Longmont, CO new WFO build - casted over sand

[cnegrelli]

Is it ok to use galvanized wire to hold down ceramic blanket (on outside)?

[SableSprings]

Yes, galvanized wire works just fine. I've used both chicken wire and metal lath--both inexpensive and relatively easy to cut & work with. (My assumption is you mean to use a mesh wire not just a single wire to weave back & forth...) Make sure you use a good breathing mask, eye protection (swimming goggles or the no-cry onion glasses work really well), and gloves while cutting and applying the blanket. It doesn't hurt to wear an old long sleeve shirt that's bound for the dump. If it's hot & muggy when you are working with the ceramic stuff, it can make you pretty itchy. Also make sure to keep kids and animals away from the ceramic blankets while you're waiting to cover your finished dome.

After placing, cutting, & fitting the blanket(s) over the dome, it's helpful to try and cut the wire and tie it together as closely as possible over the ceramic blanket (& final the dome shape you'd like). When you put on the base render layer for your stucco, it's nice not to have the wire mesh bouncing around...

You might find it helpful to secure the bottom ends of the mesh to the concrete oven base to help you hold & stretch it while you use pieces of wire to tie it together in place. Don't worry about overlapping or cutting wire mesh sections/pieces too precisely...the wire is just to hold the blanket in place and provide some base structure for the next masonry layer...which covers up any ugly wire work.

p.s. - plan on a first cool, then long warm shower after you've stripped off your working clothes (outside!)...cool keeps the pores closed so soap & rinse takes off any loose ceramic fibers instead of directing them into wide open pores.... Don't stress on this, it's just worth thinking about a little extra protection & cleanup.

[cnegrelli]

I don't plan to apply a render as I'm building an enclosure, so just some wire crisscross to hold it down. I will down a couple layers at least as I have a lot then end up filling up the enclosure a bit with loose vermiculite.

Excellent advise on the cold shower. My wife is also advocating those for me.

[cnegrelli]

I've resisted the urge to barge ahead on this build and will take today to re-hydrate the oven and attempt to patch the couple voids. The Temp dropped today from 96 to 66 for a high, and the humidity is up a bit. So I've currently got both the inside and outside of oven wet, completely covered with a tarp. I also wedged a wet sponge up against the two areas of interest. Will try to keep it very wet for the next few hours, perhaps even overnight, and give it a go.

Delays my tribal need to start some fires..... I've got some other things to do that are all minor and cosmetic, while I'm pumping water back into this oven!

[cnegrelli]

So with the Relative Humidity at 78% yesterday (vs. the 15% we had been seeing, I got some moisture on/in the oven and was able to patch up a couple voids I had found and it seems like it took ok. Will leave covered and moist thru today.

I also mixed up some v-crete and created my thermal break / expansiion joint between the dome and gallery. I used some Ceramic Rope I bought on Amazon that I wedged into the seam, covering from above and below with V-crete. Seems to have hardened up nicely this morning.

Question: I've made a bit of a mess with the v-crete and refractory patching on my floor bricks. Can I give them a light sanding with a portable angle grinder or hand sander? I searched and found some threads but didn't really see the definitive answer on this. What to use for sandpaper or better yet, pads on grinder? Looking to just clean them up, maybe take off some share edges here or there.

[SableSprings]

To clean up, just take the side of your trowel and scrape the floor brick spots...it can be pretty easy to take off "new" mortar materials spilled on the floor bricks. Grinders can get away from you pretty quickly and I think it would be an overkill tool for this job. I suspect a little sandpaper and elbow grease will be quite quick and effective as would a stiff wire brush after the scraping. Another option is to use a chisel and some light tapping with a hammer--that should pop most anything off the cooking brick surface that won't come off by scraping. You don't have to get the floor bricks pristine...if you can't scrape it or pop it off with a little chisel work then it's not going to come off with your pizza. Your goal is really to make it smooth enough that your peel doesn't catch on it. Note that some of the mortar "white" can also be removed with a little household vinegar and a stiff brush.

