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skyofcolorado wrote: ↑Fri Apr 28, 2023 8:16 pm What's the final grams per cc of that substance after firing? Does it take a direct torch flame okay?

The fiber clay? Don't know yet. It is just out of the oven, where I only warmed it to help dry it out.

It came out of the oven slightly misshapen but was easy to sand down nice and flat


I will, of course, post the results once it is fired in the kiln, assuming that works, and the displacer survives.

At this point, I found that the material I more or less randomly mixed together on a whim to coat the silicon carbide is looking like a potentially very promising material for use as a displacer.

Often I have found that refractory cement of various sorts tends to crack and eventually crumble with repeated heating and cooling, but not this stuff (so far)

There was a left over glob of the 50/50 Plaster of Paris and Perlite (with a little water glass) mix that dried out on the bench over the past few days. It seemed quite lightweight and surprisingly strong, so I went ahead and subjected it to my usual torture test:


https://youtu.be/0Oc1qBVWkvs


I've made up various plaster and perlite mixtures before, but this time I really wanted to avoid any cracking or shrinking for the microwave kiln.

I had some previous experience with making concrete block. For that, the concrete has to be mixed up dry as possible, really just enough water to dampen the mixture without it being at all liquid or runny, that way it can be packed into a form and the form removed immediately for use in making the next block. These dry mix concrete blocks do not shrink much at all, or crack when drying, as, for the most part they are practically already dry to begin with.

So I thought I'd mix up the plaster and Perlite in the same way like an almost dry concrete block mix.

The wet plaster and Perlite mixture was about the same consistency and appearance as cottage cheese. If there is too much water the perlite will tend to float to the surface.

The only real problem with such a dry mixture is that it sets up very rapidly, right in the bucket if you don't keep stirring or don't use it fast enough. It sets up almost immediately.

The little bit of sodium silicate seems to make it set even more rapidly.

With the first batch I diluted the water glass in a cup of water and added that to the dry mixture first, then added enough plain water to bring the mixture to the right "cottage cheese" consistency while stirring.

When I made the second batch, I poured the cup of water with the tablespoon of sodium silicate in last and as soon as I poured in the cup of water with the waterglass into the already wet mixture it set up in the bucket and I had to add a little more plain water and give it a good stirring to loosen it up again.

This seemed very strange, as I poured in this liquid water + water glass and instead of getting more soupy, the mix set right up so rapidly it was unbelievable. The waterglass seemed to act as a catalyst similar to a very rapid setting two part epoxy.

Now I'm thinking of trying the same mixture with some foam mixed in to make it even lighter

Here is a video that shows how rapidly concrete block can be manufactured using a very dry mix.

My plaster/perlite + waterglass mix was not quite so dry but pretty close.



https://youtu.be/x_SPFyxjzSU


Years ago there was a local guy welding together small hand operated block making machines like that and selling them for about $500.

At the time I was making these honeycomb blocks for growing seedling trees in

https://www.google.com/search?q=peoples ... IgAQ%3D%3D

I had been making them with a form I had made from PVC pipe

Those blocks BTW have proven to be very durable. I made them as an experiment and they've been kicking around in the yard outside, through all kinds of weather, freezing and thawing in winter and hot summer sun for,... too long ago to remember, but I'm guessing about twenty years...

Anyway, still as strong and solid as the day they were made:



I just stepped outside now and took that photo.

Back then I was trying to grow certain deep rooted trees, like Pecan, from seed. They would be impossible to dig and transplant without damaging the long taproot. Grown in these honeycomb cement block cells, they could be allowed to grow naturally, as if in the ground, right through the winter for a few years, and then could be transplanted easily without damaging the vital tap root or causing a lot of transplant shock just by disassembling the concrete honeycomb.

I should really get back to that tree nursery project some day soon.

Those blocks are very heavy though. So I eventually got interested in foamed cement for that reason. To make those plant/tree growing blocks easier to handle.

