Blog July 2015
A great tutorial on two rules of joining clay
with a great recipe for magic slip by Lana Wilson
- 1 gallon water
- 3 tablespoons or 9.5 grams liquid sodium silicate
- 1 1/2 teaspoons or 5 grams soda ash
10 Hot Kiln Tips
by David Gamble
1. Before you fire. When installing your kiln, make sure it’s at least 18 inches away from any wall. Vacuum the interior of the kiln, especially the element grooves, about every 20 firings, and after every firing when a piece blows up in the kiln. Inspect hinges and handles for wear.
2. Check the thermocouple(s), and replace if necessary. Every six months, unplug the kiln (if your kiln has a plug) and inspect the prongs as well as the insulation. Brown or black discoloration indicates a worn plug or loose wires and a potential fire hazard. Keep all flammable, combustible and meltable materials (cardboard, wareboards, newspaper, fabric, vacuum hoses, plastic, etc.,) away from the sides and top of the kiln. These areas get extremely hot.
3. Protect your shelves. Kiln wash protects your shelves from glaze drips. Inspect shelves prior to firing and recoat any bare spots or recently cleaned and scraped shelves as needed. Remove any loose or chipped kiln wash that make flake onto pots during the firing. Store unused shelves in a safe and low-traffic area.
4. Always use cones. Pyrometric cones are formulated from ceramic materials including clay, oxides, feldspars, and frits, and are designed to bend at specific time/temperature combinations to give you an accurate reading on the heatwork created in your kiln. Cones measure the relationship of temperature absorbed by the ware over time. Tip: Use cones even if you are using an automatic kiln controller. Cones verify the accuracy of the controller.
5. Clean up greenware. Signatures and decorations leave burrs that must be removed using a damp sponge while leather hard, or drywall sanding screen for drier work, before the bisque firing. Once fired, the only way to remove these is by grinding with a Dremel tool, or sanding with wet/dry silicon carbide sandpaper. Handle greenware with care. Bone dry greenware is fragile—more fragile than when it’s leather hard. Never pick up pieces by any appendage or handle.
6. Fire dry pots. To see if a pot is dry, touch the pot to your cheek. If it is cold or damp, there is still moisture in it and you will need to preheat the kiln to 180°F and leave it at that temperature and vented until all moisture its gone. Water boils at 212°F (100°C), and that’s the temperature where there’s danger of blowing up pieces. If the moisture is not driven out and the temperature rises to water boiling levels, the rapid expansion of the steam that’s created blows out the walls of your piece.
7. Wipe your feet. Any glaze that touches the shelf during a firing sticks to it. Carefully sponge off any glaze within ¼ inch of the bottom of the foot. For pots with thick or runny glazes, clean off a bit higher than that. Do not rely on the kiln wash to save the pot or the shelf from being damaged by glaze drips.
8. Loading greenware or glazeware. Electric kilns heat from the outside walls, where the elements are located, in towards the center, so stagger the shelves and place taller pots in the middle of the stack to promote better heat penetration to the middle of the kiln. Greenware pieces can touch and can be stacked in some cases, but I prefer to leave space between them for even heat distribution. When placing a large flat piece on the top shelf, allow approximately 5 inches of clearance to the top. Extra clearance allows for heat from the sides of the kiln to travel up and over, reaching the middle of the piece so that all areas heat evenly. If wide pieces are heated unevenly, the expansion rate of the side may be considerably different from that of the center of the piece, which will cause it to crack. In all firings, keep a the edge of the stack at least 1 inch from sides of the kiln.
9. Bisque fire slowly. Clay contains organic material that needs time to burn out. If you raise the temperature of the kiln too fast, gases will become trapped in the clay body. Organic materials burn off between 572°F (300°C) and 1472°F (800°C). Also, if not completely burnt out in the bisque, organics may give you trouble in the glaze firing as it as escapes a
10. Keep records. Keep a firing record of firing times (lengths), the cones you used and the result of their melt (draw a quick sketch of
how they looked, or note whether the target cone was at 1, 3 or 5 o’clock for example), and record the number of firings in a particular kiln. These records can give you indications on element wear (e.g., if firings take longer than usual) and future
maintenance that may be needed.
Copyright © Ceramic Arts Daily 2007-2014.
This is a youtube video on loading a glaze kiln. The website also has other videos about kiln firing:
I have been handbuilding of late. When in business I felt handbuilding too slow and now have finally given myself permission not to throw, without guilt!
But I still love throwing and have found a site that offers some great demos. Here it is: https://www.youtube.com/watch?v=sowkjE_G9cQ&feature=share I will add more to this post as I find them.
more instructional videos on throwing:
Here's a japanese video I found on youtube. Note that the wheel is going clockwise!
And here's a rich collection of demos:
I found myself making a tool today. I don't know about you but I find the necessary task of scoring the edges of two sides of clay to be joined, tedious!
I have made a tool to quickly score the edges. I line up about 12-14 straight pins on a heat resistant surface. I used a ceramic tile. Once lined up with tips in an even row, squeeze out alot of glue from a glue gun then let it cool.
Once cool pull up the hardened glue with the pins suck on it and flip it. Now copy the same action on the other side, totally enclosing the pins in glue'
I quess one could use a craft glue like E-1000, but I like the immeadacy of the hot glue gun.took me about 10 minutes to make mine today.
a site that ijjustrates more tool making:
Have fun potting!
I was surfing through pinterest today and came upon a site for egyptian paste. I decided to talk about it tonight.
I love egyptian paste, also called Faience. It is a great medium for chilren and very promising for adults! One down side is the toxic quality of the paste due to high concentration of colorants. So adult and child must work quickly and carefully wash their hands after. Another option is to wear plastic gloves, found in the pharmacy.
Well suited for beads or small figurines, the paste must be allowed to dry without disturbing. This is due to the nature of the paste, being clay and glaze mixed together. As the pieces dry, the colorants migrate to the surface resulting in the glaze when fired.
The colors are charactistly brilliant and very pleasing. I have included some photos in this site.
Below is a recipe for Egyptian Paste and more can be found easily on the web. Have fun!
Amy Waller Turquoise Egyptian Paste (Egyptian Faience)
(cone 010 to cone 04)
Flint (Silica) 325 mesh 85
Sodium bicarbonate 6
Kentucky OM #4 ball clay 5.2
Custer feldspar 1.9
Copper oxide 1.0