LRB04 - Lrg. Regular Pyrometric Cones #04 (50/Box)

Large Pyrometric Cones

Pyrometric cones are essential tools for obtaining reproducible results during firings. That said, here is some information we hope you will find useful about what cones are and how they work.

First off, what exactly is a pyrometric cone, anyway? Cones are composed of carefully formulated compositions. Each cone type is assigned a number (for example, cone 06), and this number denotes a specific and fairly narrow temperature range (for example, cone 06 indicates a temperature range of approximately 1800 - 1850F).

For more information on cones and their temperature equivalents you can reference the Orton Cone Chart °F.

During firings, cones are placed within the kiln, usually in a cone holder or a block of clay, and as the temperature increases, cones absorb heat. As the cone reaches the temperature that it is formulated to melt at, the tip of the cone begins to bend. It is recommended that you use 3 cones in your firing: one cone that will mature at the temperature you wish to achieve, one cone right below this temperature and one above. This will help you achieve accuracy in your temperature measurements. Because different cones require specific temperatures to mature, they will bend at different temperatures from each other, enabling you to determine how hot your kiln has gotten and whether you have reached your desired temperature. If you are firing a relatively large kiln or a kiln that you know has a temperature differential, it may be useful to place cones in different spots within the kiln, to determine whether you kiln was evenly heated.

If you are using an electric kiln, it is not required that you use cones, but we do recommend it, as it will allow you to confirm that your kiln is properly calibrated.

Orton Large Pyrometric Cones measure approximately 2.5" tall. Cones come packaged in a box of 50. Please choose desired firing temperatures from the DROP-DOWN menu above.

Temperature Equivalent Chart for Orton Cones (Cone #022-14)

Pyrometric Cones have been used to monitor ceramic firings for more than 100 years. They are useful in determining when a firing is complete, if the kiln provided enough heat, if there was a temperature difference in the kiln or if a problem occured during the firing.

Cones are made from carefully controlled compositions. They bend in a repeatable manner (over a relatively small temperature range - usually less than 40°F.) The final bending position is an indication of how much heat was absorbed. 

How Cones Behave

Typically it takes 15 to 25 minutes for a cone to bend once it starts, depending on the cone number. The cone bends slowly at first but once it reaches the half way point (3 o’clock), it bends quickly. When the cone tip reaches a point level with the base, it is considered properly fired. This is the point for which temperature equivalents are determined. Differences between a cone touching the shelf and a cone at the 4 o’clock position are small, usually 1 or 2 degrees.

Temperatures shown on these charts were determined under controlled firing conditions in electric kilns and an air atmosphere. Temperatures are shown for specific heating rates. These heating rates are for the last 100°C or 180°F of the firing. Different heating rates will change the equivalent temperature. The temperature will be higher for faster heating rates and lower for slower heating rates.

Cone bending may also be affected by reducing atmospheres or those containing sulfur oxides. Orton recommends the use of Iron-Free cones for all reduction firings (cones 010-3). If a cone is heated too fast, the cone surface fuses and binders used to make cones form gases that bloat the cone. If cones are to be fired rapidly, they should be calcined (pre-fired) before use. Cones should be calcined to about 850°F (455°C) in an air atmosphere. If a cone is soaked at a temperature near its equivalent temperature, it will continue to mature, form glass and bend. The time for the cone to bend depends on several factors and as a general rule, a 1 to 2 hour soak is sufficient to deform the next higher cone number. A soak of 4 to 6 hours will be required to deform two higher (hotter) cones.

Our own experience with Cones: 

It's important to use the correct size cone for the job. There are 4 types of cones, Large Cones, (site cones), Large Self Supporting Cones, Small Cones (for kiln sitters), and small bars for your sitter. The large cone is designed to be placed in either a Cone Holder or in your own cone pack. We have found we get the best results when we pre-bisque fire our own cone pack. This is only helpful when you are creating a cone pack to be fired to mid range temperatures such as cone 6.  Your target cone should always be placed in the middle of the pack, one cone below and one cone above should be placed on eitherside of the target cone. 

When is a Cone 6 a Cone 6? Have you ever wondered what a perfectly fired mature cone 6 looks like?

Simplifying the Orton Temperature Chart The Orton Cone Chart is made up of several different columns of information. Which one do I use for my kiln?

Using a Cone Template Cone Templates allow you to attach a number (bending angle) to your fired cone so it is easy to compare one firing to the next without saving all your old cones.

Why Use Self Supporting Cones? Have you ever wondered why you might want to use Self-Supporting Cones instead of Large cones? Mounting and Bending Angle is built in to self-supporting cones. All you need to do is set them on a flat surface.

How to properly mount Pyrometric Cones in a Plaque Mounting cones properly is important to yield results that match Orton's temperature charts. The video shows a few easy pointers to make sure you are mounting your cones properly.

3 Hole and 4 Hole Cone Plaques Plaques are available in 2 sizes. This video also shows how to make a 4 hole plaque into a 2-2 hole plaque if needed.

How Do I Separate my Large Pyrometric Cones? Large cones are shipped in "Compacts" (2 Connected Cones). This video shows how Orton recommends separating large cones before mounting in plaques.

How Do I Separate Small Cones? This video shows what a pair of small cones looks like and how to separate them.

Tell Me About Orton Iron Free Cones Cones containing Iron oxide make them "Brick Red" in color. Most of Orton's Cone Series are made without Iron Oxide. For customers who cannot tolerate iron oxide in their firings, Orton produces an alternate series to the red cones (between cone 010 and cone 3) called the "Iron-Free" series.

What Cones are Used in High Temperature Industrial Applications? Orton manufactures cones starting at cone 022 and ranging up to cone 42. For high temperature applications, Orton makes self-supporting cones up to cone 28, Large and PCE cones up to cone 42. PCE cones have been pre-fired to burn out any organics that are used during the cone forming process to prevent outgassing.

What Cones Are Used by Ceramic Artisits? Ceramic Artists, Potters and Contemporary Studios typically use cones between 022 and 10. This video gives a general explanation of the different ranges of cones and their applications.

What are the differences in the 4 different Cone Shapes? Orton manufactures pyrometric cones in 4 different shapes. This video is helpful to see the different cones that are available. Large and Self-supporting cones are "Witness Cones". They are placed in the ware setting to witness what your ceramic ware is being exposed to. Small cones and Bars are typically used in a Kilnsitter shut-off device. Some laboratories also use small or PCE (Pyrometric Cone Equivalent) cones as witness cones where space is limited.

Pyrometric Cones Bending Have you ever wanted to see cones bend? This time lapse video allows you to see the guide cone bending first, with the firing cone coming down next. The guard cone does not move but available if the Firing cone shows an "over fire condition.