Plaster of Paris and sand mix

[Glenn]

DO NOT use Plaster of Paris and sand mix for a forge.

Let me say that again:

DO NOT use Plaster of Paris and sand mix for a forge.

 

Read the discussions as to why it is a bad idea by clicking on the link. Click here.

[Sardonicus]

I know kilns aren't exactly forges but my questions are regarding refractory mostly and I know people here will be very knowledgeable in that realm. 

I recently saw a video that mentioned using plaster and sand as a refractory for their kiln, and after a bit of looking around mostly what i see is a few brave souls that have just gone and used it without much detail on performance or longevity, and then the other side of that coin all the people shaking their heads saying its just bad for use as a refractory with a moderate chance of exploding. I assume this explosion chance is due to moisture. 

I am working on a hydrogen project and as part of my project I need a fairly sizable amount of graphitic carbon nitride, stupid expensive to buy, but very easy to make - assuming you have a kiln. So my actual question - could plaster and sand be used in a device intended to reach 600C. For doing what I want I really only need to get to 500 - 550C max. I am mostly wanting to use this because it is cheap and the kiln I want to make will be quite large. For the final stage of my project I will need 10kg of the graphitic carbon nitride , I dont expect to be able to build a kiln to make that kind of volume all at once, but I'd rather not have to do it in a thousand tiny batches either. 

Now, cheap is a big determining factor in what I can use , but not at the cost of safety, so I am definitely open to suggestions on other economical refractory options that are safer. If such a thing exists. The device itself is electric in case that matters. For size I am considering about half to 3/4 of a 55 gallon drum. I would like to insulate the floor and walls, have a door in the side and probably firebrick on top. 

[ThomasPowers]

Can you explain how spending many more dollars in energy costs saves over spending fewer dollars in refractory costs?  The "I spent 400 dollars extra on fuel to save 100 dollars for proper refractories" dilemma.

Plaster of Paris specs "When heated to about 200 C, it loses all its water of crystallization. It does not recombine with water after this stage and is said to be dead burnt. Above 400 C, it decomposes into calcium oxide."   Engineering 360  "Properties of Cement and Cementing Materials"

So expect to replace it if used at your wanted temps and as it's NOT A GOOD INSULATOR; expect to have to waste a lot more BTU's using it.  I actually think it might be more expensive to build than using commercial refractories for a larger sized kiln.

Have you looked into buying a used ceramic kiln?  I see them for sale pretty cheap on a regular basis.

[Latticino]

+1 on used ceramic kilns.  I see them all the time and it is pretty easy to fix one up if not functioning if the bones are there.

[Frosty]

Experimenting with photoelectric generation? There are a lot of well funded organizations in the field already or are you doing it for fun? Graphitic carbon nitride has potential but is a long way of real breakthrough away from being a practical solution to solar energy being efficient, effective and economical. 

I don't know much about direct solar electric conversion so I looked it up in regards to your project. It seems it's considered "promising" and worth more research. Do you have a break through idea or are you ready to spend big money in competition with the big boys and universities?

I'm not saying not to go ahead on it I'm curious if you have more than a bare idea.

Frosty The Lucky.

[Mikey98118]

Thomas and Latticino have the right idea.  My last two electric powered ceramic kilns cost zero dollars for both of them. Get in rid of them when I was done, also cost zero dollars 

[Irondragon Forge ClayWorks]

Stop by my shop, I have a propane fired four burner ceramic kiln, that I would make you a real deal on.

[Sardonicus]

I would love to buy a kiln that needs a bit of fixing up, but I can't find any in my area. I found a few but never got any responses from the sellers. 

 

I'm not overly concerned about the energy consumption, I also play around with lifepo4 battery packs and solar so either way the energy is essentially free. I do understand what you're saying about why plaster is a no go and will look into a refractory source locally if I opt to build before I get lucky and find one cheap or free to fix up.

 

Frost, I'm not looking into photoelectric generation, and all this experimentation is just for fun. There is a variation on graphitic carbon nitride that is suppose to hold 10% hydrogen by weight at ambient temperature, so my plan is to build a moderate sized dry cell setup to keep the gasses separate so I can expose this stuff to straight hydrogen and then play around with fueling small engines with it. Might work, might not, it'll be an interesting journey either way. 

 

Arkansas would be a bit of a trek for me from georgia, Irondragon or I might well take you up on that lol. My chickens don't give me much free time for travel, I've got 20,000 of them lol.

[ThomasPowers]

I can't believe Georgia doesn't haver a kiln or two languishing in somebodies garage---have you gotten off the computer and tried the TPAAAT yet?   There was a boom in home ceramics a couple of decades ago and after that passed a lot of kilns went into "dead dog storage".

Large kilns are energy hogs be it NG, Propane or Electric---how much solar do you have?  I keep getting calls trying to sell us solar out here in NM; but they hang up when I start asking about running multi horsepower motors off it in my shop.   (The India call centers with folks using fake "American" names sure makes one want to spend $$$$ with those companies; "we're lying to you upfront, why don't you want to spend $$$$ with us?"

[Sardonicus]

tpaaat?

I only have about a KW for solar for charging some pretty fun battery banks, nothing too extensive, but the uses i have for a kiln are limited so im thinking for the few hours here and there work that I have for one that my energy costs would be pretty small. 

[Glenn]

Thomas Powers Applied Anvil Acquisition Technique (TPAAAT)

 

TPAAAT got 630 hits on the site, so some reading may be in order.

[Sardonicus]

Ah, no lol I haven't just asked random people. I kind of live in the middle of nowhere and dont see other people much but that did get me thinking. Seems like there are small family run pottery places around here in every direction. Might be worth a visit or a few phone calls to see if any of them might have a kiln they've retired and wouldnt mind passing on to a good home. 

[Irondragon Forge ClayWorks]

On 4/17/2022 at 7:59 PM, Sardonicus said:

bit of a trek for me from georgia,

See if you had put that location in your profile, I wouldn't even suggested that. We bought that kiln years ago when we had a pottery business, that is now closed, and we have two electric kilns for the hobby aspect. I thought about taking the burners out of it to build another forge but hate to cannibalize a good working piece of equipment. If I remember right we found that one on Craig's list about an hour from our place for $50 U.S.

[Sardonicus]

My bad, thought I had filled that out.

[Frosty]

We'll forgive you. I used to make a bigger point of putting your location in the header and as it turned out more than one guy turned out to live within about 20 miles of me. In the Mat Su Valley, Alaska. 

One of our guys ended up with 3 old pottery kilns for taking them away. He cannibalized one to make the other two work. One is his go to for making Mokume Gane and the other is his heat treat oven. It just makes the meter hum a happy tune.

Scrounging is an acquired skill set.

Frosty The Lucky.