The rapidset CSA mix from home Depot is my go-to for so many little structural objects (like my current stirling engine - 90% cement.) Relatively inexpensive vs. resins, super fast and hard, plays well with high-detail silicone molds, takes fibers for extra durability, easy to color, stain and seal.

Also easy to foam it if weight is an issue, but a perlite or styrofoam blend is less fussy.

skyofcolorado wrote: ↑Sat Apr 29, 2023 8:55 am The rapidset CSA mix from home Depot is my go-to for so many little structural objects (like my current stirling engine - 90% cement.) Relatively inexpensive vs. resins, super fast and hard, plays well with high-detail silicone molds, takes fibers for extra durability, easy to color, stain and seal.

Also easy to foam it if weight is an issue, but a perlite or styrofoam blend is less fussy.

I'm interested in your 90% cement Stirling engine.

A problem with rapid set type cement, I think, is long term durability under extreme conditions. It may just be me, I don't know. How I've been mixing it? But none have survived my "torture test" of rapid heating and cooling, they all have cracked and/or crumbled after a few cycles. Foaming to make it lighter and/or thinner just seems to make the problem worse but I'm certainly open to suggestions.

I just came across this video which, other than the long introduction about football, which I found annoying (I don't have a lot of patience sometimes, please get to the point I kept muttering) had a few tips for using cement sealer (which is, apparently just sodium silicate) and how to cure it with gas produced from baking soda and vinegar was quite interesting:


https://youtu.be/ZoIL3j-eblc


I think getting the mixture to set rapidly is probably a good way to avoid shrinkage. I may try the baking soda and vinegar trick next time.

I tried the baking soda and vinegar thing, but this mix sets so fast it doesn't seem to make a difference.

Actually, if anything the sample treated by that method from the same batch seemed to have less strength or took longer to set and dry as hard as the untreated half, perhaps due to being covered in a more humid environment.

It seems the kiln is working ok.

Seeing the general heat resistance and durability of silicon carbide fused together with waterglass to create a heating element for the microwave kiln, I had another idea.

Pieces of the silicon carbide shell did not actually seem all that heavy. Maybe that could serve as a high temperature displacer.

I wanted to see if possibly it could be made lighter, so I sifted some Perlite, mixed that with some silicon carbide then made a paste with that with some water, some paper pulp and water glass.

I kept adding dry paper pulp and mixing it in until I got a rather thick, clay like paste, shaped it and rolled it out to the right thickness for an LTD displacer, dried it in the kitchen oven and then popped it in the kiln.


Looks good so far in there, but won't know what the results will be until it cools down and I can get it out of there.

The results of that little experiment turned out a little odd.

After the kiln cooled down enough to get the displacer out, one side seemed to be covered with a white powder which I brushed off, but it kept brushing off, further and further into the disk. Eventually the only thing left was a kind of dish.


I did not pay close enough attention which side brushed off, but I think it was the bottom side, which would have been shielded from direct radiant heat from the domed kiln above.

It seems the Perlite and silicon carbide on the upper layer and sides exposed to the most heat fused together, however, it does not seem like silicon carbide granuals any more. It is more like the consistency of burnt toast or charcoal.

At first I thought the silicon carbide had somehow settled to the bottom and the Perlite floated to the top ?

I'm pretty sure though that the powdery side was on the bottom.

Anyway, the remaining disk is pretty hard and fairly light weight. I've been handling it rather delicately, but was able to wash it under running water and scrub it with a toothbrush to get off the remaining powder.

I guess I'll be trying to fire the fiber-porcelain today.

I drilled a peep hole in order to gauge better what's going on inside.


Soon after, though I noticed a glow coming from the back side of the kiln


Turning it around, it seems a hot spot had burned right through the plaster and Perlite dome


Regardless, I just turned the kiln around and this seemed to do away with the hot spot, or moved it to the other side.

I was working outside as this whole microwave kiln business seems to generate some odor, however a sudden squall passed through with high winds and then it started to rain so I decided to call it quits.