Hope this helps...

[cnegrelli]

Will try the stiff brush method as it's really just stained from Portland.

I got in the bunny suit and did my insulation blanket today. Same brand as Russel had used , but mine was foiled on both sides. The foil came right off, so no problem there. It was 2" and I did three layers. The last one required I use some smaller pieces.

Because I didn't cut the insulation board and firebrick floor exactly to the shape of the dome, it has a jagged bottom circumference. This keeps me from snugging the blanket up to the bottom.
Because I'm building a enclosure, I will fill the bottom well with vermiculite. I hope that's a good plan.

Do folks who build an enclosure ever render over the blanket? I'm tempted just to have that nasty stuff covered and sealed.

[cnegrelli]

Render or not?

[fox]

I rendered mine but left a 4" hole in the very top to allow moister to exit when drying out the dome with small fires, I have plugged the hole now & painted over the whole thing.

[UtahBeehiver]

Since you are enclosing and adding dry vermiculite, your labor resources might be better spent on other aspects of the oven. Your oven is really insulated well. FYI, you can drill some Tapcons into the hearth to fasten your wire to hold down the CF blanket.

[SableSprings]

I think that you need to think about how long until you will have this enclosed. Turns out squirrels, mice, & birds love to pick out fibers for their nests. As Russell noted, since you are enclosing and adding vermiculite there are other jobs that should have higher priorities...but that assumes you are going to get your enclosure built & filled & closed soon .

As for venting, I don't think you need to worry about it since your enclosure will probably have a built-in screened soffit or two and that will keep out the rodents and let any moisture escape. Looking good on having curing fires pretty soon (if you haven't already ).

[cnegrelli]

Since you are enclosing and adding dry vermiculite, your labor resources might be better spent on other aspects of the oven. Your oven is really insulated well. FYI, you can drill some Tapcons into the hearth to fasten your wire to hold down the CF blanket.

I have lots of wire crisscrossing the outside of the insulation as suggested. But I do have a massive squirrel problem. By the way, I left the gas can out last night, and they ate thru the plastic spout on it. Unbelievable.

The enclosure is a total PITA, as it's a complete octogon. Not like Octoforno, but simliar (picture posted in this thread earlier). I'm struggling with how to frame some of the tidbits, but I think I will just have to do it. The gallery area ended up bigger than I had planned, so I'm trying to not make the enclosure bigger than I need to.

I am trying to jump on the enclosure part, as my wife wants to see that done asap. Really the whole reason I went with cast vs firebrick build. Her tolerance is waning thin after just a month or so. The good news is she is not a shopper, but that's also the bad news!

I think I will start with a slow and low curing fire tomorrow with some lump charcoal from my smoker.

[cnegrelli]

I think that you need to think about how long until you will have this enclosed. Turns out squirrels, mice, & birds love to pick out fibers for their nests. As Russell noted, since you are enclosing and adding vermiculite there are other jobs that should have higher priorities...but that assumes you are going to get your enclosure built & filled & closed soon .

As for venting, I don't think you need to worry about it since your enclosure will probably have a built-in screened soffit or two and that will keep out the rodents and let any moisture escape. Looking good on having curing fires pretty soon (if you haven't already ).

No soffits. It's really an octogon shape. 3D. Just like a dome is half a sphere, my enclosure is half of a complete 3D octogon. We will see!

[cnegrelli]

[cnegrelli]

Finally can start doing some fire today. Casting has been dried out fo a few weeks now, just haven't had any time.

david s the link you sent me for Refractory suggests: Firing

A slow fire can be applied and the temperature raised at the rate of 50șC approx per hour per 25mm thickness of lining until working temperature is reached.

For 50mm, does that mean, half that rate or double that rate?

I'm assuming since it's about 30 degrees C outside, I can take it up 50șC, every two hours (half the rate).....