Category Archives: terra sig

Terra tests and bat issues

Over the long weekend I finished preparing my terra sig that I started in the garage way back in January. It’s been settled and siphoned off 2 or 3 times so should be extra fine. I got my test pieces prep’ed and ready for firing. Keeping my fingers crossed for good results there.  Next I want to do a batch of white terra sig. Maybe this time it won’t take me 6 months to get it made!

So far so good on studio time. This will be week 3 of getting in the studio consistently. It feels good. I’ve missed it.

I tried throwing on a hydrastone bat yesterday. It didn’t go as well as I’d hoped for a couple reasons. First, I’m not used to throwing on bats. Isn’t it true we tend to continue the way we were taught? I learned to throw on the wheelhead and that’s just what I do now.  Second, I had some stiff clay. Just not helpful when learning something new to be fighting your clay.  Third, the bat seemed very ‘grabby’ – sticking to the side of my hand as I was trying to center, etc. I did try and wet the bat down with my sponge, but should I have maybe soaked it?

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.


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: , which also has instructions for making one of these little gems.
There is additional information and instructions here:
and at Wikipedia here:

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.

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.