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Things seemed to be going alright until I tried speeding up the drying in the oven.

Apparently when noodles burn they don't just turn to ash but swell up or something:


The underside seems ok though:


The noodles did not burn away, but I'm guessing pyrolyzed and swelled turning to hard charcoal like material and not really loosing much weight and probably difficult, if not impossible to remove.


As for the paper clay made with actual paper fiber, I think it would have been fine, if not for the damage from the noodles swelling

Another drawback of the noodles is they do burn and smoke quite a lot.

I'm thinking this method might work with something else like some kind of paper tubes that would shrink and burn out more easily.

Not nearly the disastrous results using stir sticks and ordinary clay without the paper fibers. Other than what could be considered cosmetic damage on one side, the displacer is potentially useable, though it still has not been fired in a kiln, only heated to maybe 400°F in the oven. But basically nice and flat and seemingly strong. I was not even able to break loose the apparently loose damaged strips, in spite of appearances they were quite well adhered to the larger part of the displacer.

This is an interesting development.

A few days ago I broke down and ordered the largest microwave kiln available from Amazon. It just arrived this afternoon a few minutes ago.

What is interesting is the material it is made out of is not at all what I was expecting (something similar to the DIY versions, like plaster of Paris or some such thing)

These kilns seem to be made out of some very lightweight foamed-glass or pumice or Perlite -like material. It has a glass-like feel and sound when handled.

Comparing it with the hemp fiber porcelain displacer, I estimate the size of the kiln base to be at least 20X bigger than the displacer but not 20X heavier. Possibly more like 25X bigger.


The displacer is 31 grams, the kiln base is 214.

So, a displacer the same size made of this kiln material, whatever it is, would probably weigh under 10 grams. or less than 1/3 the weight of the fiber porcelain, but still 2 or 3 times heavier than the original foam displacer.

I'm tempted to just slice a section out of this kiln and use it as a displacer.

This is an interesting video.

More and more I've been leaning towards something like based, the more I find out about it.


https://youtu.be/DyjcRNJBk-s


The patent for a mineral foam mentioned previously that I'm anxious to try:

viewtopic.php?f=1&t=5415&start=135#p19120


Is also lime and water glass based with the addition of the silicon powder to cause it to foam.

This could be useful. The basic observation that Portland cement just does not hold together as a refractory but crumbles to powder has been my experience also, however, there may be a solution.

I did try subjecting some of the aircrete that had more time to cure to the torch, heating it to red hot.

It seemed unaffected. The aircrete took the heat great without cracking, that is, until I tested it for strength and it just crumbled.

In this video the aircrete is treated with waterglass. Apparently, this simple treatment with a dilute waterglass allows the aircrete to hold together quite well under refractory type heat.


https://youtu.be/NcVlb-z6Y94

Follow up video:

https://youtu.be/DPOCfPhijwM

Feeling ambitious, and taking some clues from the various videos, I decided to try the Drexel again, but this time I'm seeing how it works with clay.

Well, not just clay. There is kaolin clay and bentonite clay, some Perlite and also quite a bit of crushed dolomitic lime. A sprinkle of sodium hydroxide (drain cleaner) and a cap full of undiluted sodium silicate. And also some Portland cement.

This time I just used a few drops of Drexel and foamed it up separately and mixed up the other ingredients with enough water to make a normal cement-like consistency before folding in the foam until the mixture doubled in size. There was a lot of left over foam.

This time the mixture did not suddenly shrink down and it also looks much more foamy.

The foam bubbles on the surface are gradually popping but the substance is retaining its shape . That is, when a bubble pops it leaves a hole which does not fill in but leaves a pomace like surface.

It's been out drying on the table overnight and there really doesn't seem to be much change, other than it has lost the wet looking glossy surface.

I poured out two samples. The larger one was a little more foamy. The smaller sample was the scrapings from the bottom of the bowl that still had some heavier chunks of perlite. I just put that in the oven.


Sorry, that looks just like the previous pictures. I was able to move it easily without it visibly cracking and falling apart. Zooming in on the photo though, I can see some hairline cracks or stress lines developing, or due to moving it on a floppy old paper grocery bag.

Anyway, one thing possibly worth mentioning. I did throw in a lot of Perlite. By volume, probably at least twice as much as any of the other dry ingredients, but there was hardly any chunks of Perlite in the bottom of the bowl and none are really visible in the foam, which is a nice smooth consistency rather than having a lot of lumps from the angular, chunky bits of Perlite.

So, what happened to all the Perlite I dumped into the mix?

