30" Cast Scotland

[Daveholdn]

No, fit it that way, you’re good to go. Just make sure the pipe is not a really tight fit, so there’s a little room to allow it’s expansion within the casting.

This is the way I do it, but there are plenty of other solutions no doubt.

Aye that's what worried me a little david s, I did pack cardboard around my 150mm flue mold at casting stage as thought it would leave it a little loose for the expansion, but my flue is actually quite a tight fit unfortunately, would you recommend trying to lightly sand the inside of the flue cast a little to try and make it less of a tight fit?

Cheers again

[david s]

If you can rotate the pipe within the casting reasonably easily then it'll be ok.

[Daveholdn]

Ah gutted, even left my arch for a couple of days longer just in case. I think the problem is I used my decorative glass as my gravel for the mix, it's really smooth stuff so I don't think it binded. My mix was 1 cement:2sand:3gravel(decorative aggregate). Has anyone had anything like this, or should I have put rebar through it?
Cheers again.

@david s, thanks for the flue advice there, it does rota te so all good to go, just gotta get this arch sorted first

[Mullster]

So sorry to see that mate - perhaps it was the aggregate like you said. At least you can make another one though.
I used some reinforcement in mine and just put the decorative on the very front (set in) and used normal pea gravel in the mix.

[Gulf]

+1 on the reinforcement. I think that you really need it. I'm not sure if the aggregate was the problem. But, for a reverse concrete form you can make the bottom of the form the front. Placing already smooth surfaces toward the bottom will make polishing the face much easier. I broke and used the smooth side of some already broken colored glass panels that I got free from a glass company. I placed (glued) them in the form where wanted. With that you can use what ever type conrcete and aggregate you want for strength.

[david s]

Ah gutted, even left my arch for a couple of days longer just in case. I think the problem is I used my decorative glass as my gravel for the mix, it's really smooth stuff so I don't think it binded. My mix was 1 cement:2sand:3gravel(decorative aggregate). Has anyone had anything like this, or should I have put rebar through it?
Cheers again.

@david s, thanks for the flue advice there, it does rota te so all good to go, just gotta get this arch sorted first

That’s a pity. 3:2:1 not all that strong, especially for a tin casting, add a bit more cement or some thin (5 mm) steel bar and some AR glass fibres.
Also wrap the casting up for a week to damp cure.
you only need the fancy aggregate in the surface you are polishing. Also the aggregate size should not exceed 1/3 of the casting thickness.

[bamforp]

+1 on the reinforcement. I think that you really need it. I'm not sure if the aggregate was the problem. But, for a reverse concrete form you can make the bottom of the form the front. Placing already smooth surfaces toward the bottom will make polishing the face much easier. I broke and used the smooth side of some already broken colored glass panels that I got free from a glass company. I placed (glued) them in the form where wanted. With that you can use what ever type conrcete and aggregate you want for strength.

I'm curious how you created the coloured marbling effect in the concrete. It looks really effective.

[Gulf]

I'm curious how you created the coloured marbling effect in the concrete. It looks really effective.

Thank you very much. Note that the form is upside down. I mixed 3 colors of concrete pressing them in to the form randomly. I placed a small ridge of loose black sand into all borders before adding the next color. (The trial run in the first pic is looks a little thick) I just wanted to create a very slight void between the colors at the very surface. The last pic is after the piece has been removed from the form and cleaned. Most of the loose black sand has been removed from the borders creating thin tapered voids. These voids along with all the other purpose made and natural occurring voids are later filled with a charcoal colored slurry before polishing.

I hope that I am not hijacking the thread but, the middle pic does show ladder wire reinforcement....... and my beautiful helper..... She is almost as tall as me nowadays

[Daveholdn]

So I'm back after a long winter and crazy work time, I inspected the oven over the winter and it's held well but had been kept well covered. I've now added the ceramic blanket and covered in chicken wire.

[Daveholdn]

Also completed the polished arch (adding rebar, a few bits of SS needles and a bit more cement strengthened it) completed the vermiculite layer and rendered the stand.

[Kris S]

Looking good!

I was just wondering what size is your oven opening?

[sergetania]

Looking great! Not that far from pizza time!

[Daveholdn]

Kris S the opening is 43cm which then drops to 40cm with the lip for the door.

[Daveholdn]

sergetania cheers, aye not too far off, just put up the pizza cover so going to start the 7 days of fires as suggested by david s in his previous posts. I've read your posts and the build looks amazing, did you render straight after the curing fires?

[Daveholdn]

Pizza cover done, time for the curing fires starting tomorrow once the flue is extended above the roof