DIY refractory from soil paper and sodium silicate
This post describes dirt cheap DIY refractories made with paper, soil and sodium silicate. They can form tough refractory materials from loamy soils with very little clay content. The paper makes molding easy and aids rapid even drying and reduced cracking.
In a previous post, I described a wide variety of DIY refractories made with sodium silicate. Many had lightweight refractory fillers to make the fired aggregate very light. These fillers made the mix more crumbly and difficult to mix, handle and form to the required shape.
Since writing that post, I have learned a little about the wonders of ceramics made of paper and clay. This started after receiving a message from Rudy who read my silicate refractory post and he supplied information on paper clay.
It simply uses toilet-tissue paper-mash as a filler and binder to make the clay very easy to handle by a mug like me. The paper burns away during firing and leaves a lightweight ceramic. I have reported on this in another post DIY refractory paper clay.
Covid19 was not all bad
I had plenty of toilet paper that was hoarded for the Coronavirus Pandemic. I was waiting to get some quality clay to make my first paper clay test piece. Being a little impatient, I set about experimentally using some ‘crab-hole soil with paper. This soil had great success as a ‘dirt-cheap’ silicate refractory as described in the top post.
The finely sifted crab-hole soil mixed nicely with the paper and was very easy to handle, shape and dry in preparation for firing. Alas, after firing, The test piece just fell apart into dust. I think this happened because the crab-hole soil felt like clay but had little clay in it.
“Ahhhh…well nothing lost, but it did give me the idea of trying the combination of crab-hole soil+paper+sodium silicate to see if it would make a stable refractory.” It may be easier to mold, quicker to dry with less cracking and much less dense after firing.
While investigating sodium silicate properties I learned that some very fine refractory minerals, often an industrial cutting waste, help to prevent intumescence (puffing or expanding) during silicate composite firing. I thought the finely ground crab hole soil may just have this property.
Consequently, I suspected that my crafty crab-hole soil with paper and sodium silicate would be worth a try.
Paper, crab-hole soil and sodium silicate refractory
My starting point for this test was a big slab of dried out crab-hole soil and toilet paper mash. It was leftover from the failed experiment when I did not use sodium silicate. I just added about 5% by volume of sodium silicate concentrate and the same amount of water and mushed all together to make a putty-like texture. I further mixed by rolling and folding repeatedly between sheets of plastic cut from a stiff food bag. The method is described in DIY refractory mixing.
The mixture was easy to cut, handle and could be joined easily and smoothed and manipulated with a spatula. The paper fibres seemed to help the moulded parts to join easily and dry quickly without cracking.
The crucible and disk have portions that are a little shiny and I think this indicates that during firing the sodium in the mix is fluxing the soil and less sodium silicate in the mix may prevent this. On the other hand, if a gloss was desired, the surface could be treated with extra silicate and it could be fired for a gloss in a second firing.
I think the relative success of the ‘paper’ refractory with silicate, when compared with none in it, demonstrates that silicate must be the bonding agent in my crab hole refractories and my soil must have very little clay in it. The crab-holes from a park that was in a different geological location (about 10k away from my farm) also needed sodium silicate added to form a strong refractory.
More paper silicate mixes to come……….
Tim
I’m not super informed about firing and clay bodies BUT, as far as I understand red clays (aka earthwares) are the most abundant type of clays, easiest to find, and fire at lower temperatures than denser, lighter colored clays like stonewares and porcelain. The red comes from iron oxide.
Thanks Ole, That probably explains my better success with my red paperclay. Tim
Another idea. I have read that clay responds very well to being aged in the open. In fact I have heard that you make a pool of clay and pee in it. The pee makes bacteria, yeast, etc. multiply in the clay. This supposedly makes the clay far better for firing. Supposedly. Could it be that this is some of the same sort of thing that is going on with adding fine paper? Could the bacteria and yeast make tiny spaces that keep it from cracking when dried or fired?? I don’t know but thought I would relay that odd info I read. Maybe it will come in handy to someone.
An idea if you made a big batch of yeast with sugar it would be faster, and more sanitary, than peeing into the clay.
Hi Sam, This post is about making refractory from ‘essentially clay free soil’ and the sodium silicate is used as the refractory binding agent. No clay is involved. Regarding aging of clay……well, it is already an aged material. As I understand it, it comes from certain aged and weathered rock that turns into clay. Once mixed with paper (and left damp), the paper clay mix does ferment (without addition of: pee, added yeasts or other nutrients and it goes ‘stinky’. After all, paper is made of cellulose which is a complex sugar. However it seems to have no good or bad effect on the end refractory. So I don’t think such a source of ‘tiny holes’ would be contribute to making a better refractory.
Lastly, regarding clay free soil refractories, I have noticed that termite nest material (made from my clay free soil) forms a natural refractory in the honeycomb shape of their nest chambers after high temperature firing. Presumably their spit, pee or other excretions are providing the necessary refractory binding agent. I have also found that some other animal scats behave similarly and become solid and ultra lightweight refractories when fired, so who knows what magical chemicals life may be adding in here.
