Oven Curing

[SCChris]

Re: Oven Curing

I don't see any harm in running the heater rather than the light. Start on low heat and see where it takes things. I wouldn't want to melt the heater's plastic housing but if you can keep the heat in the mid hundreds you should be fine.

Chris

[gtofani]

Re: Oven Curing

The only problem with the heater is it has a thermostate that shuts it off when it reaches a certain temperature, it comes back on when it cools a little but the temperatures are not as high as what the light provides.

[SCChris]

Re: Oven Curing

Ah, I understand now..

Thanks

Chris

[fornoa]

Re: Oven Curing

I am almost finished building my vaulted brick dome and vent and was thinking of leaving it for a week then fire curing the oven prior to adding the insulation and final renders.

Thought this would be more efficient as any residual moisure in the mortars would not be trapped under the insulating and render layers and possibly reduce the potential for cracking of the render layers also.

Does anyone have an opinion on this? Do you think it makes sense or is there something I am overlooking.

[gtofani]

Re: Oven Curing

I have had my dome and chimney done since the second week in November, so a little over a month now. I am not in a hurry to cure it with fire, so far I have had it up to 190 degrees using only a 500 watt shop light. I have repeated this several times now.The last time, I left it in for about a week straight before it burned out on me.
I plan on using a torch to do the first few curing stages over Christmas break when I can be home.
I think a week is too soon for a fire, maybe I am being overly cautious but I like the shop light to dry out the oven prior to the fire curing.
The first day I could actually feel the moist heat coming out through the holes I had in a styrofoam door. I put two holes down low and two up high to get circulation. Each day the floor to ceiling temperature got closer together.
By the end of the week there was less moist heat coming out.
I am confident that the curing will go better now that a good bit of the moisture is driven out.

[david s]

Re: Oven Curing

The problem with lighting fires is that the top of the dome gets way hotter than the base and the outside of the floor. This leads to some parts of the oven expanding at a greater rate than others, causing stresses and cracks. The more gentle you can make the temp rise the better. Sun and wind IMO are your best way of driving out a lot of the moisture, but if you're trying to do it in winter that's not going to be of much use.

[gtofani]

Re: Oven Curing

I am wondering if drying the oven in the winter (below freezing) could be an advantage.
Even though the outside air is colder, it is also dryer than when warm out. The humidity level is closer to 0 when the temperatures are below freezing.
So a low fire in the oven will drive out the moisture in the oven without the effects of the humidity level allowing the moisture to return to the brick.

[david s]

Re: Oven Curing

You could be right. There are three things that govern how fast something will dry.
1. Temp
2. Humidity
3. Air movement

Where we live (tropics) pottery often dries faster in our winter when the humidity is low. In our summer when the humidity is high (often over 90%)

[gtofani]

Re: Oven Curing

The tropics, that will sound real nice in about a month when we are burried under the snow for three months here in Western PA.
I'll have to shovel a path to the pizza oven.

[SCChris]

Re: Oven Curing

Gino, I think the “light bulb” curing with low temp, low humidity, ambient air is almost ideal. The air that you’re heating and moving through the oven should be doing much of the drying. The Duration of this curing is allowing the whole structure to heat and, through convection, move air and dry the outer oven surface as well as inside the oven. At a week of drying up to 190F / 88C, much of the available water is gone. You’re oven is ready for more gentile heating.

If you can push the temps up to and sustain 250 over 4 plus hours, you could then step to 300 and 350 and so on. Once you get a 300F burn in your pocket and if you hold it for 4 plus hours, you might want to celebrate with a pork shoulder.


Chris

[gtofani]

Re: Oven Curing

I agree, the air in the oven was very dry feeling at the end of the week.
I will work on this over the next week or so during Christmas break.
Thanks for the tips.

[david s]

Re: Oven Curing

The tropics, that will sound real nice in about a month when we are burried under the snow for three months here in Western PA.
I'll have to shovel a path to the pizza oven.

Well, all things are relative. The heat and humidity here are really oppressive here ATM. We are escaping for two weeks, having Christmas skiing in Japan. Powder snow here we come!

[GreenBldr]

Re: Oven Curing

Where, exactly should we be measuring these recommended step-up temperatures? Several have asked in this thread, but I haven't seen a definitive answer.
Once your oven is cured, one is probably accustomed to seeing a more even interior temperature, but until then, it is very difficult to figure out how to follow the curing directions.

So, WHERE exactly are the step-up temperatures during the curing process measured, and how?

Don't let ANY location on the interior shell get more than 300F, 350F, 400F, etc while curing, or let the oven get hot enough that the factory-supplied oven door will register those temps for the entire interior?

[david s]

Re: Oven Curing

Don't place the door in position to red the temp or the fire will go out, better to leave it off to help it get rid of the moisture. I prefer to use a combination of wood and "heat beads"(brickettes), so there is little direct flame impingement, but for some unknown reason FB say this will void your warranty. You really want to try and get a slow and even temp rise. Try a cheap oven thermometer that you can place inside the oven.

[GreenBldr]

Re: Oven Curing

Okay, I use an infrared with a laser pointer. It is quite accurate.

But the question still stands. WHERE do you take the temperature? There is a huge difference between the floor, the sides, the top of the dome, outside the dome, etc.

I used the door thermometer only as an effort to take the "general" temperature of the inside of the oven.