April Goals

I was back at it (again) in the studio this week. I'm to the point now that I need to see if I can establish some sort of regular schedule again. I've set a goal of two nights a week for now.

The first night was mainly experimentation. Finding out just how out of shape I am, where my skills are at, that sort of thing.  I threw 2 pieces in a little over an hour. I'm a rather slow thrower, so that wasn't terribly bad. Then I cut them down the middle to look at wall thickness, bottom, etc. They actually weren't too bad, considering I'd used the clay thats been in the bag for 3-4 months and was almost too stiff to be usable. I'd wedged some water back in, but it was still pretty bad.

The second night, new clay.  World of difference.  Actually made a couple pieces that might see the kiln.

I have some terra sig that I started in January in the garage that needs some attention. It's been settled and siphoned once, and been setting ever since. Since it's settled, I think I might try siphoning off some of the top water to shortcut the evaporation/concentration a bit. Then I want to see what it does on my pots.

Dorodango!

I'd come across this a couple years ago and it just resurfaced again last week on one of my favorite shows, MythBusters.

A common childhood pastime in Japan is making hikaru dorodango, or 'shiny mud balls' by taking a ball of mud and squeezing, packing and smoothing it, gradually drying it out, and slowly adding dry dirt to it, and finally rubbing it to a glossy shine.

The results are nothing short of amazing.

Looking at the process, it seems like what they're ending up with is a packed, smooth ball finished with an outer layer of finely burnished clay particles, probably not far from terra sig.

Image from: http://www.kyokyo-u.ac.jp/youkyou/4/english4.htm , which also has instructions for making one of these little gems.

There is additional information and instructions here:

http://www.dorodango.com/about.html

and at Wikipedia here:

http://en.wikipedia.org/wiki/Dorodango

Notes on terra sig - part 3

So where am I headed from here?
Being on injured reserve these days, I have plenty of time to think.

What my experiments have shown me is that I definitely want to explore this direction further, maybe take it somewhere no one else has. I've already had some happy accidents with streaking, I'm wondering what else is waiting out there.

For starters, I want to go ahead now and get some proper equipment and materials and see if I can make an even better terra sig using Vince Pitelka's instructions.

I've been using sig on my saggar pieces, and I really like them that way. I'd also like to try it on raked raku, although I've heard mixed results of getting the resist slip to adhere properly to a smoothly burnished pot.

The high shine of low-fired sig is lost when the pot is fired up to stoneware temps, but I want to experiment with that anyway. The more satin finish might be just what I'm looking for.

Notes on terra sig - part 2

In part 1, I talked a little about proportions of clay and water and basic clay prep.

Deflocculants will definitely improve your results over mixing only clay and water. What they do is help separate all the individual clay particles and keep the smaller particles of clay suspended until the larger particles settle out. What to use is a whole other matter.

By far, the most recommended deflocculant for terra sig is sodium silicate. It's very effective, and only a few drops are needed. Other choices include soda ash and tri-sodium phosphate (TSP).
For my first experiments, I used TSP since it was readily available at the local building store as a cleaning agent. Make sure you get actual TSP, and not TSP substitute. I used about a teaspoonful in a gallon or so of slip and it was plenty. Later I used about a tablespoonful in a 3 gallon batch of red sig slip.

So then you mix well - I used a paint mixer attachment on an electric drill for a few minutes.
Depending on the clay you'll usually see an almost oily appearance to the surface when you stop stirring from the fine clay on top of the water.

Then walk away. Let it sit. 24 hours minimum. My first try didn't sem to be separating into distinct layers, so I let it sit for 3 days.

You'll either get layers or not, but either way you'll then want to carefuly siphon off either the top 2 layers, leaving the heavy third layer behind, or siphon off the top 1/2 to 2/3 of the liquid if there isn't distinct layering. This is the terra sig you've been after.

You'll need to experiment with the consistancy. As I said earlier, my first batch used WAY too much water, so I had to evaporate some of the water away to get a usable product. I actually poured it into an old bisque bowl I had laying around which let it evaporate and also absorbed and wicked away water through the bowl.

Next time - Future testing

Notes on terra sig - part 1

I've been looking at all my various notes on all the variations of terra sig. I thought I could put it all together and maybe make sense of it all.

Up to this point, I've just been trying to see what kind of results I could get without a whole lot of trouble, gram scales, deflocculants, and measuring specific gravities. I think I did pretty well, I even surprised myself a bit on my first tries I suppose. But comparing notes, and sitting down and doing a bit of calculation and comparison, I probably could have done a bit better.

