36" in Chapin, SC

[hubert_s]

Re: 36" in Chapin, SC

It has been a while since I have posted here. There were a lot of delays in the construction of our house, and the pizza oven was no exception. I pretty much left it alone after completing the dome last summer.

A couple of weeks ago I finished the entry and put the vent in place. I started with curing fires last Tuesday and a mortar joint in the arch opened up right away. It was initially only a hairline crack, but has opened up quite a bit at higher temperatures. Otherwise, there are no cracks that I can see. I am hoping to bake some Zwiebelkuchen (German onion pie) and pizza this weekend.

I am a little concerned about the arch crack, though. When the oven cools, the crack always closes, but opened up to about 3mm in the front and to about 1mm on the inside of the oven when I heated to 600 degF. I think if I grind out the mortar and pack new mortar back in the joint, it will just crack again when heated.

If anybody has a good idea how to fix it, please let me know.

[NCMan]

Re: 36" in Chapin, SC

Is it possible to see a photo or two? That would help to understand where the crack is and what may be the cause. But, you are most likely correct in your assumption that it will reappear.

[hubert_s]

Re: 36" in Chapin, SC

I will take some pictures of the crack next time I fire the oven.

[hubert_s]

Re: 36" in Chapin, SC

I checked the oven this morning and the crack did not close up after the last firing. I have attached a photo of the crack and a picture of the smoke coming out of the chimney from the first firing. The chimney really draws well.

The gap is now about 2mm wide at the front. Inside the oven, the gap narrows down to almost touching. I put a light inside and could not see through the gap along its entire length, so I think there are some small pieces of loose mortar in there now that prevent the crack from closing like it did before. There is a hairline crack on the inside one row up and one brick over in the vertical direction. I could not get a good picture of it.

I searched the forum for similar cracks and how people dealt with it. There have been a lot of different fixes tried out (mortar, different varieties of furnace caulk, Insulstick), but I could not find any long term reports of what worked and what didn't. If anybody has patched a similar crack and it has held up, I would very much appreciate if you could let me know what you did.

[hubert_s]

Re: 36" in Chapin, SC

I did another curing fire last night, up to around 700. The crack seemed to widen a little bit more. I am still looking for ideas how to fix it.

I used the heat of the curing fire to bake a couple Zwiebelkuchen and they turned out really good, see picture below. This is a German recipe from Swabia with onions, bacon, cream, quark (German dairy product similar to Greek yoghurt), eggs and a little potato for the topping. The dough uses milk instead of water and has a little butter in it.

I think the oven is ready for the main event and I will start a batch of pizza dough tonight to have it ready for the weekend. On second thought, I will start two batches of pizza dough tonight to have them ready for the weekend. I don't have a long handled peel, but I think I can get the pizza in the oven with my old wooden peel and a welding glove. I have to fabricate some sort of long handled turning peel before the weekend, though. I think I might just mount a broom handle to the 8" disc I cut from the vent before welding on the chimney collar.

[NCMan]

Re: 36" in Chapin, SC

From what I can see, there isn't a whole lot you can do about the crack, as far as fixing it. It most likely will do no harm and will be just an issue of aesthetics. What I would try, is to clean the area as best you can and take a shot at mixing up a bit of refractory mortar, using small grain sand and try patching it w/that. Really pack it in there tight. It may or may not stay there, but it's worth a try, in my opinion. If it does stay there, it would look a lot better, since it will match your other mortar. If not, clean it out again and try some high heat caulking. As I said before, there really is no fix, just methods of trying to find a way to hide it. Perhaps others will offer up some remedies that they have used. This is simply what I would try, basing it off your photo. You also may want to hold off a while until you feel it has stopped widening. Good luck w/it.

[hubert_s]

Re: 36" in Chapin, SC

Thanks for your suggestion, NCMan. I will definitely wait a little while before attempting a fix. Partly to make sure the gap is as wide as it is going to get like you suggest, but more so because I want to use the oven. I am going to Tokyo for 10 days in late May and will try to fix it just before I leave.

I found a thread here that suggested grinding out the old mortar to open up a 3/8" gap and then pack new mortar into the gap. I will probably try that unless somebody has a better suggestion.

