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Finally getting to building WFO in Calgary, Canada

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  • mongota
    replied
    No maintenance with the Thoroseal/Masterseal.

    I have a 42" diameter dome covered with 4" of blanket insulation and maybe a 3/4" to 1" thick stucco render over the insulation. I weighed out 12-1/2lbs of Thoroseal powder for each coat and mixed it with latex admix and water. It gave me the perfect amount of material for each of the two coats. Zero waste. I used half of the 50lb bag.

    The directions will tell you to do a thorough initial mix to a loose consistency, followed by a 10 minute slake. Follow those instructions. I used a small mixing bar on my cordless drill, and remixed it several times while applying to loosen it up. It can stiffen up in the bucket when left alone, but as soon as you hit it again with the drill, it loosens up and flows like pancake batter.

    I painted it on with a masonry brush, a standard brush, mine is from Marshalltown. Went on fine. When I got towards the top of the dome I just dumped a bit of it on the dome and schmeared it all over with the brush, that was faster. Work it into the pores, then a quick back brush, then leave it alone.

    It helped to moisten the dome prior to applying it. If you apply it on a dry dome, it can seize up as you brush it on.

    I'll be adding a vent pipe in my dome as well. I have the threaded pipe and cap. Should have done it already, but I forgot about it.
    Last edited by mongota; 08-03-2018, 08:58 PM.

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  • shanxk8
    replied
    Thanks for the suggestions on waterproofing Mongo.
    I've already done my curing fires, but suspect I will still be driving moisture out due to rain and snow.
    I also plan to include a breather vent at the top of my dome. I will look into thoroseal. (Search tells me it's called MasterSeal 581)

    Is there maintenance to keep it waterproof? Do you really after a certain period like a paint?
    Last edited by shanxk8; 08-03-2018, 07:28 PM. Reason: words

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  • mongota
    replied
    I'll chime in regarding RedGard...

    I used it on my slab, between my slab and the board insulation.

    I do NOT recommend using it on the stucco layers over the dome.

    I think you always have to plan on moisture getting in to the oven some way, some how. As a result, you need a safe way to clear the dome of moisture.

    RedGard isn't just a waterproof membrane, it's also a vapor barrier. If the dome was encased in RedGard, moisture drying fires could drive the moisture into the insulation and then into the stucco. When the moisture hit the RedGard, it'd be trapped. Trapped moisture, plus added heat from the drying fire? The insulation and stucco could then become hot because of the trapped moisture. The "rubberized" Redgard could then overtemp and stank the place up.

    I used Thoroseal over my stucco as a waterproof coating. It's cement based, and it's vapor-permeable. So it resists liquid moisture, but allows moisture vapor to be driven through it by drying fires.

    If you want a liquid-type membrane similar to RedGard, look at Laticrete's Liquid Hydroban. It's a waterproofing membrane, but unlike RedGard, Hydroban Liquid is a vapor permeable membrane.

    If I had to pick one...which I did, lol...I'd choose Thoroseal because it's a cement-based product, not a "rubber membrane" type of product. And it's vapor permeable.

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  • UtahBeehiver
    replied
    I not sure what gauge SS I used and I do not have a mic. but it is fairly thin. Notice that the welds, done with a tig, are not continuous but at intervals. This is was done to prevent warping during the welding phase also allowing for some expansion. If I were to do again, I would make the cavity a little deeper for more insulation, IE 2" instead of 1.5". Too deep and the doors get heavy fast. I normally place the door on the oven after a pizza party with the interior temp. abt 600-650 so hot but not blazing hot.

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  • shanxk8
    replied
    Thanks Russell. Do you have an idea how thin of SS or steel will still hold shape with high temps? I plan to make all from the same gauge (both sides and back facing the oven). I actually plan to make the front from wood, also bolted on such that it can be replaced if needed. My friend experience in welding indicated that shape issues would be more prevalent with welded due to cracking at corners due to thermal expansion/contraction. His suggestion is to create slots at the outer surface hole to allow for expansion/contraction of on surface relative to the other. I am leaning toward this option as it would allow me to build at home without welding.

    From local home reno store there are options for 16G, 22G and 26G for carbon steel, more options for that & SS from the "metal supermarket". My thought is 26G is too thin, and my hope is 22G is adequate. I like the suggestion to search for scrap from BBQ or fridges, i may have to see what the internet (kijiji) contains before i go purchasing.

    On #3, will have to follow-up with one. I was hoping someone that had worked with granite might have insight before i head there.

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  • UtahBeehiver
    replied
    1. Carbon steel has a K value (thermal conductivity) of 43 vs SS of 16, in perspective CaSi K value is 0.50-55. Aluminum has a substantially higher K value than even carbon steel. Some builders have been using wood to seal chambers at lower temps. Pro, lower thermal loss, will scorch at high temps. If your welder friend can weld SS (mig or tig) IMHO that is best. Get as thin as possible yet still hold shape. I found you can find scrap SS, from old BBQs or refrigerators.

