Oven Curing

[SCChris]

Curing is about both time and temperature. Your oven needs the time, with heat, to move the water out of the brick or casting. So long low burns that allow the oven to be heated gently and evenly are better than a quick superficial burn. The oven needs to be heated gentily so water migrates out of the interior of the bricks or casting and into the surrounding air. What you don't want is water flashing into steam, this flashing will damage bricks and castings.

Another problem with quick heating are cracks from uneven heating and / or thermal shock. If the oven is heated to quickly the heating will be uneven and this will stress the structure, and if the heat is uneven enough it will crack the structure. Some cracking during curing is likely if not inevitable but much can be avoided. When the oven is new, the water will retard the heating of wet areas as the dry areas heat unchecked and the oven ends up stressed due to this uneven heat. By curing with small burns, you give the oven a chance to even the heat out before the next burn and the next burn and so on.. By burning long and low the very slow heating allows the oven structure to warm evenly and once heated the water starts moving out and taken away by the convection of air moving around the oven.

My opinion is to get the water moving and keep it moving. The trick here is in not letting the fire run away and heating the oven more than what is outside of an acceptable curing routine. Some people use briquettes, also known as “heat beads” by our down under friends to control the heat. Early in the curing I like the idea of using a high intensity light, a quartz shop light and even an incandescent bulb generates a lot of heat and is safer to walk away from than a fire. It’s also dependable with regard to the heating it provides.

Chris

[GreenBldr]

I've now added an additional 50 lbs of FB mortar to the top and seams of my Casa 2G90 oven and have started the second curing run....

Just a note about adding the mortar; it appeared that there was a substantial amount of mold release agent on the oven shell that was preventing mortar from sticking well. On the initial assembly I scrubbed the shell with a wet rag in order to get it moist for the mortar. This time, I tried a wet hard bristle scrub brush, but the surface was still not wetting well, so I mixed up a very runny cup of mortar and used the abrasive mixture to scrub the surface and that was finally successful.

Now, I've used a shop light, a 1500W electric heater, a weed burning torch and finally, a real wood fire to get the upper dome temps up to about 500F over about 5 days.