A Weeping Oven?

[aeneas1]

oven: 55" modular dome, steel stand, concrete board facade, stucco finish.

is it unusual for such an oven, after 10 days of curing/firing (slow, methodical, per fiting instructions) and three days of full, operating temperature fires (750-800 floor, 900+ walls & cieling), to still show signs of moisture being released?

my friend has such an oven and, now that he's beginning full fires, there are a few small wet spots (approx. 2" dia.) surfacing through the stucco walls. he also discovered that, after leaving a plastic work bucket on the roof of his oven (unfinished concrete board) over night, quite a bit of condensation had formed below the bucket (although the rest of the roof seemed dry). such moisture was not apparent during the curing process - it could be that he just didn't notice - and he thinks that the full fires are causing it.

anyway, i told him that i would ask the experts here (he does not have internet access) - i'm not sure where the oven originally came from (he got it at an auction) but it does look like it may be a forno bravo "ristorante" because of the unique steel archway opening. any help would be appraciated.

[CanuckJim]

Re: A Weeping Oven?

Aeneas,

Couple of blank spots here. Was the stucco put on the exterior of the oven before it had fully cured? If so, your friend may have trapped moisture between the dome and the stucco. If this really is the case, I'd wait a bit then go back to the small curing fires, going through the same instructions he did at first.

Also, was the project rained on at any point? This would add moisture to the curing oven. Has it been very humid? Is he near the ocean?

All these variables will affect the rate at which all the moisture is driven off.

I'd have a care with the full firings for now; there is a risk of cracking. You want the oven to be fully cured and dry before monster fires begin.

Jim

[aeneas1]

Re: A Weeping Oven?

canuckjim:

thanks very much for your prompt and very helpful reply.

the oven was fired for a few days (per standard fire/curing instructions) and then the concrete board facade was stuccoed as he continued his firing process - his oven is installed indoors and the "stucco" finish was applied very, very thinly (a rather wet mix of joint compound, sand and mortar).

as a matter of fact, i liked the look/finish of his oven so much that i did the same with my indoor oven but had absolutely no problems with wet spots or moisture. not knowing any better, i even "stuccoed" my oven before i began the firing/curing process! i posted my "stucco" experience on another thread in which i was asking for stucco ideas.

but, back to my friend's oven - i asked him about rain (per your comments) and was told that it had rained during the initial stages of the curing process but that the chimney installation was true and that no rain entered the oven. he lives about 20 minutes from the ocean and the climate is always somewhat moist. but my oven is installed in a very similar area and i have had no problems.

what he seems to find most perplexing is that from day 4 (or so) through day 10 no moisture was evident despite the oven having been stuccoed and progressive daily curing fires maintained - fires that were as hot as 500-700 degrees by days 8, 9 and 10. not until he cranked it up to 900+, having thought it was entirely cured because of his 10 days of firing, did moisture appear.

[CanuckJim]

Re: A Weeping Oven?

Aeneas,

This is puzzling indeed. I didn't know this was an indoor installation. However, he should take it slowly and not rush. For now, I'd keep the temp down to about 500 or so for about a week, just to be sure, then go back up to bake temps and see what happens.

Just because no rain entered the chimney does not mean that no rain got under the flashing on the roof or around the storm collar. Every two years or so I have to re-caulk the storm collar on my wood stove chimney. Otherwise, rainwater will run down the outside of the stainless pipe, into the attic. It might be worth a quick check on the roof to make sure everything is well sealed. If not, use the best caulking you can buy and strip out the old with a knife before you reseal.

If there's a way to look inside the enclosure, you'll be able to see water streaks on the chimney if this is the problem.

Jim