That's a great experiment Jo! You mad ScienTester you!! I must also add it looks Great I bet you were happy with the results. It reminds me of some of the Finnish i glass that I have.

I didn't think it would stand up to a firing let alone the raku style that you did on the campfire. Thanks for sharing your results with us. Kin

Now it's my time to "WOW"--that's just so cool Jo!!!

I bet this has your mind racing! It has mine clicking and I don't have an oven which does my mind no good whatsoever! Stop it mind!

I was kinda surprised, but as a warm glass artist, I knew vermiculite and perlite can be used to make high fire molds with clays, but portland? Who knew?! I think the flyash would be an excellant addition, don't you? I am planning to do some interesting carvings or castings to slump over, or into, concave or convex. I really like the texture the tufa gives to the glass.
The Mad ScienTester
Jo

Just curious, but how much does a kiln like that cost? Is it good for just glass or glass/pottery? And do you have to have a special type of glass and is it expensive? If you don't want to tell me, that's ok.

I'm thinking that you could make glass parts that "fit" 'tufa parts and make some pretty neat combinations.

The white kiln is a Seirra, fires to 2000f, plugs right into your wall. All or these little kilns are computer controlled so you don't need cones to check the temperature. I paid under $400.00 for it and yes, you can use low fire clays in it, but you have to use low fire clay. You can work with any kind of glass in these kilns. Every kind of glass does something different. For instance, stained glass gets this white film on it and not very suitable if you are just starting out. I use something called 90 coe glass. It melts nicely and doesn't get that nasty white film, and you can melt it together. When fusing glasses together they must all be the same coe number.
I have this kiln too, (see link) and I highly recommend it, and the two-lasses are really nice and helpful people and sell glasses and tools.
If you are really serious, ask me any questions you want cause I could go on all day about tufa and/or glass!

Jo

Here is a link that might be useful: kiln

Jo,

That is way too cool. I would have been afraid to try this, in the campfire or the kiln either one. I read somewhere that perlite and vermiculite will explode if overheated. I guess you proved them wrong huh? How in the world did you manage to chip out the 'tufa without breaking the glass?

Are either of the kilns you use suitable for firing clay, or paperclay, or are they just for glass?

Thanks for sharing this wonderful experiment. It does open up all kinds of new ideas.

Amy

Amy, you can fire anything that takes up to 2000f to fire. I use it for glass, obviously, low fire clays, PMC which is really cool (clay that turns to silver), and now tufa. I don't think you fire paperclay. It air hardens.
The tufa, after the second firing, became brittle enough to be chipped out, which was a happy benefit. If the glass flowed in a more controlled manor, I could have just lifted it off, but it flowed into under cuts so it wouldn't come off so easy. I sprayed the tufa with boron nitride so it would release.

So glad you are all enjoying this as much as I did. this is just the tip of the glassburg.

Jo

Hi Jo,

Thanks for the info. Am I wrong in thinking that paperclay can be air-dried or fired. When fired the paper burns out and leaves a lighter but more permanent piece (or it's always possible I misunderstood). I don't have any experience with this, I've just been reading about it. Information on paperclay is a bit sketchy. I think I'll ask on our new conversation forum if anyone has worked with paperclay.

I will be looking into the kilns. Thanks again.

Amy

This is all very interesting. How long have you been doing this and have you taken classes? I would love to learn more but don't know where to begin.

Amy, I am not sure about paperclay either, but the info I read says air dry. I will be interested to find out too.
mudmaker, I have been playing around with my kiln for about 2 years, took no classes, just research, research, research and playing mad scientester. Now I teach classes on glass fusing. You can begin like I did. Lots of books, silicon folly fusing forum, go to ebay to look at what others have done and for tools, kilns, etc. I am always willing to help out too. Please email me if you have any questions.

Jo

Here is a link that might be useful: fusing forum

Jo,

I think maybe the pre-packaged paperclay is just air-dry, but I want to make my own with real clay. I'm not sure the pre-packaged stuff has any real clay in it. The problem I'm running into is, instructions say to mix clay slip with paper pulp. None that I've found say how thick or thin the slip should be. Does anyone here know?

