Curing with Insulation or Without?

[david s]

Re: Curing with Insulation or Without?

In general I guess, but I would worry more with a cast dome or a stucco layer...not with a newly closed brick dome.

yes that is true.

[stonecutter]

Re: Curing with Insulation or Without?

As a general rule, if you see steam then you are going at it too hard, back off with the fire or risk refractory damage or cracked outer igloo shell.

In general I guess, but I would worry more with a cast dome or a stucco layer...not with a newly closed brick dome.

[david s]

Re: Curing with Insulation or Without?

If you covered green masonry with insulation then it's going to hold moisture..so yes, that would be normal to see steam. You do what you gotta do.

As a general rule, if you see steam then you are going at it too hard, back off with the fire or risk refractory damage or cracked outer igloo shell.

[oasiscdm]

Re: Curing with Insulation or Without?

Just keep slow consistent fires, when you think ithe I insulation is dry, it isn't. Toys over dome clear plastics you will see more moisture. I believe blanket on as it equalised the oven, potentially minimising cracks, others believe off.,

I cured mine for over a month before rendering. Of course ed cooking while this was happening no point wasting the heat

[stonecutter]

Re: Curing with Insulation or Without?

Stonecutter, posted more pictures and my weekend progress. I had what I believe is steam or moisture in my ceramic blanket after starting my cure. You could actually see it rising. Is this common? I had to insulate before I began the cure , because of the "steps" that are in my build. In other words I would not have been able to kept laying up the venneer without insulating first.

If you covered green masonry with insulation then it's going to hold moisture..so yes, that would be normal to see steam. You do what you gotta do.

[Campmaki]

Re: Curing with Insulation or Without?

Anyone else have moisture/ dampness in their ceramic blanket after starting the curing process?

[Campmaki]

Re: Curing with Insulation or Without?

Stonecutter, posted more pictures and my weekend progress. I had what I believe is steam or moisture in my ceramic blanket after starting my cure. You could actually see it rising. Is this common? I had to insulate before I began the cure , because of the "steps" that are in my build. In other words I would not have been able to kept laying up the venneer without insulating first.

[stonecutter]

Re: Curing with Insulation or Without?

Also, if there is no enclosure being build on the oven, and you are covering a blanket or batts with perl/verm crete or stucco, then the insulation should be coated with rigidizer or some other coating* to block or hinder water transfer from the insulating concrete into the insulation itself.

* I made a slurry with acrylic admix and Portland to paint on to my ceramic gaskets. Applied in July, it is still hard, though there are capillary cracks. Those didn't show until at least 6 months of use of the oven. It is a cheap and easy material to use to coat the insulation to block a lot of water out. The addition of a product like Dry Block would be even better...and it doesn't matter if this layer cracks down the road, it's only there to serve a temporary purpose, until the insulating crete dries.

[stonecutter]

Re: Curing with Insulation or Without?

For what is worth, I don't dry any of my ovens with insulation on.
That is counter intuitive to what I know of masonry...it needs to breath to dry.

With any oven, you generally want a conservative drying schedule, and if anything, you will drive out more moisture in the early stages without insulation than with it, because there is also evaporation on the outside surface from the atmosphere when there isn't a live fire in the oven.

Additionally, equalizing the heat is not going to happen early in the drying schedule, because of the amount of water in the masonry and how little heat is being introduced to it early on.

So it stands to reason that laying insulation over the dome in the early drying schedule is trapping moisture in the dome longer than if there was nothing over the oven. I do see a benefit of adding insulation just toward the end of the drying process, when you are near or at operating temps, to help even the heat distribution through the masonry.

Bottom line, it doesn't really matter. Be conservative, and the oven will dry eventually.

[NCMan]

Re: Curing with Insulation or Without?

That's the plan.

[UtahBeehiver]

Re: Curing with Insulation or Without?

NC,

Do what you think you need to do, documented or not. A lot of our building processes are based our experiences and those preceding us. I sure what ever direction you go will be just fine.