[david s]

Re: 36" in Chapin, SC

Attempting to repair cracks in kilns and ovens is invariably only partly successful at best. Some things that will help are
1. Dampen the area around the crack first and wait around 10 mins for it to penetrate.
2. Make a thin paste of water and cement only (either calcium aluminate or calcium silicate, whichever you are using) you can simply sieve out the sand in the mortar to get this.Apply this mixture into the crack with a fine paintbrush.This step is like a primer to aid the bond with the mortar and the refractory.
3. Then fill the crack with the mortar mix, this time with the sand in it (peanut butter consistency) forcing it in hard.
4. Cover the repaired crack, if you can, with damp sand to prevent too much water loss from the mortar for curing.
5. Leave it for a week before firing.

[NCMan]

Re: 36" in Chapin, SC

I agree w/all of the above, except I would not remove the sand. I feel for a joint/crack of that width (judging by the photo), you may want to have some fine sand in there. If it were smaller/narrower, then I'd perhaps skip the sand. Just my opinion, that's all. To keep it moist afterwards, you could tape some saran wrap/plastic, etc. over it when done and try to keep it shaded, to avoid it drying too quickly. Also, it may be tough to fill that crack w/a paint brush. I'd suggest a small kitchen sponge. A cheap throwaway. After you are done w/it, you can rinse it out and use it again to clean up around the repair area. But, whatever you have handy and works for you. Best of luck to you.

[hubert_s]

Re: 36" in Chapin, SC

Thanks for all the details, David and NCMan.

I think David meant to leave out the sand only for initially painting the faces of the bricks and then use regular mortar with sand.

The oven is under a covered porch, so shade is no problem. But it does get hot here, I think it was in the nineties yesterday.

Should I remove the old mortar before attempting the repair? The gap is about 3mm in the front and 1mm in the back. I thing it would be difficult to get in there even with a small paint brush. What is the best tool to get the old mortar out?

[david s]

Re: 36" in Chapin, SC

Thanks for all the details, David and NCMan.

I think David meant to leave out the sand only for initially painting the faces of the bricks and then use regular mortar with sand.

The oven is under a covered porch, so shade is no problem. But it does get hot here, I think it was in the nineties yesterday.

Should I remove the old mortar before attempting the repair? The gap is about 3mm in the front and 1mm in the back. I thing it would be difficult to get in there even with a small paint brush. What is the best tool to get the old mortar out?

You're on your own there. I'd probably try just filling the cracked bit rather than removing all the mortar, as it's probably adhered well on the other side. Do what you think is best.

[NCMan]

Re: 36" in Chapin, SC

I agree. I'd be more concerned w/getting the area clean than getting the old mortar out, unless it is loose.

[Gulf]

Re: 36" in Chapin, SC

Thanks for all the details, David and NCMan.
..........The gap is about 3mm in the front and 1mm in the back. I thing it would be difficult to get in there even with a small paint brush........

Your'e getting some great! advice, I would just like to add this:

For this joint, I would get a 1" steel putty knife (not a scraper) and a disposable 1" plastic putty knife (the plastic knife will be thicker). Put a small amount of mortar into the face of the joint and quickly poke it from the front to the back. It will take several strokes and then reapplying mortar to get any amount of mortar packed in the back of the joint with the thin blade. But, it will start filling from the back toward the front. At the rear of the arch, near the bottom, you may have to place a finger behind the crack for a temporary "back stop". As your pointing gets nearer to the front, where it is wider, you can switch to the thicker plastic knife. You can substitute any blunt ended thin tools that you may have laying around for the knifes, as long as they will fit into the crack at the depth that you are working.

[hubert_s]

Re: 36" in Chapin, SC

Thanks everybody for your suggestions, I will report back after I attempt to patch it.

In the meantime, we had our first pizza party last night. It was really nice to see the dome clear for the first time and to see the engraving in the keystone again. I have attached a picture of the first pizza margherita in the oven which I forgot to take a picture of after I took it out. The second pizza was a spinach, pine nut, feta and mozzarella pizza and I remembered to take a picture. I made a total of six pizzas. The first one was a little overcooked at the bottom, one might even say burnt. The second one was better and the third one pretty close to perfect. I never had any luck with the Caputo flour in the electric oven, but it was really great from the wood fired oven.

My wife has already booked a pizza party for next weekend. I would like to build some sort of oven door before then. Yesterday evening I just put some bricks in front of the opening and the oven was still above 500F this morning, but moving the hot bricks around is a bit inconvenient. I also have to improve my oven tools a bit or my technique or both. Getting the pizza into the oven was no problem with the short handled peel I used to use with my pizza steel in the oven. For a turning peel I just mounted the cut out from my vent to a four foot handle and I had some trouble getting under the pizza because of the bump where the handle is mounted. We'll see how much time I'll have to work on the oven during the week.