Why Even Loading Pays Off

There is nothing more disheartening than opening the kiln after a long firing to find one side of the load underfired, a couple of pots stuck to the shelf, or a bowl cracked because it cooled too quickly. Almost every one of these disappointments can be traced back to how the kiln was loaded.

Kilns do not heat evenly. Elements cycle on and off, heat rises, and the corners of a chamber rarely behave the same way as the centre. Your job when loading is to work with those quirks rather than against them. If you take twenty minutes to think about spacing, mass, and airflow before you close the lid, you will spend far less time afterwards sanding crusty stilt marks off feet.

Spacing: A Little Air Goes a Long Way

Think of the kiln as a series of small interconnected chambers rather than one big box. Air and radiant heat have to move around every piece, so a tight, jammed load will always fire unevenly.

• Leave a clear gap of two to three centimetres between neighbouring pots. That is roughly a thumb's width, and it makes a surprising difference to glaze finish.
• Keep ware back from the chamber walls. A gap of at least two to three centimetres from side elements, and never let a pot overhang the edge of a shelf.
• Leave the peepholes, thermocouple probe and kiln sitter clear. These are your eyes and ears during firing, so protect them.
• Pack bisque more tightly than glaze. Unglazed greenware can nest and stack, as long as pots are dry and not touching in a way that traps moisture. Glaze loads need generous air.

It helps enormously to group like with like. All the thin-walled cups together, all the chunky bowls together. Pots of similar thickness reach temperature at similar rates, so your soak at the top will actually mean something.

Tall Pots, Elements and the Heat Path

Tall pieces are the trickiest part of any load. Side elements radiate directly into the ware beside them, which is why the outer edges of a shelf can run hotter than the middle. A tall vase pressed against the elements may see its glaze mature early while the interior of the chamber is still catching up.

The practical fix is simple: place taller work towards the centre of the chamber, away from the side elements, and surround it with lower, uncomplaining pieces such as tiles, mugs and small dishes. If a tall pot must go near the wall, give it as much clearance as the kiln allows and consider firing it on its own shelf with nothing beside it.

Remember, too, that a tall piece sitting on the shelf below acts as a chimney, channelling heat upward. Use that to your advantage by putting big forms low and modest pieces above, so the heat sweeping up meets ware rather than empty space.

Shelves, Props and Weight Distribution

A wobbly shelf stack is an accident waiting to happen, and a collapsed load in the middle of a firing is a long evening's work ruined.

• Support every shelf on at least three posts, and line those posts up vertically from one level to the next so the weight travels straight down to the floor of the kiln.
• Stagger the joints between half shelves. Never let a shelf seam sit unsupported, and avoid balancing a corner on a single tiny prop.
• Load evenly around the chamber. One heavy side and one light side will heat at different rates, and the shelves may tilt.
• Put a full, well-washed shelf at the bottom to catch drips from glaze accidents above. Lose one shelf, not a kiln floor.

If you use kiln wash, apply it thinly and evenly on both faces of each shelf, and remove any glaze drips between firings. A lumpy shelf means a wobbly pot, and a wobbly pot means a wobble that finds its way into the glaze.

Stilts and Wadding: Small Supports, Big Difference

Stilts are not a sign of laziness; they are a tool for stable firing, and knowing when to reach for them saves a great deal of grief.

Use three-point stilts under flat-bottomed pieces where the glaze has been cleaned from the foot, particularly if the base is uneven or the pot is prone to warping. Choose stilts rated comfortably above your top firing temperature, and always check that all three points are bearing weight before the piece goes in. Never use stilts under a runny glaze that has been left on the foot — you will simply weld the pot to the stilt.

For sculpture, large forms and irregular bases, bed the piece down on wadding made from a blend of alumina hydrate, kaolin and grog. Wadding grips the surface, compensates for awkward shapes, and lifts the work clear of the shelf while allowing it to move as it shrinks. Apply it in small, even pads rather than one great lump, and keep it away from any glazed surface it might bond to.

Keeping a Loading Record

Every kiln has its own personality, and the only way to learn yours is to write things down. Sketch the shelf plan on a scrap of paper, note where the tall pieces sat, and jot down the cone or controller reading at the top. After a few firings you will see patterns — a hot front left corner, a cool top shelf — and you can start loading around them deliberately.

Do this consistently and you will gradually stop worrying about balance and start trusting it. The load will go in quickly, the firing will come out even, and you can get back to the part that actually matters: making the pots.