This first time, I used about 2 pounds of dry clay to a gallon of water. From what I'm looking at, that's probably way too much water to start. It made the slip easier to mix, but was probably overkill and all that water has to be evaporated back off. The trend I'm seeing is something more like a little less than 1 cup water for every 100 g dry clay. What I used was 16 cups to 1000 g, it should have been about 10 c.

And do yourself a favor, use dry clay, it will mix a lot easier. I busted up some scrap throwing clay in a heavy bag with a big hammer. Don't do it in the open, because 1) you REALLY don't want to breath that fine dust, and 2) that fine dust is actually what you're after, so don't waste it.
If your clay is still moist, just use a sur-form tool or cheese grater and shred it into a bucket and let it dry. Then add it slowly, a little at a time, to the water, then let it sit for 20-30 minutes or so. then use the power tool of your choice to give it a good mix. I used a paint mixer attachment on a drill.

Next time - Deflocculants, settling, and siphoning.

Two more saggar pots

Here are two more saggar pots from last weekend's firing. The tall vase has terra sig, the rounder form is unburnished, natural finish.


I'm hoping to get the last of them cleaned up and finished this weekend.
I've already been examining them, gathering ideas for the next time.

Light red/pink swirl vase

Here's one of the experiments that turned out.


When it was bone dry greenware, I first put a layer of white terra sig on it, then a couple layers of red. I originally intended for it to be much more red, and more of a solid coat, but the clay had other plans. Turns out the red sig streaked as the pot spun on the wheel, I'm guessing because it was still too thin/watery. I think it's far nicer than what I was going for.

One of my favorites

I really like the way this one came out. The dark grass-like line left by a copper wire couldn't be better if I'd planned it that way.

Another one waxed and polished

I got another pot finished --

Results

Overall, the results were very good. There were five of us total, and everyone was happy with their pots. It was cool seeing everyone else's forms. Some small, some large, some handbuilt from textured slabs wrapped into vases.

Unlike glazeware, after the firing the work has only started. We had to unwrap and the scour the pots to remove the ash and residue from firing. Today I began the process of waxing the burnished / terra sig'ed ones. Kinda like waxing my Dad's van as a kid, only smaller.

Here is today's effort, after mowing the yard in between raindrops and other weekend chores.

Photo montage

So this weekend I finally got around to taking pictures of my past and present work so you can see what the heck I'm talking about. I'm also going to backpost some of these into my previous posts for future newcomers.

Naked raku


These are from my one and only attempt at this. It was in a class at the art center and there wasn't much leeway for experimentation. I like the overall effect, and I can see the potential there, but I'd like to try some different masking slips to see if I can get a larger crackle pattern.

Saggar firing


These are more recent, using the tin-foil saggar method described in Alternative Kilns and Firing Techniques. Great book, full of ideas. It covers raku, sagger, pit and barrel firing, with dozens of variations.

Works awaiting the flames....

These are a few of the pieces I have waiting to be saggar fired next Saturday. The orange is the first attempted application of red terra sig. The shinier ones have had white t.s. applied and been polished. This is the last look at them before they're wrapped in aluminum foil in a cocoon of plant materials and metal salts.

First attempts with terra sig

Short for 'terra sigillata' the Romans used it to cover their pots. It's a clay slip made of only the finest clay particles. Brushed on in several thin coats, it almost shines itself. It's very cool stuff!

For my first attempt, I just used some old dried out white stoneware clay scrap I had. Searching around on the internet and the clayart archives, I'd found several recipes, the most definitive being Vince Pitelka's procedure. Not having all the equipment and chemicals needed, and just wanting to do a rough first draft, I found this article on Ceramic Arts Daily by Joan Carcia.
(Ceramic Arts Daily is a nice site, and free to join)

Being a rough test, I found I had about 2lbs of dried clay, so I used about a gallon of water, and a tablespoon ful of TSP that I found at the local building/home store.

After settling and siphoning, I poured it into a biqued bowl I hadn't gotten around to glazing yet to evaporate/absorb some of the water off. (Tip: soak the bisqe in some water first to get the pores of the clay 'siphoning' quicker)

I'm finding the white sig is working very well. Outstanding actually, for the sloppy way I followed the directions. I now have a larger batch made with red clay scraps settling, and will need evaporating. I just tried using some I siponed of the top yesterday and it's just too thin. I rubs right off when I try and polish it.

This time around, I was looking for the quick and dirty way, since I wanted to try it on some pots headed to a saggar firing in a couple weeks and I had to get them bisqued. My next attempts will be following Vince's process, and I can't wait to have some super sig to experiment with!