Homebrew?

[CvC]

Hi there,

I would like to use homebrew mortar for my oven, but I have some questions about the ingredients:

It is always said to use "fireclay", but if I translate this, I can?t find anything here that would fit. Can I use normal claypowder, i.e. the same clay that is used by potters or for plastering walls or even in terrariums? Or is "fireclay" a certain type of refractory?

I also am not sure about the "lime", I even found the suggestion to use "quicklime", which would be CaO.

Or do you mean Ca(OH)2 ?

If so, this one is even divided into two different types, the first one only becomes hard in contact with air ( to be exact: the CO2 in it), the other one also contains other components such as CaSiO3 or CaO * Al2O3 and becomes hard even without contact to air and when under water.

So which one of the three limes is the right one?

Thanks for your help,

Christian

[Gulf]

Re: Homebrew?

I wasn't able to find fireclay locally either. I started out with a premix. It was expensive so I began looking for alternatives. I have a wet saw and was able to reclaim the fireclay from the pan. It takes a little work to screen, but it was great to save what would otherwise be a waiste product.
As for as the lime issue, ( I will get blasted for this ) I used masonry mortar. Masonry mortar is about 1 to 1 portland and hydrated lime depending on the particular manufacturer. I just adjusted the formula to fit.

[CvC]

Re: Homebrew?

I wasn't able to find fireclay locally either.

Hi Gulf,

the problem is not only, that I can?t find "fireclay", I don?t even know what to look for!
You cannot simply translate "fireclay", that word doesn?t exist in german.
So I?m not really sure what kind of clay I will have to look for, ordinary pottery clay?

[Cheesesteak]

Re: Homebrew?

Hi Gulf,

the problem is not only, that I can?t find "fireclay", I don?t even know what to look for!
You cannot simply translate "fireclay", that word doesn?t exist in german.
So I?m not really sure what kind of clay I will have to look for, ordinary pottery clay?

Fireclay, at least in the States, is also called "Mortar Clay." Maybe that will help . . .

[Mingy]

Re: Homebrew?

I spent a lot of time tracking down materials. I don't know how to translate fireclay (google says Schamotte), but I would suggest you keep looking for proper 'refractory mortar' (google says feuerfestem M?rtel). I strongly suspect where you'd find one, you'd find the other. Refractory mortar is very expensive (10x the cost of regular mortar here), however, the mortar and bricks are the two most important components of the oven from a reliability perspective. Given all the hard work involved, I woudl strongly suggest you use those materials.

I believe refractory mortar uses an aluminum compound.

I did a quick search on google for refractory mortar Germany and found this company
Germany

SEPP ZEUG GMBH & CO. KG
Sepp Zeug, Jr.
011.49.7031.2730.26
011.49.7031.2778.74 (fax)
sepp_zeug@t-online.de

I'm sure you could find others

[CvC]

Re: Homebrew?

Shortcut version:

Hi there,

I would like to use homebrew mortar for my oven, but I have some questions about the ingredients:

Can I use normal claypowder?

Which lime is the right one?

Thanks for your help,

Christian

[Dmendo]

Re: Homebrew?

Hi cvc.
Regarding the clay, you have to look for refractory clay, the mix includes clay and refractory schamotte. A quick google in german lead me to "Schamottem?rtel", available here:
Feuerfeste Chemotechnik, Fasertechnik, Dichtungsschn?re, Reinigungsb?rsten
Although you can for shure find out better prices in refractory providers for ceramic kilns or furnaces. All the ways I don't have a clear idea of which product is the correct there. All the ways, fireclay or refractory clay is used as no cement mortar in kacheloffen bulding in Germany.
Regarding the lime, after deep search in this forum I reached the conclussion that the correct lime is the calcium hidroxide:
Ca(OH)2

Regards

[Amac]

Re: Homebrew?

