Finishing your Pottery: Glaze Fire

Do you live near Princeton, New Jersey? Come visit me at the Crafter's Marketplace on November 19 & 20, 2011. Find great handcrafted gifts for someone special.

Firing Your Pottery: Step 2

Once glaze has been applied to a pot and allowed to dry it needs to be fired again to get the glassy surface most people think of when talking about pottery, so back to the kiln! The pottery is placed on shelves again, just like with the bisque firing, but with glaze firing you can’t stack pots one on top of another because they’d fuse into one when the glaze melts so no touching! Not pot to pot, pot to shelf, or anything else.

When I fire my medium-sized kiln to it takes about 8 hours to reach maximum temperature (2192°F; ~1200°C) and I let it cool down overnight. The pots are still warm to the touch when I open the kiln the next morning.  But don’t sneak a peek! Opening the kiln while it’s firing or cooling can let in a draft of cold air which can lead to cracking, which would be a shame given all the hours you’ve already put into making that pot.

Glazed pottery before firing.

And the same pieces of pottery after firing. For the giraffe plate, I hand painted the giraffe with black underglaze prior to adding the translucent brown glaze on top.

As you can see the color of the applied glazes frequently don't resemble the final fired glazes. This is why potters like to use test tiles, to give us a better idea of what the glaze looks like once fired.

So now you know, pottery making is a laborious process that involves several steps and many, many hours (even if it’s just waiting for a pot to dry or be fired). People often ask artists why a piece of pottery costs so much, it’s not so much the cost of the clay or glazes, or the electricity/gas to fire the kiln, or even the capital investment of the kiln, it’s really the experience that potter has gained over the years of practice and the time it takes to create each piece of pottery by hand. 

And you ask what about the ceramic dinnerware set I can buy for $25 at the local big-box store? The difference comes down to volume, when ceramic pieces can be made by the hundreds using a mold, glazed in en masse, and fired in gigantic kilns, we’re talking a whole different ballgame. Artisans you see at craft fairs, on Etsy, and in galleries have hand crafted individual pieces of art for your enjoyment.

I hope you’ve enjoyed this overview of pottery making. If you want to learn more there are hundreds or books and probably even more websites dedicated to the art of pottery making. And if this has whetted your interest and you want to give pottery a try, check your local art centers, schools or community colleges, they typically offer pottery classes for all ages and skill levels.

Next time I will tell you about raku, a unique firing process that produces beautiful metallic glazes.

Getting Ready for a Craft Fair

Spent all weekend getting ready for a craft fair that I will be selling at next weekend. I thought the fairs were exhausting, but it seems like the preparation is just as exhausting if not more so! Selecting which pieces to bring, pricing, layout (not too little, not too much stuff).

Have a slightly new set up, so I did a test run in my living/dining room this weekend!

Had a friend over to help me with pricing and she took some great shots of some of my stuff. Thanks Sassi!

If you are in the Princeton, NJ area you can come see me on Nov 19-20 at the Crafter's Marketplace.

Making Ceramic Pottery: Glazing

Do you live near Princeton, New Jersey? Come visit me at the Crafter's Marketplace on November 19 & 20, 2011. Find great handcrafted gifts for someone special.

Glazing

A glaze is a special kind of glass which is chemically formulated to adhere onto the surface of the clay when fired. Most functional pieces of pottery are glazed to make them water resistant, durable, and easy to clean. Glazes can be found in all kinds of colors and opaque or translucent.  Many potters mix their own glazes using time-tested recipes or experiment with chemical combinations to make new colors or textures. Since this isn’t a full time adventure for me, I buy ready to use, commercially available glazes.

My stash of glazes.

 

Glaze can be applied in many ways including dipping (dunking your pot into a vat of glaze), brushing (just like painting), pouring (the glaze over the pot), or spraying (using an airbrush-like device).  Layering glazes one on top of another can produce an infinite number of color combinations and effects.

This is my glaze board. The tiles are called test tiles because they allow me to see what the glazes look like on the clay I use. Each tile set is a pair, one in brown clay and the other in white clay - a glaze can look very different depending on what clay it’s applied to. I also apply one glaze on the top half of each tile and another glaze on the bottom half with an overlap of about an inch in the middle. This lets me see what glazes look like when layered.

 Next time: Finishing your pottery, the final firing.