Hopefully the displacer got fired well enough anyway.

The fiber clay displacer seems to have survived


https://youtu.be/UvHjKzlKc0o


Generally speaking, it seems like it could make a good fireproof displacer. Seems strong enough and fairly light.

Though, in actuality, the original foam displacer this is intended to replace weighed in at about 3 grams. This porcelain "paper clay" displacer, though after sanding smooth is only about 1/2 the thickness weighs in about 10X heavier (31 grams)

I was using internet search, trying to find information about using Drexel foaming agent with porcelain clay and an interesting expired patent came up in the search results.

https://patents.google.com/patent/US4328034A


Reading through the patent, this mineral foaming formula seems potentially ideal

The ingredients are pretty common and fairly inexpensive. Easily obtainable anyway.

The process seems pretty straightforward, along the lines of "elephant toothpaste". With the difference that after expanding this hardens into a strong lightweight mineral foam that can withstand the heat of a welders cutting torch (5000°F) and could also be further strengthened by incorporating fiberglass (or perhaps carbon fiber ?)

It does NOT require firing in a kiln.

The only ingredient I don't have on hand is silicon powder which I just sent for, and I also needed a hydrometer for the water glass solution.

The patent related that the hardened foam can be cut with a "hand saw", to remove excess, such as due to over expansion.

So, just mix together the ingredients and let it foam up into a mold or whatever and harden.

It also adheres to metal.

The silicon powder may take a while to get here. I was going to order some from a company in Texas, which would have been quicker, probably, but they wanted $25 for shipping of just 100 grams which seems ridiculous.

While I'm waiting for the silicon powder to arrive, I'll continue experimenting with the Drexel F.M 160

Waiting for that blob to dry, which is just a small batch I made with the kitchen blender.

Still don't really have a clue what I'm doing. Just put some water in a mixing bowl, turned on the blender and added Drexel a drop at a time until it made what looked like a good foam, then sprinkled in the dry Portland cement until it thickened up. At that point the volume shrunk down about 2/3rds. Not sure if that's supposed to happen. Did I add too much cement?

BTW, I made a mistake earlier in regard to this stuff:


That was not silicon carbide. I mean, there was no silicon carbide. I was trying to see if I could MAKE silicon carbide foam. I had actually crushed up some anthracite coal and mixed that with the sifted Perlite. It was so spur of the moment and random, by the time I finished firing it in the kiln I had forgotten I did not actually put any silicon carbide in the mixture.

The results did LOOK a lot like foamed silicon carbide though. Enough to fool me into thinking the silicon carbide I added had turned into foam, but actually I had only put crushed up anthracite coal in the mix.

So... In a way, that experiment turned out kind of interesting. Still not entirely sure what that stuff is, a kind of black, fireproof foam. And pretty strong. I used in as a platform to fire the fiber clay on in the kiln. A pice of it did eventually break off but considering it's pretty paper thin and was fired in the kiln twice it has held up pretty well.


It slumped a little while firing the porcelain

Here it can be seen under the kiln paper being used as a platform.


The big clay disk under it exploded in the kiln. The kiln itself melted, so considering all it's been through, whatever it is, it's held up pretty well.

The fiber clay looks quite good as well, but at 30 grams, still heavier than I would like, the black anthracite/Perlite stuff is just 12 grams.

After about 6 hours or so, the aircrete had to be moved off the dinner table. We were careful with it, but ..


There is another sample on the kitchen counter that has not been moved. Still don't know what I'm doing wrong. Normally pure Portland cement gets extremely hard very quickly.


I'm finally getting around to the paper clay made with newspaper and toilet paper mixed into high fire English porcelain clay.

While at it I decided to try the lost spaghetti noodle technique. I also brushed on some paper clay "glue" (watered down paper clay) between the layers of clay and noodles.

Looks like it has some potential so far. The partly cooked noodles were pretty easy to trim away, but I might cook them a bit longer next time.