Handbuilding with Stiff Porcelain Slabs

I'm still in the process of creating a new Insomnia Pottery website where my pottery blog will live.  In the meantime, I am doing my blogging at another website.  I just did a post over there about some handbuilt work using Georgie's Crystal Springs porcelain.  It's been good to work with as long as I don't rush the drying.

Here's an image of one of the pots I build and decorate in the blog...  please have a look if you are interested.

http://justging.wordpress.com/2013/01/29/stiff-slab-handbuilding-with-porcelain/

Handbuilt porcelain vase ready for the bisque kiln.  I'll fire this pot in my salt kiln with an interior glaze only.  I've been getting a lustrous pure white surface with this clay that I really like.  

Insomnia Pottery Blog News

Hello, Everyone,

I am in the process of a website redo.  www.insomniapottery.com is getting a facelift, which will make it easier for me to update and post.  All my old Insomnia hand building posts will be available on the new website.  In the meantime, you might want to check out this post on my other blog.

http://justging.wordpress.com/2013/01/14/drawing-on-pottery/

It shows all the steps in applying surface imagery to this casserole.....

Finishing the Goblets....

The goblet pieces needed a couple of days to dry slowly under plastic.

Here's a nice stem ready for trimming.  I have several small Dolan trim tools that make this easy.  The base of the stem is still massive and solid, and I like to detail the stem before hollowing out the base,

I've gone to some pains to keep the small cup at the top moist  since most of the problems I've had in the past have to do with two two segments not joining up properly.

Here's that same base with some trimmed details.  If your stem is not centered carefully, it's hard to get nice results.  You can see the little Dolan trim tools in the photograph.

Just as soon as I get it shaped, I moisten the interior surface of the upper cup with a wet finger, and stick a piece plastic over it.

Here's another nice stem ready to use.  I will probably do just a bit of carving on some of the elements of the stem.

Now, it's time to trim out the foot.

I attach the vase that I made with the goblet components to the wheelhead.  This is a carefully thrown sacrificial piece that will be used as a chuck to trim the bases of the stems.

I want it to be quite moist, so the stem will stick to it during the trimming process.  I adhere the chuck to the wheel securely with fat coils of clay.

 When you make your chuck, take care to make the top opening wide enough to accommodate  the top of your stem.
A chuck like this can be use to trim bottles, small ewers, and many other pieces that are fragile or difficult to trim.

When the stem is well centered in the chuck, you can begin to trim.  I use the same small tools to hollow out the foot.

You can see how crude the base of the foot is when trimming begins.

I like to trim the out portion of the foot very carefully, so the goblet will sit flat. It takes some concentration for me to hollow the foot.  I almost always feel that trimming takes much more attention than throwing, but that is probably different for each potter.

You can see that the trimming begun.  There's a lot of torque on the base as you trim, so moderate your wheel speed carefully.

Here's a finished stem ready to use.  There is nice form detail on the stem, and the the base is appropriately sectioned for drying.

Now, for the joining.

With the cup portion of the goblet attached to wheelhead, score its' base and also score  the interior of the cup at the top of your stem.
I like to add a blob of nice thick slip to fill any voids in the space that might be created.

Position the stem upside down on the base and turn the wheel slowly.  You will be able to see if the stem is correctly positioned.  If it is plumb and centered there will be no wobble at all if the wheel turns.

You will have a little time to adjust the position - the slip helps with that.

Here are my stems and cups, all put together.  I will dry them upside down for a couple of hours before turning them over; being careful not to let them get too dry for some surface decoration.

Here are some finished goblets and chalices.  The chalices were thrown in one piece.

Still Makin' Pots - Goblets Today....

Thanks to all of you who have encouraged me to post process and work on my Insomnia Pottery blog.  It's been a long since my last post, but I continue to receive emails from potters who have found it useful.

Today I am working in the studio to fill a kiln for Holiday sales, and wrap up a few small special orders.  Although I don't make goblets as part of my production work for shows and galleries, I have some in my studio and visitors see them and want to purchase them.  At this time, only a few chalices are left - just the thing for toasting your Dungeons and Dragons compatriots!  

To me, a chalice is deeper and has a shorter stem in proportion to the overall height of the piece.  Buyers prefer more traditionally formed  goblets with tall steps and capacious bowls.  I think ceramic goblets sort of take away half the joy of wine drinking - seeing the beautiful color of the wine through a crystal vessel. Therefore, let's use them for mead or hard cider or best of all, a delicious hot toddy....

