts moving and rubbing together in this unstable fit.
The flaring out shape of the upside down umbrella creates a number of complications; turned over to be a dome rests the entire piece on the 8 ends of the ribs, risking stress fracturing. It's a no win situation. Somewhere between casting and removing from the mold to a kiln shelf there is a minefield of challenges to overcome. So, to test some theories and see the potential outcomes I made two more molds early this week; a one-part (The Princess, - she is a beauty!) and a two part (The Ultimate, a.k.a. The Awesome). Of course, each have an additional casting ring added to the body of the mold. It may seem like a waste of my time, considering that the first one took 4 days to make and ended up unpractical, but without making that first I would have never figured out what was needed to be done.
On Thursday, with the generous help of a staff member, Mark, I set up the casting system. The mold takes 50Liters of casting slip. That is about 80kg (160lbs). In bone china, that is about 200 Euros worth of raw material, by the way. It was important that the system was simple (only the necessary steps), foolproof (the mold won't tip or break under the weight), efficient (no loss of casting slip and no heavy lifting) and could be managed by me, on my own. For an entire day we were testing possibilities and trouble shooting. By the end, we arrived to a functional set up of two pallet lifts and a 60L barrel with heavy duty plumbing.
The mold was leveled and in went the 50L of slip. It took my breath watching it flow in, so creamy smooth and slow; it seemed not to rise in the mold at all, just sitting still. We poked at the edges, excitedly taking out test samples of the wall to judge the amount of buildup. Fishing in a huge pool of liquid light gray silk... When we opened the drain on the bottom of the mold to let the slip out, it went gushing back to the barrel, making a cute "belly-button" vortex in the middle of it. It was beautiful. Almost more interesting than the sculpture that it makes can ever be.
The next day, today, the new challenge is to take out the cast form the mold. Being a one-piece, the only option is turn the mold upside down and de-mold the cast, similar to kids making sandcastles on the beach. Except for the exceptional fragility of this particular material. Any pressure at a single point or surface will make it crack and break. We brainstormed through many options with Peter and each seemed to be too risky. At the end we settled on a sling-type construction that will be put on once the cast is flipped to the board, then the whole thing turned upside down the sling hopefully cradling the piece evenly. We will put the theory to the test on Monday. In the meantime, I have lots of thinking and testing to do with regard to the maps that will be carved inside the umbrellas' bowls.