The mixture itself was not mechanically blended, only the Drexel and water was subject to high speed mechanical blending, then the foam was gently folded into the other pre-moistened dry ingredients, with the added water glass and sodium hydroxide.

Is it possible the drain cleaner dissolved most of the Perlite? It is what is used to dissolve sand to make water glass, so it seems conceivable that due to the porous nature of the Perlite it very readily dissolved in the presence of the sodium hydroxide, though I used very little of that. Maybe a teaspoon. There was about three cups of Perlite in the mix. Less than a cup each of the other dry ingredients, powdered kaolin, powdered bentonite and Portland cement in nearly equal proportions.

Anyway, I'm leaving the larger sample out of the oven. I might even wet it to extend the drying/curing time, especially if that smaller sample now being dried starts to crumble.

Well, no sooner did I say it...

I just took a peak in the oven, on the lowest possible "warm" setting and the stuff was starting to separate from the paper, in a way that did not look good.

A slight touch and it crumbled into dust.


I think I will give the larger sample a spray of some water.

I decided to try the waterglass treatment on the small dry sample (what's left of it) and 1/2 of the large sample.

The right side is sprayed with a very dute water glass solution, the left with plain water.

The waterglass had the effect of causing all the surface bubbles to pop producing more of an open pore structure. The plain water did not.

The water glass solution also seems to have effected the paper bag in some way, causing it to turn dark. It just looks wet. But the plain water did not penetrate the paper as much. I'm surprised there is a y difference as the waterglass was very dilute. Probably only about 5%

I don't particularly like the idea of trying to compensate for the material failings of the samples by soaking them with water glass. Actually, I would prefer not to be using the stuff at all if it could be avoided, especially putting it in a spray bottle, baking it in an oven or kiln etc. and inevitably breathing in some of the mist or fumes.


Rumor is, Portland cement is death to any kind of refractory, as mentioned several times in the above videos. though he wanted it to work. Cement likes to stay wet, indefinitely if possible.

Anyway, I may try using the Drexel with a clay mixture without the Portland cement. Possibly without anything else Maybe some hemp fiber. That was my original plan. The hemp fiber paper clay, for the most part turned out good, just a little heavier than I would like, so I wanted to try some Drexel foam added to the paper clay to lighten it up some.

Possibly just using more fiber, or adding some Perlite would work but the foam would be great, if it could work with the porcelain and not fall apart.

Not much to complain about with the fiber clay

https://youtu.be/sbrH5rqRuVs

I have also been experimenting with Hempcrete made using just Lime (calcium hydroxide / pickling lime)


Not completely dry yet, but so far the Hempcrete seems to be holding up under forced drying in the oven much better than my foamed cement/clay concoction.


https://youtu.be/R7XjQ7iveLk


BTW, it looks like the Perlite is still in there.

Also, the soaking with dilute water glass seems to have done nothing for it

The lime hempcrete is turning out to be very light weight after drying in the oven for a while.


This fairly large and thick chunk is .measuring just 10 grams, compared with 31 grams for about the same size fiber clay. The hemp Crete is, however, beginning to get more and more powdery and crumbly the longer it's in the oven


I've also seen on videos, regarding the flame resistance of hempcrete As an insulating material it will not burn, or will not sustain a flame or catch fire, but it will crumble to dust in a fire eventually, so is probably not suitable as a high temperature displacer material in the long run.

I must have spent the last five hours trying to cut rings out of some jars for the displacer chamber but it did not go well:


Just a lot of broken glass.

The idea is to replace the melted plastic with something that could take higher temperatures,


I found some pickle jars about the right size, but can't get them to cut cleanly without cracking.

I finally ran out of bottles so am resorting to using the fiber clay, which so far has gone pretty well.

Just rolled out some clay, cut a strip, wrapped it around a piece of PVC pipe that was the same OD as the displacer chambers ID, joined the ends and trimmed it down.

Now I can do something else while that's drying.

I also put the displacer on.

Hopefully the high temperature JB Weld will hold it on.

It may be 10X heavier than the styrofoam but I am counting on the higher temperature made possible more than compensating for the added weight.

Besides, won't the energy used to lift the displacer be returned when it comes back down?

Haven't given up yet.

This is just crushed limestone made into a paste with Drexel foam blended into it (with a twist).


This time I added the Drexel directly to a fairly high water glass solution. I think maybe about 30% or 40% waterglass straight out of the bottle.

It only took a few drops of Drexel to make about 1/4 cup of water glass solution into a foam.

This is an attempt to produce a lightweight version of the "refractory glue" in the above video, which was just sodium silicate (water glass) and "garden lime".

What I have though, is Dolomitic lime, which may not be exactly the same as his "garden lime".