I like to make goblets in two parts and join them.  Both sections are thrown off the hump.  The clay I am using today is B-Mix, which has many fine properties.  However, it will be the last day for it in my studio for a while...  I am going back to Georgies' Cannon Beach 10.  

I'm starting off with about 5 pounds of clay - enough for about 6 bowls and fairly thick stems.  If you are not making small pieces - lids, knobs, small tea-bowls - off the hump, I really encourage you to learn to do so.  

The only complex part is separating the object from the hump in a tidy and level manner.  I struggled with this for years until Portland potter Ken Pincus kindly showed me how to do it the right way.  If I can find a friend to shoot a little video of me doing this tiny but essential trick, I will post it here in the next couple weeks.  

In the meantime, we'll stick to the goblet making....

Here's what we want to make.  It's crude!  But it is closely thrown and well centered.  The fun part - refining the stem and adding ornament will come during the trimming process.  With a toothy stoneware clay it is possible to do more preliminary forming of the stem, but the slickery B-Mix - pretty wet, also - wasn't willing.

It's important to keep downward pressure on the top of the stem as you bring it up so it isn't hollow.  If you have been throwing spots on the wheel, it's counter-intuitive.

There is also that big, thick base.  I'll trim that out later so them stem is light and balanced.

 Here's a shot of the top of them stem.  A small rice-bowl shape is thrown into the top of the stem.

I usually cut the top of the stem off level with my string tool so that this tiny cup - about 1-1/2" in diameter - is perfectly symmetrical and  dead level.  The separately thrown bowl will nestle into this cup.

Like a spout, there is movement during the firing that can "unwind" the form.  If all is not level, your goblet may come out of the firing with a tipsy appearance that it just not acceptable.

Drying the stem carefully under plastic is simply essential.  The thin little top must remain fresh and moist so it will join properly to the cup.

Here's a nice prospective bowl for one of the goblets.  I usually make 6 or 8 stems and the same number of bowls and match them for scale and form when I do the joining.

I will dry them separately, and trim the bottom of each on to match the stem-top cups, then use a serrated rib to scuff them up, and mate the trimmed stem to the cup right on the wheel head.

With the wheel in motion, it's easy to see if the stem and cup have been matched correctly, and repair any "wobbling" that is the sign of an out-of-plumb join.

I'll show all this later this week with photos from the join-up.

This taller piece is one of the most essential parts of the process - a chuck for trimming the base of the stems.

I'll detail the shaft of the stem right side up, with the heavy base stuck to the wheel head with coils of clay.

Then, I'll insert the stem into this chuck upside down so the base is supported.  The chuck was carefully thrown to be well centered, and was not cut off the bat.  It may live to become a vase, but might also just be recycled.

I find it hard to trim out the inside of the stems but they will crack if the wall section is not reduced carefully.  The crack would be up inside, typically an S-crack, and won't spoil the pot.  But why not do it right?

Here's a nice set of components for some goblets of various sizes.   I will probably trim and assemble them tomorrow night.

Some Finished Knobs, and a Report on the New Salt Kiln

Yes, I finally did fire some of those knobs that I was blogging about back in January and February. I have been busy with other clay projects, daily work at my nursery business, and with learning to use my new salt kiln.

As you may recall from previous posts, my other kiln was deteriorating badly and needed a rebuild. With the help of co-workers from my nursery who have worked as masons in Mexico, I designed and cast the firebox, door, and arch of my new kiln. The body of the kiln was built of hard brick, with a soft brick shell for insulation. There is a much better metal superstructure than was built for my previous kiln, thanks to my brother Don who is a great welder.

First the good news - the new kiln is vastly more efficient and faster firing. It will reach cone 10 in about 14 hours, and I think it will do even better as I learn to fire it. But after just 4 firings, the cast refractory arch will have to be broken out and replaced with a hard brick arch. We just did not cast it as thick as it should have been, and the stainless steel reinforcing rod was consequently laid in too close to the interior surface. In the very first firing with ware in place - there had been a s-l-o-w curing fire as specified by the manufacturer - the arch cracked right down the center, and debris sifted onto the pots on the top shelf.

It's apparent from the image how the rebar has broken through the refractory material. It's going to be a nasty piece of work breaking out that arch. I have the original arch form, a big tile saw with a new blade, and those same guys who built the cast arch to help out.

You can see below how I set a shelf in the top of the kiln to collect the crud that same down from the cracked arch.... better than spoiled pots. I was hoping to get one more firing before Art In The Pearl, but it is not too be - it was just too badly cracked after the last firing.

I did get some very nice pots from firing 4, and am looking forward to using the kiln once the new arch is in place. Sigh.....

