D105 Pre-Cut brick kit build in Tassie

[PizzaCharlie]

Love the snail look of the oven.
I'm up to the curing stage as well with my build. Just reading up on the best way to start it off.

This website suggests the first firing to be done with newspapers. But how many newspapers? And for how long? Newspaper burn for like 2 mins if anything. Other sites I've seen a few pieces of wood and what looks like a strong fire for the first firing. Confusion!

How are you going to go about your first fire steady?

[Steady]

There was a break in the weather over the weekend and I managed to finish the insulating render (on 1st Aug 15) Now there is a dusting of snow this morning.

I am ready to start my curing fires - I just need to find some time and good weather.

[Steady]

I had hoped to finish my insulating render this weekend but the weather is against me. I went looking for some perlite/vermiculite to discover it is different than the "litefill" that came with the kit. I think I am about 30 litres short but what I can find in bunnys and the local nurserys has a far bigger particle size. The litefill was about the size of half a grain of rice.

What size have others here used?

[Steady]

looks really nice how have you found the kit to put together ??

I am looking forward to putting mine together,

Thanks philby303 !

I have been very happy with my Melbourne Fire Brick Kit. It has gone together really well, and aside from the insulating render coat where I have made a layer thicker than I should so have run out - I have had ample materials. The video and written instructions are comprehensive but simple to follow.

The kit does some things differently than a full blown do it yourself Pompeii brick oven, and unless I deviated in a major way did not allow me to follow some of the latest learnings/thinking developed by wise WFO'ers - like installing a thermal break outside the inner arch, but this is something that I can live without on my first build.

I'm very happy with the kit and proud of what I have built - friends and colleges are getting sick of me showing the photos....

[philby303]

looks really nice how have you found the kit to put together ??

I am looking forward to putting mine together,

[Steady]

I got most of the final insulating layer on my oven yesterday but ran out of "Litefill" late Sunday afternoon and could not get more.

I will not be able to finish it until next weekend, weather permitting - there is nothing I can do about it now but I am guessing the join is likely to be a weak point that may develop a crack?

[Steady]

I managed to get another layer of insulating render on today, I'm hoping to get another on tomorrow - it will probably finish off the 300 litres of vermiculite that came with my kit.

[Steady]

Re: D105 Pre-Cut brick kit build in Tassie

No, I can't see that it would make any difference.

Thanks David

[david s]

Re: D105 Pre-Cut brick kit build in Tassie

I have a question in regards to vent location

Would a low vent as opposed to one in the TDC make much difference to how much moisture can get out?
.

No, I can't see that it would make any difference.

[david s]

Re: D105 Pre-Cut brick kit build in Tassie

Yes, I'd agree with all of that. You've obviously been doing some thinking. The beauty of building firing and cooking in your own oven deepens the understanding of everything that's going on. Forge on!

[Steady]

Re: D105 Pre-Cut brick kit build in Tassie

Thanks for the info david s. I will leave the cement render off until the vermiculite render has dried out using the plastic sheet method to test. I suspect the K value of my V-render will be lower than many others on here due to the addition of sand. Like many others when I finish my oven I expect I will have a list as long as my arm of things I would do differently next time. I can easily drop the sand out of the mix - looking at the kit instructions I downloaded in Jan 2015, the render was only 1 part cement and 5 parts vermiculite - this has since been revised. The instructions currently on the MFBC site for download has the sand and lime added to the mix.

I have a question in regards to vent location options,

Pressure caused by steam, from moisture entering via the hearth or similar (in the future after everything has been dried out) that is trapped by the eventual external waterproof membrane would be equal in the air void / blanket space - so as a pressure reliever the vent could go anywhere. A PVC capped vent closer to the bottom where it can be reached without a ladder would be more practical.

Would a low vent as opposed to one in the TDC make much difference to how much moisture can get out?

This is my rudimentary understanding thus far for after the oven is dry and cured and then maybe gets wet/damp during winter next year - if I have it wrong please correct me;

The moisture that re-enters the vermiculite render layer, wicking through from rain on the hearth or directly from cracks in the external waterproof membrane etc is going to be driven away from the heat of the next fire, towards the waterproof membrane and then be stopped by it - I have been assuming this would result in one the following happening;
a) the moisture will blister an acrylic coating or similar and eventually escape
b) the heat would build and eventually turn the moisture to steam with it expanding and making its way back into the blanket void space eventually exiting via a crack or installed vent.

The moisture will be evident by the external surface of the dome getting hot as the insulation is inefficient when wet/damp but as it re-dries the outside will cool back down. The moisture in the V-render turning to steam can/will crack it as it expands so keeping it bone dry in the first place is the ultimate goal - venting is the mitigation.

[david s]

Re: D105 Pre-Cut brick kit build in Tassie

And another on some tests I made with drying a vermicrete slab. The same applies for vermicrete over the dome.

[david s]

Re: D105 Pre-Cut brick kit build in Tassie

Here's some info on vermicrete re strength etc.

http://www.schundler.com/vermcon.htm

[david s]

Re: D105 Pre-Cut brick kit build in Tassie

It depends on what you want the vermicrete layer to do. If only needed for insulation and just firm enough to render against 10:1 is ok. If you want some strength a richer brew like 5:1 will increase its strength a lot, but reduce its permeability a lot, sand even more so. Making the vermicrete rich also drastically reduces its insulation value. I don't know how thick your vermicrete layer is and I don't want to interfere with whatever Ben's build instructions say, but the moisture contained in the layer needs to be removed at some time. From my experience it's better removed before doing the final render.

[Steady]

Re: D105 Pre-Cut brick kit build in Tassie

When the vermicrete has dried I like to do the curing fires to be sure there is no moisture in the insulation layer, before doing the cement render outer shell. You may want to consider putting in a vent so your insulation layer can communicate with the atmosphere to relieve steam pressure build up.

and an old post from 19-05-2013 #72 new build in werribee

Looks good to me Steve. I think that the problem of the outer shell cracking is caused by large amounts of steam creating pressure. A vent can go some of the way to relieving this, but steam will still have trouble finding its way through the vermicrete to the vent. I've found that once you get the oven dry any subsequent rain and moisture take up by the insulation layer is dealt with quite adequately by the vent. A hand held to the outside of the oven can be a great indicator of the dryness of the insulation layer. If it is moist it makes the outside of the oven hot, rather than just cosy warm (in my ovens at least) depending how you have done your insulation and how thick it is, this may vary.

Dave

I was having trouble understanding how a vent just through the cement render onto the outside surface of the cured vermiculite render would do anything but after some more research I found your post (david s) in Greenman's build thread that I can understand.

I have followed Ben Guilford's kit instructions for the vermiculite render (well almost) and it is made up with;

1 part Portland cement,
1 part fine washed sand
1 part lime
5 parts vermiculite - except I went 6 parts.

Is this similar to the mix others have used on here? if not will it make a difference to the vent advice?

Some of the photos of vermiculite render I have seen on here look way more porous / have a really rough surface compared to mine - maybe its just the particle size of the vermiculite - mine being very small