Firing Greenware (NOT Porcelain or Stoneware): Date Added: 5 May 2017 About:

The Basics

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It is not a good idea to load your items on the bottom of your kiln, you should use some short stilts and place one shelf over the bottom and then build up your shelves to heights needed.

Try to load your kiln evenly, arranging items of the same height on each shelf.

Shelves should be placed so that at least one kiln element is in between them in order to make sure heat is evenly distributed.

Knowing ahead of time what your greenware will be used for, is important so you will know what cone you will fire the kiln. Utility pieces such as cups, dishes, bakeware, etc. should be fired at a hotter temperature to give them maximum durability. If a cup is fired too low and then eventually put in a microwave, it can break, same with pieces you may use to bake with. It is most commonly recommended that utility pieces as mentioned be fired to cone 02. This will make them less porous and stronger. Items that will be glazed will need to be fired at least one cone, preferably two cones hotter than the glaze firing unless the glaze instructions direct other wise. This is necessary so that the ware will shrink enough during its initial greenware firing that it won’t cause stress during the glaze firing. Items that will be stained can be fired at cooler temperatures as low as 05-07 and they will produce a softer, more porous surface.

As a rule of thumb, I recommend that greenware for all utility pieces be fired at cone 02 and all other pieces be greenware fired to cone 04. This allows the operator to load the kiln full and not have to break out every item into many smaller loads. However, the artist/ceramist may have specific reasons and desire to fire at a specific temperature and their wishes should be accommodated if at all possible. At cone 04 the ceramist can choose to use glazes or stains and know that their item will be compatible to either.

In most cases, greenware that has underglazes applied, can be fired with any other greenware as long as they do not touch each other. Greenware that has no underglazes can be touching each other and even layered lightly. If you use any underglazes, be sure to read the instructions before firing. Do not over crowd your ware, pack it loosely so that the heat and air can circulate and gases vent out.

Items with lids should be fired with lids in place. The mouth of the container should be big enough that the lid has some movement when in place or they may not come off after the firing. Greenware shrinks when fired, anywhere from 8 – 25 percent depending upon what kind of slip is being used. If you fire items with lids separately, they may not fit afterwards because of shrinkage or warpage from the firing process.

Where possible, items should be fired in the same position they will be used. Example figures, boxes, jars, etc. should be set in the kiln upright and not lying on their sides. There are exceptions to this such as large flat items, platters, trivets, etc. – these may require special attention. Items such as ornaments, round items, etc. can just lie on the shelves loosely.

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