Firing Your Pottery: Step 1, Bisque Fire

To get to the point where you have a shiny, maybe colored, piece of pottery in your hands takes two firings in the kiln. Bisque firing is the first firing. 

Once you’ve make your ceramic piece by whichever technique you prefer (hand built, thrown, etc.) and its dried sufficiently, it can be bisque fired, which leads to a hardening of the clay. How dry is dry enough? Good question. That depends on the environment since weather can effect drying times hugely. If it’s humid, pots will take longer to dry. But be careful, if that pot is not completely dry it can explode in the kiln. I've been there and done that and it's quite a mess to clean up and not good for the kiln’s heating elements.

This is my medium-sized kiln

This is what the pottery looks like when stacked in the kiln. 

This will be the bisque firing (pottery can be stacked during the first firing). This side view stack of pottery is actually sitting on top of my big kiln (I’m 5’5” and the big kiln comes up to my waist!).

Here's a top view as I'm loading the kiln.

Once the firing is done you have to wait several hours for the pieces to cool down so you don't burn your hands touching them.

Next post it’s time to glaze!

Making Ceramic Pottery: Trimming

Trimming

Trimming excess clay off the bottom of a pot not only makes the pot lighter in weight but also refines the shape and adds interest to the pot. A footring (or foot) is a raised circle of clay at the base of a thrown pot on which the pot will stand and is a typical end product of trimming. Sometimes trimming a foot can actually take longer than throwing the pot!

To trim a foot you must wait until the pot has air dried a bit to the leatherhard stage (clay is no longer malleable, but will crack or distort if pressure is applied). Trying to trim a foot onto a pot that has just been throw will end in utter disaster since the pot will collapse under its own wet weight. 

Trimming: this is a plate that's been turned upside down so that I can trim and add a foot to the bottom.

The device with the black tabs is an ingenious device called a Giffin Grip, best purchase ever! It snaps onto the wheel head and the tabs slide in to center and hug the piece so it can be trimmed.  The old school way uses wads of clay to hold the pot in place, and they never stay!!

Trimmed plate with a foot. In addition to adding the foot, I've also rounded out the bottom of the plate to remove extra clay and make it more pleasing to the eye.

These are the tools used to trim - as you lean the sharpened metal edge of the trimming tool against the clay (while the wheel is spinning) ribbons of unwanted clay are removed from the pot. The flat metal tool is pressed against the clay to produce a smooth surface.

Next time: Glazing. How those pots become colorful.

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Making Ceramic Pottery: Throwing on the Wheel

Wheel Throwing

 

My preferred technique for making pottery is throwing on the wheel. Throwing  is the term used to describe how the rotating wheel ‘throws’ the clay outwards while the potter uses their hands to control and mold the clay against this force.  Keeping the clay in the center of the wheel (centering) may appear effortless, but it is a skill that takes great patience and lots of practice! 

Throwing a ceramic piece on the wheel starts out with centering of the clay. Repeatedly bringing the spinning clay up into a cone and pushing it back down until the lump of clay spins evenly and without any wobble (indicating it's off center). Water is used to lubricate the clay so that it spins smoothly in your hands.

 

Opening up: a process of pushing down in the middle of the centered clay and pulling out, creating a mouth

Pulling up: repeatedly pulling up on the clay while the wheel in spinning; the wall of the cylinder gets thinner as the vessel gets taller as you can see in the following pictures

And now to finish the piece - the desired shape is formed, edges and walls smoothed out.

Finishing: in this case I have narrowed the opening of the cylinder to create a small, narrow opening, like you might see on a jug or a luminary (which is what this will be). Here I'm using a wooden tool called a rib to push against the clay and smooth its surface.

Once I’m satisfied with the vessel I’ve created, I can either cut it off by sliding a fine wire between the bottom of the pot and the wheel head, remove it from the wheel and leave it to dry completely, or trim the bottom to create a footring (or foot). A foot is a raised circle of clay at the base of a throw pot on which the pot will stand.

Here are examples of freshly thrown pieces. Here you can see some ring holders, plates, and a small bowl (cylinder). The plates are sitting on ‘bats’. A bat is a piece of pressboard that can be taken on and off the wheel head allowing you to move the piece without cutting it off.

Before the pieces I've thrown can be trimmed they must firm up a bit by drying to what's called the 'leatherhard' stage. At this point the clay can still be marred if you push your fingernail into it but it's not so soft that you can distort the shape with the push of a finger. 

Next time I will show you how to trim a foot.