Building a New Teapot Form...

I've been thinking about handbuilding some new teapot forms for my summer shows. I like to apply patterns to my clay while it's flat and helpless... much easier than individually incising whole pots. I also think that teapot users like the funky, vaguely irregular bodies of handbuilt teapots. And of course, I really like to make them - the only real reason to do anything.

I had thrown forms related to this quite a few times and knew the scale and proportion that I wanted to achieve.

First, the clay has to be conditioned to be at the correct stage of dryness for cutting, decorating, and building. I undress the block of clay the night before, and leave it out for 4 or 5 hours, depending on whether or not I have a fire in the studio. In summer, it takes much less time. I just want to be sure that the clay is stiff enough that it won't collapse when I start assembling my forms. It's also much easier to do the stamping, rolling, and other surface decoration when the clay is a bit firm.

The next morning, I cut the block of clay into 3 or 4 slices so it can dry further, and will be easier to put through the slab roller. I use Slab Mat paper so I don't have to remove any canvas texture from my work. If you don't have a big block cutter like the one in the image, there are still lots of ways to cut nice slabs. If they are going to go through a slab roller eventually, it doesn't even really matter.

Using a drafting compass, I create conic patterns for my teapot. I am using stiff sheet PVC for my patterns - permanent and durable for studio use. On the pattern pieces, I will record the name of the piece, how many pieces there are, and assign a number to each piece. That really helps for storage and retrieval. I have more than 100 different patterns floating around my studio. I do try to keep each one in a labelled zip lock bag.

Here's a little mock-up of what the form will be. This step is an essential part of pattern making - it will allow me to assess the scale and proportion before whacking into the clay. As you can see from the picture, I have already reduced the diameter of the finished piece a bit to conform to my internal vision of the teapot.

Pattern making in the clay studio is a skill that can be learned. I got a major head start on the process through decades of sewing practice, where I made most of my own clothing patterns. Any craft that requires estimation and visualization will help with pottery making....

Here are the finished body patterns, ready to cut. The clay is about 1/2 centimeter, or 3/16" thick.

In my next post, I'll decorate these two components, and assemble the body of the teapot. There's a previous post that goes into considerable detail around building a spout with a mandrell, so I won't revisit that step.

Deteriorating Salt Kiln Requires Rebuilding....

I've fired my salt kiln 77 times in the past five years. I thought in the early years that I might get 100 firings, but the condition of the kiln is beginning to concern me and it's clear that it's time to rebuild the kiln. This has been a problem kiln since I first completed it - lots of desire for the salt process but not enough knowledge to build the kiln properly. Basically, there's just too much hard brick in the kiln. There were a lot of stalled firings in the first year, and then I kinda got it figured out and was able to get it to Cone 10 in about 14 hours. Those were the good days.... sigh. But then, I changed propane suppliers and they changed the regulator on the tank, and a frustrating period began with terrible long firings that barely reached temperature. There was a lot of BAD SCIENCE on my part - and my need for work for shows and galleries kept me from doing anything serious to remedy the situation.

I might have gotten my 100 firings if it hadn't been for the many long stalls, hours and hours over 2000 F with temperature barely creeping up. You can see how damaged these bricks in the right rear of the kiln have become.
The skews in the arch are also deteriorating badly. I have been researching how much of the brick in my kiln can be reused - and I will be carefully evaluating each brick before I reuse it.

With new hard brick up around $7-8 each, I'd like to reuse as much as possible. I think that I will have to buy all new skews - they don't look good.

The kiln has steel angle iron edge pieces, but I am definitely going to use a wider stock in the new kiln. I am also going to offset the chimney so that a threaded rod can hold the back in compression at midpoint. You can see the rear burner pot - I will probably still have two opposed burners. I now have some really nice Buzzer burners that will be great for the new kiln.

You can see gaps between the bricks from movement of the kiln during firing. This is the left rear corner of the kiln, seen from behind. As you can see, there's some decent looking hardbrick on the outside of the kiln that should be reusable.

This is the middle of the left side of the kiln. In the first year or when I was really struggling to get temperature, I added a layer of kaowool insulation to each side under an aluminum panel. This location has had a lot of vapor escape, and it has really eaten up the angle iron reinforcement, and just plain dissolved the aluminum panel.

Here's another vapor leak on the other side. The kaowool is completely gone from that spot, it will be interesting to see what's under there.

I'm going to have some help with this project; a couple of guys who work with me are going to take the kiln down. I will sort and grind the brick... ooohhh! can't wait.

I'll post some more pix as I proceed, gotta have pots for Showcase!