    2. no comment, never used

    3. I would ask a counter top installer.
    Last edited by UtahBeehiver; 08-03-2018, 07:10 AM.

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  • shanxk8
    replied
    I have a couple questions for the forum, as I'm doing more thinking and less work on finishing the oven at the moment.

    1. Insulated door, I need one now that we're trying to cook more frequently: trying to decide if metal door with CF blanket insulation inside should be made from stainless (original thought) or plain carbon steel. A friend familiar with wedding and metal suggests I actually build with bolts and no welds. So now I just need to figure out what material to buy.
    How have people's metal doors held up when made with carbon vs stainless steel?

    2. Have read about people using redgard. I unfortunately didn't put it under v-crete insulation, but am thinking it may be worthwhile to put on the remainder of the hearth to keep moisture from getting into concrete. Would this be worth it? I also had a thought, can redgard be used in between the layers of stucco, to help with waterproofing?

    3. As I cut granite I am getting cuttings that I've started to collect. Could these cuttings be used instead of the colorants you'd but to mix with the epoxy? (This is for vertical joints between granite pieces)
    Also, does anyone have suggestions on a good granite epoxy to use for joining countertops?

    Thanks,
    David

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  • shanxk8
    replied
    Hello all, it has been a little while since i posted. In that time we've had a couple of successful pizza bakes. The most recent was 10 or eleven pizzas for a large family gathering.

    Recent progress has been slower, with more insulation layers installed on the dome and some more brick work complete to cover the concrete blocks.

    I've since run out of matching bricks, so have moved on to cutting the granite pieces to create the counter top before applying stucco to the dome.

    The lastest pics were after the insulation and most of that brick work was done.

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  • shanxk8
    replied
    We got to cook the first pizzas in our oven two nights ago, and they were amazing.

    Funny story, as my wife and father were home to start and tend to the fire while i was still at work. When I was leaving to go home I asked how it was going. I she told me the oven was about 600 degrees after 2 hours. I was worried the insulation got wet in a thunderstorm the day before. I measured the temp when I got home, 660. Fire was burning well and the dome was clearing. After a few minutes of worry, I realized my dad had the thermometer set to C rather than F. Top of the dome was a happy 1100+F and the floor was 800+F.

    Cooking went smoother than I expected and the pizzas were delicious.
    Thank you all for your help getting me this far. Lots still to do with cosmetic finishes but I've achieved the main goal!

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  • SableSprings
    replied
    So now comes the hard part...deciding whether to invite friends, relatives, or to just hunker down and enjoy the feast and wonderful bounty coming from your WFO. Nice build and looks like your cure is pretty much done, onward and upward

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  • UtahBeehiver
    replied
    Dome is clearing nicely so your cure is working well plus you are getting some nice meals out of it.

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  • shanxk8
    replied
    So the last fire over the weekend was to cook another meal, chicken this time (yum!) After running for a while (hours) at 4-500F and cooking, i'd planned to up the temperature a little higher than the last fire, so put in a couple more pieces of wood (~1.5" square, scraps of 2x4 halved lengthwise). When i went back later, the oven was over 900F at the top and starting more than 1/2 clear. Not long after most of the dome was clearing, so i just left it and let it go. The floor was over 600F also.

    By the end the entire dome was clear, and inspectin gthe next day didn't see any cracks. My hope is that the upper dome that was built in 2018 was getting dry, and the lower dome built in 2017 had long since cured. Later this week, we may have to try getting up to the 8-900F and get the floor over 700F

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  • UtahBeehiver
    replied
    The tarp over the oven is an indicator that water is turning to steam if you see it during a fire, you can remove it periodically, then back on to check again. The inner surface may be reaching this temp but it does not mean the bottom is seeing the same temps. Like I mentioned it takes time to dry out floor pcrete.

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  • shanxk8
    replied
    A couple fires back i was seeing moisture under the tarp. I folded it back while firing for the last few (oops) as i thought i wanted it escaping rather than being trapped and going back into insulation and then bricks. Maybe i will leave it partway covering (half?) the oven so i can see if moisture is collecting.

    I had thought that getting bricks up to the 5-600F level means that i'd pushed most of the water out. Similarly, i'd thought the floor getting up to 4-500F meant the pcrete was getting more dried out. (Maybe that is just the middle, but edges of pcrete have moisture -thus lower temps at outside of the floor.

    This weekend i'll have to try for a longer duration burn to a 5-600F temperature to get the oven saturated with heat, to see how that works right now.

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  • UtahBeehiver
    replied
    If you still see moisture under the tarp as you fire it means there is still water in the brick/insulation. With each firing the oven will perform better. Again, it is not the time to rush the curing process and you can still cook something as well. The dome will clear (black soot burns off) in the 900 F range but you are not there yet in the curing process. You mention in a earlier post that the pcrete may have gotten wet as well. This area takes a long time to drive the water out.

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