Kilns and Water

A common question these days is about the status of electric kilns exposed to Hurricane Katrina.  Dogwood Ceramic Supply has prepared the following information to assist kiln owners. 

Please be advised there is much misinformation published on the internet regarding electric kilns being repaired.  It appears some of the information is intentionally misleading to gain favor with prospective customers who will ultimately require new equipment or is based upon faulty data.

This page was updated March 04, 2006 and again on December 09, 2006 with additional information and to improve clarity.

Rising Salt Water

Exposure to rising salt water is considered a terminal event for an electric kiln as there is absolutely no practical means to repairing an electric kiln once exposed to rising salt water.

Upon exposure to salt water the electronics and elements in the kiln, as well as the metal skin and frame of the kiln, will rapidly corrode.  Any corrosion in the electrical components can present an electrical safety hazard.  The insulating firebrick (IFB) can be destroyed by exposure to water.  Water exposure breaks down the small insulating chambers within the IFB. While the bricks will appear to be functional, the high fire capabilities of the kiln will be compromised.  In addition the IFB will absorb any contaminates, such as salt water, and the deposited salts will vaporize during kiln firing and subsequently contaminate any electrical components, metal skin or elements that have been replaced on the kiln.  Flushing IFB with water to remove any deposited salts will further destroy the insulating capacity of the bricks by breaking down small insulating chambers within the brick.

The only component that could possibly be salvaged on a kiln is the structural steel frame used to manufacturer large gas kilns.  Large being a relative word.  The kiln would need to be stripped down to the frame which would then need to be sandblasted and repainted.  As rising salt water was often accompanied by swift currents it common for the steel frames for these kilns to be bent or damaged beyond repair.  Please note, while stripping and sandblasting can be performed, the cost of such labor intensive tasks is often greater than the cost of a new structural steel frame and the cost of the individual components when purchased separately may cost more than a new kiln.

Converting electric kilns exposed to rising salt water to gas or raku kilns is not practical.  As previously noted the salt water causes rapid corrosion of all metal skin and frame of the kiln and IFB exposed to salt water will be severely compromised.

Rising Fresh Water

Exposure to rising fresh water is not as drastic as salt water, though it may not be cost effective to repair a kiln that was exposed to rising fresh water.  Exposure to water of any kind is detrimental to the life of a kiln and repairs that are made should be viewed as a stopgap measure until a new kiln can be purchased.

Modern Digital Controlled Kilns:

If the digital controller uses the sealed membrane control pads (such as the pad found on the Sentry 2.0 and older Paragon DTC 1000 controllers) and water has not seeped into the control pad, the controller should be safe to use.  If water has seeped into the control pad the controller can not be used.

Older control pads, such as the DTC 100, 600 or 800 do not use the sealed membrane.  If water has seeped into the older style control pad, the entire controller unit must be replaced as moisture may be retained between the key pad components.

Exposure to fresh water is not a terminal event for digital controllers, however the electrical circuits on the digital controller must be thoroughly cleaned and dry prior to any usage.  If the controller was exposed to water, please use an appropriate commercial electronics cleaner to clean the circuit board and insure that the board is completely dry prior to any usage.  Be aware that some electronic components, such as capacitors and internal fuses, may absorb and hold water.  Any water remaining on the digital controller could present a safety issue as well as destroy the board.

The digital controller powers several relays located at the bottom of the control panel.  If the relays were exposed to water, the relays MUST be replaced.  The dust seal on the relays are not sufficient to prevent water from entering the relays, but the dust seals will retain moisture and present a safety hazard to the user.

Sealed thermocouples are not water proof.  The seal on the thermocouple is for hot gases within the kiln. Sealed thermocouples must be replaced if exposed to water as the insulation within the thermocouple will retain moisture.

Replace any electrical wire, power cord set and connections that were exposed to water.  The wire insulation will retain any water that has seeped into the wiring and will cause serious electrical safety issues for the operator.

Elements and connectors that are exposed to water will corrode and must be replaced.

Insulating Firebrick can be destroyed by exposure to water.  The water exposure breaks down the small insulating chambers within the brick. While the bricks will appear to be functional, the high fire capabilities of the kiln will be compromised.  Insulating Firebrick exposed to rising fresh water should be replaced.

Please note: elements are generally 15% of the cost of a new kiln, the control panel components (digital controller, relays, thermocouple, internal wiring and cord set) are generally 1/3 to 2/3 the cost of a new kiln.  Brick costs are relatively minor, though time consuming to replace.  Labor costs are not included in these estimated costs.  In many situations it would be more cost effective to purchase a new kiln than trying to salvage a kiln exposed to rising fresh water.

Electric kilns exposed to rising fresh water may be converted to gas or raku kilns with very limited success.  As previously noted exposure to any water is detrimental to the life of the kiln.  The metal skin and frame of the kiln will rust (though not as quickly as a kiln exposed to salt water) due to water exposure.  The insulating capacity of the IFB exposed to rising fresh water may be compromised if the small insulating chambers within the brick have been damaged.

Old Style Mechanically Controlled Kilns:

For older kilns that are not equipped with the modern digital controller, exposure to rising fresh water is much the same as the digital controlled kiln.  It may not be cost effective to repair a kiln that was exposed to rising fresh water. 

Electrical wires, connectors and power cord sets must be replaced if exposed to rising water.  Any element switches or interval timers that were exposed to rising water must be replaced.  Elements exposed to water must also be replaced.

The Kiln Sitter shut-off device is a mechanically complex device.  It is strongly recommended to replace the entire unit if it was exposed to water.  Please note while it is possible to dismantle and clean the Kiln Sitter unit using commercial electronics cleaners, the difficulty in performing such a task as well as the amount of moving metal components which will subsequently corrode makes cleaning the unit a temporary repair at best. 

Water Spray

For kilns exposed to water spray the degree of water exposure is the issue.  Water that enters the control panel at the front of kiln may cause serious safety and corrosion problems with the kiln if not properly dried prior to use.  Evaluate the water sprayed control panel the same as you would the rising water sections above.  Water spray on the exterior of the kiln may aggravate corrosion issues with the metal frame and case.