Oven Curing

[CanuckJim]

Re: Oven Curing

Hendo,

I agree entirely with the notes on keeping fresh concrete damp. This is particulaly true with refractories. When I poured the refractory slab (LaFarge Fondue and aggregate) for my oven, I bought a roll of burlap, covered the slab with it and kept it damp for about a week. This method adds strength and also retards shrinkage. Followed the same procedure with the cladding.

Jim

[Hendo]

Re: Oven Curing

In terms of heat curing the refractories, as opposed to moist curing the mortar, I?ve found the following spec sheet for heat-up procedures for refractory products, albeit in degrees Centigrade, rather than Fahrenheit (I?ll leave it to you to do the conversions).

Quite interesting (and hopefully useful), but note the caveat in the top left text box!

[CanuckJim]

Re: Oven Curing

Hendo,

Interesting stuff. I ran into something similar for kiln curing. It would probably be difficult for us to use the procedure under such controlled conditions, though. You'd have to be out there constantly for hours on end. Still, it's probably the best way for ultimate strength.

Jim

[jengineer]

Re: Oven Curing

The chart starts out at ambinet conditions. You then ramp up at ~120 F/hour until you hit 400 F. (it might be easier to ramp up at 100/hour to 400 F = 4 hours). From 400 F you then ramp up at no more than 400 F / hour until you hit the max operating temp say 2190 F. Getting you oven equlized at 2190 is a snit on the hot side.

[RTflorida]

Re: Oven Curing

I hope to complete my dome this weekend, my question - does it make sense to go through the curring process BEFORE insulating?? I thought that I read somewhere early in my research that curring the dome prior to insulating allows you to "patch" any cracks that occur in the dome and refractory mortar layer...then insulate/finish and cure again.

Does this make sense, or should I just go through the curring process once, after insulation?? I'm doing an igloo with 2" blanket, 4" perlite/cement, then either stucco or mosaaic tile.

RT

[dbegler]

Re: Oven Curing

Hello,
I have a new oven (yay!) that I'm starting to cure. I've had 3 fires so far - 1st - newspaper, 2nd - kindling, 3rd - kindling plus 1 piece of wood. Each of these fires have got going and then died (and smoldered) really quickly (15 minutes).
Am I doing something wrong? Is this due to the moisture in the masonry? Or am I not getting an initial blaze hot enough?
Any suggestions would be appreciated.

Thanks,

David

[james]

Re: Oven Curing

Welcome aboard David,

Your oven might still be damp enough to keep everything from catching and burning all the way down. That's the general idea. Try to get a real fire going with the amount of paper and wood you have -- it ths small amount of material that limits the BTUs you put in the oven.

Also, this part isn't rocket science, or a swiss watch. The general rule is limit the first fires to a small amount of material; grow the fire size slowly in order to not shock the oven and to slowly cure out remaining moisture; and take your time in building up your temperature to where the dome goes white. Take the full seven days to do it right, and don't jump from 2-3 really small fires, to a whopper where the whole dome goes white.

Let us know how it cooks -- and make sure you download the Wood-Fired Cooking e-Book. http://www.fornobravo.com/store/.

James

[RTflorida]

Re: Oven Curing

David, listen to James, take it slow.
I'm down to my last curing fire (800 degrees tomorrow). It has been VERY, Very tempting to "go for it" the past 2 days.
HAve not experienced any issues with my dome - no cracks, no steam, nothing - had a sustained (about 25 minutes) dome temp of 750 degrees today. The ONLY issue I need to address is a hairline mortar crack in my entry arch. I believe patience has been the key, and taking the time to follow the instructions. Those who have built before us have worked out all the bugs, so to speak.

Good luck, keep us posted

RT

[RTflorida]

Re: Oven Curing

James,
as I just mentioned, i will be going for 800+ degrees tomorrow. Should I keep it near that temp or can I build that 'scary fire' I've read about? (thats my inner pyromaniac speaking).
Thanks

RT

[dbegler]

Re: Oven Curing

Thanks for the advice. It got a little hotter tonight, but the wood (almond) doesn't seem to be catching and burning all that well, and smoking more than I think it should. So I suspect I'm either a) not putting enough kindling in to ignite the wood, or b) just have wood that's wet, or not properly seasoned.

Problem is, I have nothing to compare it to, so I'm not quite sure.

Anyone know a good wood supplier that delivers in San Francisco?

thanks,

David

[maver]

Re: Oven Curing

I don't know a wood supplier, but you can test whether it's the wetness of your wood by leaving some in the oven after your next firing to let it "kiln dry". Rake the coals out first. Usually I need to let my oven drop in temperature for a while before I place wood back in the oven (If I don't wait long enough it will smolder for hours), but once you are reaching 800 degrees the oven should hold enough heat over the next 24 hours to significantly dry your wood. Helps to place a door at the entrance or make a temporary occlusion by stacking bricks at the entrance. Even with my wood that's been aged a year and covered I need to do this if I want my fire to start easily (but I live in the damp pacific NW).

[james]

Re: Oven Curing

RT,

Seven days and 800ºF. You are definitely ready to cook! My only thought is that your oven is going to get better every time you use it for at least a week or so, and you don't have to push it. Also, if you have a pizza party, or reason to cook longer, you can always keep it fired longer, without necessaryily getting hotter -- which will help.

You will definitely "feel" the oven getting more responsive and getting a little hotter a little faster each time. Hah, I am having this vision of your oven talking to you. Yikes.

David,
I grew up in the central valley, and have a lot of experience with Almond. It's great wood. If you can't even get the kindling sized pieces to really catch and burn, it might be damp. Go for the oven kiln drying idea that Maver had.

Let us know if you find a good wood source. Are you right in the city?
James

[dbegler]

Re: Oven Curing

Hi James,
Yes, I'm in the city. I'll try the wood drying technique you and maver recommend, and let you know how it goes. Thanks. -- David

[CanuckJim]

Re: Oven Curing

David,

Kiln drying, or coking as its sometimes called, definitely works, and you should try it. Also, compare two pieces of your firewood: one that you know is not cured, and one that you think is. The cured piece should be darker on the cut ends and show a pattern of radial cracks or checks. A cured piece of the same type of wood should be noticably lighter in weight than an uncured piece of similar size. Eventually, you'll get a feel for this. My procedure is to stack my uncured wood on the left side of my woodshed and the dry stuff on the right. Avoids confusion and temptation.

Jim

[james]

Re: Oven Curing

Wet wood is terrible. Our daughters know what I mean when I am muttering about asbestos wood -- it just won't catch.

Has anyone used a moisture gauge? The last time I used one was a few years ago when I need to test whether my hardwood floors were dry enough to sand and varnish.
James