Friday, November 16, 2018

From Pottery Kilns to Brick Ovens

Forty-five years ago I was making stoneware pottery and firing it in a wood-fired kiln to 2381 degrees Fahrenheit (1303 Celsius).

Today I build brick ovens that need not reach temperatures higher than 800 F.  But there is still high temperature material, FIRE and at the end, a wonderful product.

Last weekend, I joined my friend, Willi Singleton in Kempton, PA to fire his norborigama kiln at Pine Creek Pottery.  The twenty-two hour firing brought together Willi's many friends, colleagues, and students for a round-the-clock effort.
Willis starting the fire in a lower chamber

For those unfamiliar with the process of making clay into pottery, Willi's approach is complete.

Willi Singleton
His clay comes from two regions of Pennsylvania and is prepared at his pottery so that it is pliable enough to throw on a potter's wheel.

first fires are stoked in a lower chamber
His glazes are made from wood ashes, corn stalk ashes, and bamboo ash, which all grow around his place.

The wood that fires the kiln is local from sawmills.

Noborigama kilns are built on a hill.  This kiln has four chambers, with the exit ports of each passing to chamber above.  A 25 foot double chimney creates the draft to pull the flames through the chambers.

It is an elemental experience.  The forms, materials and skills are timeless.

Like brick oven building and baking, it is a link to our ancestors.

After a long night, the stoking proceeds to special ports in the pottery chamber itself

a couple of the families
have been helping to fire the kiln
since their children were young

ports are stoppered with clay after the kiln reaches temperature

Wednesday, November 7, 2018

Brick Ovens and CAD (Computer Assisted Design)

Most oven projects require planning.  This begins, if feasible, in a site visit with the potential customer.  The conversation often starts with the person's cooking goals and moves through the location, dimensions/capacity, and finally to the style of the oven.

Although my website shows a number of previous oven projects, I have found that every oven can be designed as a perfect fit with the customer, the customer's place and needs.  The result is that a look at the nearly 40 ovens I've built reveals that each one is different: variations on a theme.

A CAD drawing helps the process in a number of ways:

  1. It describes dimensions: footprint, elevation, roof or chimney route, wood box and oven mouth.
  2. It allows for an accurate quote on cost (and comparison to other options)
  3. It prepares me for the quantity of materials needed.
  4. It can be forwarded to the local building inspector and/or architect/contractor so that we are coordinated.
  5. It is the reference point for alterations, if needed, during the project.
  6. And lastly, it may allow the design client to build it him or herself.  For this, I provide a design consultation service.
So, what do these CAD's look like?
I originally had a CAD company set up one for cutting bricks.  I also got separate drawings for each brick in the oven. The master dome looks like this:

I've since found ways of cutting accurate brick chains for any size dome.

Depending on the situation, CAD's took these forms:

Saturday, November 3, 2018

Beyond Cob Wood-fired Ovens

bricks fitted over sand mound/form

sand as the form for later brick setting
A long-time friend built a small cob oven a few years ago.  As cob will, it didn't keep the heat for long, developed cracks, and although it was very inexpensive, wouldn't allow his partner to start baking any quantity of bread for sale.A long-time friend built a small cob oven a few years ago.  As cob will, it didn't keep the heat for long, developed cracks, and although it was very inexpensive, wouldn't allow his partner to start baking any quantity of bread for sale.
using off-cuts of bricks to create solid mass
Interior inspection and clean-up
Slim bodies only!
As his long-time friend, I gave him some hundreds of stray fire bricks and off-cuts from the precision bricks I'd previous cut for the custom ovens I build for my clients.

The four-cornered dome

Applying the vermiculite and Portland cement insulating layer

The result is a hybrid.  The mouth and flue assembly is from a cast-refractory company, who shall remain unnamed, that I represented early in my oven career.
A slow warm-up to drive the water out of the mortar
We mounded sand as you would if you were covering it in clay and sand, the cob method.
But instead of clay and sand going over the sand, we began mortaring fire brick chunks up and over the mound, filling in behind with refractory mortar.  As with cob ovens, the sand was removed when the dome was finished and set.

We also chose to make the floor rectangular but build a four-cornered dome so that the maximum space would be available for bread baking.  Low cost vermiculite and Portland cement had been cast under the floor bricks and more of this was applied to the exterior.

Subsequently, a box will be built around the oven and the cavity filled with loose vermiculite.  Roof over all.