cure questions

[waynebergman]

My supplier was telling me for the castable product I bought from him likes to be cured at about 175 degrees for 8 FULL HOURS. I was planning to go with a 7 day cure staging as described in out insruction manual from this site so wondering how this suggestion from my supplier will fit into what is normally done by oven builders on this site. I could do 100 degress the first day and then 175 the next but let it burn at this temp for 8 hours and then progress onto the 300 degree etc stages. So not real sure how to treat this castable part of my oven, if I burn a long time at 175 degress not sure if that is a no no or not.
Also I plan to put my blanket insulation on after first cure so I can see cracks etc so if I understand it right if I do this I will be putting my vermiculite concrete over top of blanket and then I will need to also let the sit for a week and then cure it also. Would the curing of the vermic layer need the full week before the cure and then then slow methodical heat up times over small increments or how would this second vermic layer need to be cured....thanks wayne

[Acoma]

Re: cure questions

Wayne, it is the completion of the dome, waiting a week, then slowly curing each day with 100 degree increases. Each time you reach the temp, let it slowly come down. Once done, evaluate the cracks, should they exist. Repair if needed, then continue on with the vermic if that is the route, post blanket. If during curing stage, like Ken's, you want the blanket on, then do so, you will be of the few having done so this way. Nothing wrong. Nice to see you progressing. You are right not to go straight to 175 for 8 hours.

[waynebergman]

Re: cure questions

Thanks Acoma...still not sure here about one thing.After initial curing i put on blanket and vermic concrete...Yes I get that but what I am not sure about is do I need to cure the vermiculite concrete in the same way after it has been added to the equation. Also I will be putting on Type N mortar and river rock on top of vermic concrete. I am guessing I dont have to cure this vermic layer but thought I should check....thanks wayne

[Ken524]

Re: cure questions

what I am not sure about is do I need to cure the vermiculite concrete in the same way after it has been added to the equation.

Wayne,

There really won't be any way for you to "cure" the vermiculite layer with heat. When your oven is super hot, the vermiculite layer will only get warm. Those blankets do an excellent job.

I have about 3" of blanket on top of my dome. When the dome is turning white the topmost blanket is cool to the touch.

[Acoma]

Re: cure questions

Wayne, you do not need to cure the same way with vermic as to the dome. You may recall that you are driving out moisture over time. Main thing is driving out the moisture from the dome. Because you are applying mortar over vermic, which will likely be moist to maintain its shape before applying the mortar, you will have lots of moisture to drive out over time. It will take time before full efficiency is maintained, be patient for that. Start with the 7 day cure for the dome, 100 degree incriments, then slowly let it come down. Then go to the next step.

[gjbingham]

Re: cure questions

Wayne,
I agree with Ken. If you have more than 1 inch thickness of blanket on the dome, the heat does not seem to transfer to the vermiclite insulation layer at all. With only one inch, I would recommend giving the vermicrete at least 3 days of curing before getting your oven really hot.

The real answer may be that no one really knows exactly which way is best. Being gentle with your early applications of heat is probably the best advice.

George

[waynebergman]

Re: cure questions

Thanks guys....is there also a bit of cure time after vermic layer before I apply the type "N" and river rock. Also I am woondering after vermic layer is on can I move my canvas shed out of the way. Not sure how well the vermic layer holds up to rainy days etc before I get my type N over top of it. I plan after the vermic layer is done to move the shed and start using the oven and just take my time with the river rock treatment if the wheather wont bother things. It will be nice to get cooking and put away the saw and bricks and all my mess out there and then just tinker away at the cosmetic part of the build........thanks for the help folks....wayne

[CanuckJim]

Re: cure questions

Wayne,

I wouldn't move the shed over the oven. The vermic layer is a good insulator, but it's also a great sponge. You won't be able to expose it to the elements until you've parged with Type N, but that does not mean you can't fire the oven in the meantime.

Jim

[waynebergman]

Re: cure questions

Thanks Jim, is there a waiting period after the vermic layer is done before I parge it with the type N.....wayne
Your oven in the snow pic looks awesome.

[CanuckJim]

Re: cure questions

Wayne,

I'd keep it dry for at least two weeks before parging. The parge coat really won't be completely cured for 28 days. After that, you could go ahead with your mosaic approach, but you'd have to wait another 28 days before you could seal it (like mortars, etc., the sealant can't be allowed to freeze; otherwise it will turn white). To be on the safe side, I'd expose it to the elements only after it has been sealed. I'd just be patient about the covering; maybe move it when you want to bake, and put it back in place when the oven is not in use.

Jim

[waynebergman]

Re: cure questions

Thank you Jim this is exactly what I need to know here. Appreciate it muchly...wayne

[david s]

Re: cure questions

When adding the vermiculite insulating layer you also aadd lots of water. Who knows how much of this will evaporate ? not much is my guess. One litre of water makes 1000L steam ! My suspicion is that steam pressure is responsible for cracks in the outerlayer (for igloo style construction) I now do two layers of newspaper between the vermiculite and the outer shell which should provide a small space for steam to escape through a hole left in the outer shell which can be plugged after quite a few firings. You can feel the damp newspaper layer in this hole even when you think the oven is dry. Wet insulation does not insulate well either.