[NCMan]

Re: Curing with Insulation or Without?

Two things I'd agree on. Yes, both ways work. And patience is the most important thing. However, unless someone can produce documentation from the insulation manufacturer stating that getting their insulation wet/soaked w/vapor and steam does no harm to it, I'm sticking to drying without. It's never been about whether it works or not. Of course it will eventually dry out, why wouldn't it? But just because it eventually dries out, doesn't mean it's ok to soak it and you don't know if it's long term efficiency has been compromised. I do have to say that I am not familiar w/ceramic insulation, only fiberglass, which I know is not what we all use. W/fiberglass, if it gets wet, it needs to be replaced. Ceramic may be different. I'd need to see some documented evidence that it makes no difference. Until then......

[Greenman]

Re: Curing with Insulation or Without?

It appears that both ways work. It depends on where you are, the tropics with a drying sun will give you a different result than in temperate climes. I did the vcrete over the blanket but had ideal drying conditions and it worked for me.

The slow dry/cure is the go and I did that before the final render coat. The behaviour of the oven (with similar fuel loads) certainly is the best indicator as to how the drying/curing process is going.

All about patience.

[david s]

Re: Curing with Insulation or Without?

yes I get what you say. However the oven dries out with the insulation on.

Now let me paint a different picture of most ovens built on this site.

As per your comments

You dry the oven [no insulation]
put insulation on a dry oven. all ok.

then

a 4" vermiculate layer loaded with WATER over the blanket.
What happens the blanket gets WET and needs to be dried.

Unless of course you are building a dog house then you just poor in dry vermiculate.

The blanket being on simply equalises the temperature throughout the oven I believe preventing cracking. Flame is not consistent and you get hot spots possibly creating movement therefore cracking. Yes taking longer to rid the dome of moisture but it does dry out.

anyway just my 2 bobs [20cents] worth, each to their own. Your way works, and any other method will work it is just about what it is we feel precious about with me it was cracks.

When I did mine [thermocouples in place] I had absolute consistent temperature [10deg difference internal and external brick temps around my dome.

I subscribe to this theory too Colin.As I see it the application of vermicrete really just helps achieve a nice shape covering the lumps and bumps of the blanket. If you want more insulation give the thing an extra layer of blanket. Therefore only around an inch and a half is required to even out the shape and as this is not a particularly deep layer it will dry mostly with sun and wind in a week. A much deeper layer will take ages to dry out. If you really want a deep vermicrete layer then do it in stages and let each layer dry for a week before applying the next layer. I've done lots of ovens this way and found it my best procedure to date.

[NCMan]

Re: Curing with Insulation or Without?

yes I get what you say. However the oven dries out with the insulation on.

Now let me paint a different picture of most ovens built on this site.

As per your comments

You dry the oven [no insulation]
put insulation on a dry oven. all ok.

then

a 4" vermiculate layer loaded with WATER over the blanket.
What happens the blanket gets WET and needs to be dried.

Unless of course you are building a dog house then you just poor in dry vermiculate.

The blanket being on simply equalises the temperature throughout the oven I believe preventing cracking. Flame is not consistent and you get hot spots possibly creating movement therefore cracking. Yes taking longer to rid the dome of moisture but it does dry out.

anyway just my 2 bobs [20cents] worth, each to their own. Your way works, and any other method will work it is just about what it is we feel precious about with me it was cracks.

When I did mine [thermocouples in place] I had absolute consistent temperature [10deg difference internal and external brick temps around my dome.

I also get where you are coming from and respect your opinions. However, just because a person might get their blanket wet, why would they want to hold in even more water by keeping the interior water trapped in by the insulation? Again, not saying either is right or wrong and we all have our own opinions. I do, however, stand by my line of thinking. Also, I don't plan on getting my insulation wet, if I can help it. When the intention is getting the water out w/drying fires, etc., I just don't see where any method of holding it in serves any purpose. Again, that's just me.