Tim
In regards to paperclay strength, someone recently published a paper (I’m not in the mood to find the link but it’s out there) saying that the water used to soak newspaper for making paper pulp should be used to hydrate the clay powder, because it will add a lot of strength. I assume that’s because of starch in the water. In natural building world, as well as in bell casting, materials like cob or sand mixtures are sometimes fermented to add strength (or in the case of bells, to affect the bell sound quality in a mysterious way). The Recho Rocket project (low-cost rocket stoves) uses a refractory made from local clayey soil, organic material (donkey dung, can replace with paper pulp), as well as a weak sugar syrup and lye water. I assume the sugar is initiating fermentation on some level, as the project is in Haiti and the material would start fermenting quickly in the heat.
As far as the scats, they’re very useful as burnout material mixed into clay/sand/alumina/whatever ground rock you’re using, but alone?
Regardless, fermentation does have a place in building and insulating technology. Someone with more understanding of lignan chains etc etc should chime in.
Relatedly, this guy (https://yewtu.be/watch?v=I6auqbKBjPE) has some interesting experiments with making fermented sawdust/coffee ground briquettes, claiming they burn hotter and significantly longer than unfermented briquettes. An engineer friend theorized that he’s basically making charcoal- breaking down or releasing volatiles via fermentation, then removing water through slow drying.
I also wanted to add that Graham Hay has some great tips on making paper clay here: https://yewtu.be/watch?v=PGvI4eamP1s
Hi Ole, Thanks for your detailed comments.
Regarding the inclusion of the paper-soaking liquid in the paper clay mix, I have been doing that without knowing its importance for the fired clay body strength. By the way the video in your last suggested link (GrahamHayArt) mentions this issue and quotes a published thesis on the subject (Paper-Composite Porcelain- Jeoung Ah Kim). I doubt that there would be much sugar in that liquid as paper is complex carbohydrate that takes something like a cows stomach to break it down into smaller sugars. So I expect that it will be some other chemical/substance. Reading the Thesis should sort that out.
If sugar was the trick, we could easily use supermarket sugar to work such magic, but there will be many organisms just waiting to eat or ferment it.
The fired scats are interesting. Here is the link to my post about it
Understandably, the post has not fared well with Mr Google and to be honest, I am not certain that they were fox poohs. I just found them where a fox had visited. Nevertheless, I found that after accidental firing at 1,200+C. You see, I popped them into the furnace with other backyard scraps to feed the inferno. After all that they turned up in the ashes quite light and strong and with the intricate ‘Oooooh-Arhhhh’ details that they were ‘shat with’, less the hair fibers of course.
Regarding fermentation of fuels. It may improving combustion duration and or combustion temperature of such briquettes? However, from a total combustible energy stand point, all such fermentation uses energy from the fuel and degrades the amount of energy that is left for combustion. I have an agricultural research background and fermented silage lost significant amounts of its combustible energy during the fermentation/preservation process. We used pantyhose legs that were stuffed with the harvested pasture and they were recovered when the silage was fed out. ALL fermentation has an energy cost.
Going back to you last mentioned video (GrahamHayArt), the testing of the fineness of the paper pulp (using the wine glass) seems to be a critical part of the process and I think I may do better with my paperclay if I pay more attention to the mixing to prevent large particles of paper in the mix. I think animal manures (donkey pooh) would also contribute large organic particles to the mix. Although, this seems to be quite effective for primitive baldosa tiles. Who Knows?
Lastly, I have tinkered with my home made stone ground wholemeal flour as an organic filler for refractories but don’t think I have posted on it.
Thanks again for your comments and ideas, Tim
Ah yes, that’s the thesis!
Re: energy lost in fermentation. I THINK, in the case of fermenting sawdust, this is similar to the energy lost in producing charcoal. You lose energy, but get a hotter burning fuel as a result.
Re: Fineness of fibers in paper pulp for paper clay. I also make ceramic art, and I’m fairly certain the importance of finely blending the paper pulp is so that fibers don’t make an visible impact on artwork, and to make paperclay easier to work with as a sculpting material. I think it’s likely better, or at least not important, NOT to blend the pulp as finely for refractories. Those larger visible flecks of paper in the graham hay video may lend more strength, or not compromise it, when burned out.
Hi Ole, Yes what you are suggesting makes sense with regard to ‘art’ and ‘functional refractories’. The manure and straw Baldosa tiles have worked well for a long time without only fine organic particles. Tim
Hi again Ole, A quick question of you. Do you find that red clay fires more easily and at lower temperatures than white clay? I have had more success with red paperclay than the white paperclay? Tim
hi! thank you so much for figuring this out, i have a quick clarifying question: am I correct that you’re mixing 1:1 parts dry soil and wrung-out toilet paper mash by weight, and adding 5% of the total soil/paper mix by volume of sodium silicate?
Hi again Anon, You are correct. Depending on your choice of loam soil it may require a different ratio of paper mash to soil, but by making some little thin test disks out of your magic mix, you will get your own answer. Thin disks such as shown in the post are quick and easy to make, without any mold. They can be dried/cured quickly and fired all in one day and you can have several mixes tested to see what works for you. Tim
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