Motar falling out - help !

[Sidcup1]

Just started to cook regularly with my completed oven, it has been cured. After about 3 pizza sessions I have noticed what looks like cracks but they are actually along the joints - the mortar between the bricks on the inside of the oven is falling out/disappearing. I used a polystyrene dome to rest the bricks on whilst building, so I couldnt point the mortar on the inside properly. But what was there is clearly now missing.
Is this a problem ?
Can it be ignored or does it need repointing from inside (gulp) ?
More pics available but couldnt load more than 1.

[SableSprings]

Did you use homebrew for your mortar? Not getting mortar into the inner edge of the dome bricks is not a fatal error. Once the dome has been completed, the structure is incredibly stable (even without mortared joints). As long as you are not getting chunks of mortar falling onto your pizzas, , I don't see this as a problem...or worth pointing. I suspect your mortar was a little too dry when applied or you just didn't butter the bricks with enough on the inside edges. Again, once the dome is closed, the mortar is more extra mass than it is a crucial structure requirement.

Did you apply an outside insulation layer of ceramic batting or a 10:1 perlite/vermiculite:cement layer over the dome? Over the insulation, did you stucco? An outside pic of the oven would be good. (p.s. if your pictures are over 1.5 MB they will not upload...try getting a free program like FastStone Photo resizer to reduce the pics...800x600 pixels will produce a good quality photo right around 100 KB - more than 10x smaller).

[Sidcup1]

Thanks for the reply Mr Sablesprings, I was a bit worried. This has taken me over 4 years to complete and rather disheartened to think that that could have been the start of the end !
I used homebrew, cant remember the mix as I did it 3 years ago, but it was recommended on this site. Fireclay lime sand and cement. ....and some water.
After the bricks was between 0.5-1 inch of the homebrew mix applied to the back of the brick dome to add to the thermal mass, then 3 inches of the insulation blanket, an efficient one I recall. Then rendered (Stucco) about 1 inch thick and over that an epoxy resin based tile adhesive thinly spread to waterproof the dome, then about 15000 1penny coins stuck with ‘No Nails’ adhesive, and grouted with a brown epoxy resin grout. This gives a copper colour which ironically was the cheapest way of doing it as copper tiles were pricey !
The dome gets hot in the sun (we have a heat wave at the mo) but not hot from the oven.
The top of the oven is vented with a removeable endcap for a copper pipe.

[UtahBeehiver]

That's a lot of pennies... I agree with Mike, that the domes are self supporting. I did copper tiles, which I made myself and my material cost only was $800.

[Sidcup1]

Thanks, just seen your pics, love the copper. I chose it as it kinda goes with the garden and doesnt look too out of place, not in Autumn away ! Did you treat or spray your copper ? I am going to stay mine with Incralac.
Also your door looks great, stainless steel I take it ? Are there any problems with it at high heat ? Did you put a seal on it ?

[SableSprings]

Sidcup1 - Your oven looks fabulous! We have friends in Canada that have been looking at putting a Gaudi style tile finish over the existing stucco. I'm going to show them your oven and suggest (since Canada no longer uses pennies) that they think about doing their oven recovering in your style

I had the experience of working with an old Napoli (low dome) style oven in 2014 with some friends celebrating their 50th anniversary at a VBRO in Sorrento, Italy. The oven was built into a hillside above the house and I thought you would appreciate the pictures (as related to your mortar gaps).

[UtahBeehiver]

I did not treat the copper and letting it naturally age, it is starting to get some green tinges to it. My door is stainless steel stuffed with CaSi board, no seal, but fits pretty snug. No problems with warping or high heat. If I were to do it differently I would make the door slightly thicker to accommodate a little more insulation.FYI, SS is still fairly conductive but certainly better than carbon steel or aluminum.

[Gulf]

Very nice!

"Penny Lane"

[shanxk8]

Hello Sidcup and Sable,
We're located in Canada as well, and just had the thought of covering our dome with pennies. To our surprise, this came up with some very nice examples on a google image search. But our concern, having talked to a few people that do indoor & outdoor work with tiling (& other things) is that their guidance would not be to do pennies or epoxy. The think that the epoxy will crack under the cold temperature (or big temperature changes).

Did you Canadian friend cover their dome with pennies? Sidcup, how is your epoxy & pennies standing up?
Any guidance on where to look for epoxies suitable for outdoors with freezing temperatures in winter?

Thanks in advance,
David

[SableSprings]

David, our friends in Canada have decided to build a small enclosure over their oven...primarily because tarping over the extreme winter weather conditions has not been very reliable. When we talked about doing pennies it was with the thought of using silicone adhesive. The low end temperature range is really good (down to -75F/-59C for basic silicone adhesives) and there are some silicone products that are rated for lower temps...
(but I wouldn't consider living in those kind of conditions ). The silicon provides a little flexibility, but no real lateral strength...but it's only a penny right?

We liked the concept of using dabs of silicone on the penny, then pressing each in place. A true pain in the a** in some ways, but giving the ultimate control of placement and "do it at your own pace" advantages. Mostly my concern was, since Canada no longer has pennies...can you just go into a US bank and buy more than a couple rolls at a time or would you be able to place and order for a large batch at a time.

If it was me, I would recreate the current outer render on a board or rock and do a test section. I know it would take going through the next winter...but the thought of putting all those pennies on and then coming back the next spring to find all piled up around bottom perimeter would be just too painful...

I hope Sidcup comes back with a report on his epoxy version. Keep us all posted on what you're doing.

[shanxk8]

I think I will do some research on the best epoxy for outdoors. My wife is confident you can still but boxes of pennies.

My waterproofing with flex Crete before the winter send to have done very well. I'm pleased with it so far. Here's a pic of the oven covered in snow. No steam coming out my vent as I fired it over the winter nor now that the snow is gone.

[shanxk8]

Perhaps the silicone adhesive would be something to look into to adhere them, but could it be also used for a covering layer? We are thinking to cover them like you'd do for a penny floor.

[Sidcup1]

Sorry re late reply and update..

I used Mapei Kerapoxy adhesive to cover the rendered (stucco) shell, which waterproofed the whole dome nicely. Then pennies stuck using a ‘no nails’ (grab) adhesive so pennies didnt slip downwards, then grouted with Kerapoxy grout, cleaning pennies with Kerapoxy grout cleaner as I worked. The pennies (75% shinney) were sealed with Incralac.

Two years on...

No cracking of epoxy, we have had temps between -5 to 37 deg C (today is the hottest incidentally!). The pennies are still (reasonably) bright and shinney.

I hope this helps....

[hughjamton]

Perhaps the silicone adhesive would be something to look into to adhere them, but could it be also used for a covering layer? We are thinking to cover them like you'd do for a penny floor.

Silicone wouldn't be any good for sealing the coins, clear silicone will become discoloured very quickly.

[shanxk8]

Hi Sidcup, thank you very much for sharing how you've done it. Glad to hear the idea has worked for someone else already. At this point in the year, this finishing project will likely need to wait till next spring. Freezing temps overnight are coming pretty soon for us unfortunately.