Regarding the lime, after deep search in this forum I reached the conclussion that the correct lime is the calcium hidroxide:Ca(OH)2

I used "hydrated lime" . But now I am confused, it is called calcium dihydroxide whose chemical formula is CaH2O2. H2O2 sounds to me suspiciously like (OH)2. 2 hydrogen and 2 Oxygen right?
In this link it only shows calcium dihydroxide. I suspect it is the same but..any chemists in the forum?

calcium dihydroxide, CAS Number: 7719-01-9

From wikipedia:
Lime (material) - Wikipedia, the free encyclopedia

Limestone is extracted from quarries or mines.
Part of the extracted stone, selected according to its chemical composition and granulometry, is calcinated at about 1000?C in different types of kiln, fired by such fuels as natural gas, coal, fuel oil, lignite, etc.

Quicklime is produced according to the reaction: CaCO3 + heat → CaO + CO2. Lime is used extensively for waste water treatment with ferrous sulphate.

Quicklime can be hydrated, i.e., combined with water.

Hydrated lime, known as slaked lime, is produced according to the reaction: CaO + H2O → Ca(OH)2

The most important thing is use hydrated lime and NOT quicklime

As for the clay - I would say pottery clay would be OK but I imagine it would be far too good a quality and consistency (and correspondingly expensive) to be used as a mortar additive. The brick manufacturers or fireplace installers should help you there.

[Amac]

Re: Homebrew?

Christian

(to be exact: the CO2 in it)

I guess that's a typo and you mean CaO2 - since although you will expend a lot of CO2 in the oven, breathing alone won't be enough
Mistakes in chemical formulas can lead to unexpected results. It reminds me of the old school rhyme:

Johnny was a chemist
But Johnny is no more
For what he thought was H2O
Was H2SO4

Good luck with your oven
Aidan

[GianniFocaccia]

Re: Homebrew?

But, over weeks or months or even years, the Ca(OH)2 + CO2 from the atmosphere, turns into CaCO3. i.e. given enough time the lime in your mortar turns to limestone again.
A far as I can figure it, the homebrew mortar is relying on the Portland cement surviving long enough to give the lime time to cure into the CaCO3

Thanks for this explanation, wotavidone. The conversion of Ca(OH)2 into CaCO3 over time is really interesting and explains why lime takes over when portland begins to fail from repeated thermal cycles. I wonder if there is a benefit to substitute (a certain percentage of) lime for portland in the homebrew mix and how long it would take to gain strength.
John

[Amac]

Re: Homebrew?

Wotavidone

But, over weeks or months or even years, the Ca(OH)2 + CO2 from the atmosphere, turns into CaCO3. i.e. given enough time the lime in your mortar turns to limestone again.

- the things you learn on this forum
And I thought all that huffing and puffing had no effect on the mortar - so the bigger the number at your pizza party the tougher your oven becomes - just get them all to breathe out towards the dome

By the way, I'm an assayer. Sort of a practical and applied chemistry sorta guy, we don't like to call ourselves chemists.

How about alchemist
Aidan

[DTHERR]

Re: Homebrew?

Has anyone else tried the "calcium aluminoslicate" home brew ? I use it everyday in my countertops as a additive so have access to it so cost is negligible .. Does it make a better refractory mortar then the portland brew?

[CvC]

Re: Homebrew?

Christian


I guess that's a typo and you mean CaO2 - since although you will expend a lot of CO2 in the oven, breathing alone won't be enough
Mistakes in chemical formulas can lead to unexpected results.
Good luck with your oven
Aidan

No,

that formula is correct, besides, air does contain some CO2, but no CaO2.
I understand the chemical reactions quite well, my problem is my lack of practical experience in building ovens.

[Tscarborough]

Re: Homebrew?

Actually it does "go off", but it does not do so like cement, i.e. turn into a rock.

[CvC]

Re: Homebrew?

Chaps one note of caution about relying on the Hydrated lime to combine with the CO2 in the air to make CaCO3. I reckon its going to take a very long time, especially if its dry. Lets face it, an open bag of lime doesn't "go off" in your garage. I can't really explain it in any sort of logical terms, but I reckon it'd need to be damp to help the reaction along.

In fact, it is known, that even walls built of lime cement in the middle ages are not already completely turned into CaCO3, because of the thickness of those walls.

The reaction is of course controlled by diffusion, which can take a very long time, but in fact, the reaction doesn?t stop as long as there is any Ca(OH)2 left.