Hawthorn Clay For Cob Ovens:
HAWTHORN BOND 35M Fire Clay- 50lb Bag Dry Clay
People use many different types of clay for backyard ovens for bread and pizza and more. We recommend Hawthorn Fire Clay Mix because of it's workability and affordability.
This dry clay is much less expensive than a "potter's clay" which is
usually a moist clay with fluxes and glass formers which are not needed
for a clay oven.
This fire clay mix will be delivered to you via speedy US Postal or UPS. Depending on your location, 50 pound bags of plasters may ship UPS
or may ship US Postal in two 25 pound units in a strong plastic bag which you can reseal with twist-ties that are included.
The price shown is for the northeast United States (ME, NH, MA,RI, CT, VT, NY and NJ)
Please select "zone B" option which adds just $5 postage if you are not in one of those states.
Coarse fire clay mix (either 20 or 35 mesh) is "toothy" so it is a good clay for any kind of adobe construction.
For this type of oven building, people will mix the clay in various proportions with chopped straw and sand.
Masonry sand is always recommended over "play sand" : Play sand is usually a river-run sand so the particles are smooth and round making it suitable for a sand box, where a mason's sand is a more block-like shaped particle which microscopically stacks like tiny bricks making it suitable as an aggregate in cement, mortar and clay or adobe blends.
Clay adobe ovens do not get hot enough to actually turn the clay to hardened ceramic like it would in a kiln firing. The cob oven clay will be quite hard to the touch but will turn soft again in rain so backyard ovens should have a shed roof or some other way to protect it from the elements. Some folks add some Portland cement, especially in a finish coat to help give a bit more water resistance.
We offer this fire clay mix for it's use in pottery making. Since oven building is beyond the scope of the manufacturers' recommendations to use this for oven building projects, we cannot really guarantee it's performance. All we can say is that , people have told us that it works well !!! So TEST TEST TEST !!! It is up to you to make sure this Hawthorn clay is going to work with your methods.
The items people order from us for their oven building projects are fire brick and kiln shelves. Our high temperatures bricks are used as the floor and or walls of the oven. Kiln shelves are commonly used as a nice smooth floor or like a pizza stone. Again, these applications are beyond the normal usage for these materials. Kiln shelves are not FDA rated for food. We make no claim as to their suitability, all we know is that pizza and bread makers order this Hawthorn clay all the time!
IN STORE PICKUP
You must call 24 hours in advance of your visit to pickup clay and other raw materials
Quantity discounts and Bulk available. Please call to order large quantities. 888.774-2529
A plastic fireclay exhibiting outstanding plasticity and workability.
Firing Temperature 1800F 2000F 2200F 2400F
Approximate Cone (Small) 08 04 4 9
Dry Shrinkage (%) 1.7 4.4 8.5 N/A
Fired Shrinkage (%) 4.2 7.9 11.4 11.7
Fired Color Tan-Pink Tan Yellow Gray-Yellow
LOI (%) 12.99 12.92 13.67 N/A
SiO2 47.1 - 53.3%
Al2O3 30.3 - 32.1%
Fe2O3 1.3 - 1.7%
TiO2 1.7 - 2.2%
K2O 0.6 - 1.0%
MgO 0.2 - 0.4%
CaO 0.3 - 0.5%
Na2O 0.1 - 0.3%
P2O5 0.1 - 0.3%
LOI 10.5 – 15.55%