Amy

Amy, you're not wrong. There is a paper material that can be mixed with clay, & the paper material burns out when fired. I don't know much about it, but I do know that much. I don't know if it is PaperClay BRAND material, but it IS called paper clay.

'Pup

Okay, getting back to fired tufa:

How about using tufa for a chiminea (sp?) outdoors? Build it, let it cure, build a fire inside?

Someone with better weather can try it... Hey, any of you SoCal folks interested?

'Pup

Thanks for info Jo! This is really cool. I'm thinking about it but I have a mile long "want and "I'm goin' to do this" lists that I already have too many tufas in the fire!

What a terrific thread...very interesting to me because I tufa AND because I dig my own natural clay and fire it (in a popcorn tin because I make miniature things). I've often thought about trying to fire tufa too, but like others was advised that it might explode!

The idea of building a tufa chiminea had also occurred to me (just as Pup indicated building the fire inside it to fire it) BUT now I am confused....

Jo indicated that the fired tufa became BRITTLE and then later somehow REHARDENED. Then she used that rehardened tufa piece to slump glass over...and the tufa again became BRITTLE (so brittle that she was able to chip it away from the slumped glass) [Did I understand the process correctly Jo?]

So the question is
"HOW could you FIRE a Tufa Chiminea using this process?"

Wouldn't it initially become brittle, then reharden and then when you went to fire it up again, wouldn't the process repeat itself ad nauseum???

Jo, do you think that the tufa piece you fired would (after repeated firings) eventually become PERMANENTLY brittle???? One would have to assume that firing it over and over would eventually get rid of all the moisture in there and having done that the portland would no longer be able to chemically react/bond and reharden????

Any body have ANY idea where the EXPLOSION factor comes in? I'm sure that the fact that firing concrete makes it explode is NOT a myth...but at what temperature and under what conditions (i.e., it only explodes when it reaches a certain temp? and/or when all the moisture has been driven out????

Ah, sorry for so many questions! The topic really does get ones brain going and like Jo said that can be S-C-A-R-Y!!! lol!

Longlocks
Kathy

Kathy, You are correct about the tufa becoming brittle. It would not be suitable at this time for a chiminea, but this is what I am working on. I am sure I will eventually come up with a "fired" tufa and I think it will be very much like fire brick. The explosion factor must be the water that tufa may have in it. Since I burned out all the moisture in the campfire first, it was safe and ready for a high fire. This piece of tufa was made with peatmoss which also burned almost completely out in the campfire and 100% burnout occurred in the kiln, hence the black look it had at 1350. At 1450 it became white. I will be making a more formal mold for a bowl I will be slumping. I will have to cook all the water out of it first before firing to be sure. Vermiculite, perlite, kittylitter are all used in kilns now, so the only odd ingrediant will be the portland. If we replace the portland with refractory cement, natural clay or a low fire clay, we could produce tufa for fire rings, fireplaces, chimineas, ect. Peatmoss could still be used for creating airspaces for texture and to make it more lightweigh.

Kathy, can you expalin the firing in a popcorn tin thing? I always wanted to fire natural clays. I have a bunch of it across the road at the gravel pit.

Jo

Keep up this experiement, it's so exciting! I too have visions of doing the chiminea thing!
Leigh

Been doing some "X additve" research and came across the link at the bottom & info on firing paperclay. Definitely cool stuff. As for firing a chimenea...there is another site to a sculptor who builds dragons & "firetrees"...he just constructs them from paperclay, then then builds a big--- fire inside. Voila. Self-firing sculpture! See it here: http://www.walihawes.com/

Here is a link that might be useful: Paper Clay Link

Okay, maybe concrete wouldn't be good for a chiminea...

But since we've got experience building stuff with "mud", we could use REAL mud like the Native Americans did/do. They made little ovens ("hornitos") of mud, let them dry, then fired them inside. Many of them still exist on the west side of the California Sierras.

You could make mud bricks, let dry, then stack into a mound. Of course, it would have to be in a dedicated place, & wouldn't be as elegant as a metal chiminea....

But organic material such as peat probably wouldn't be advisable, as it would probably contribute to breakdown.

'Pup

I am not giving up on this. I am researching low fire powdered clays. They can be used just like portland, but will only gather strength with each firing, hopefully. This is not the end, just the beginning.
Tango, great info, and thanks. It's exactly the road I have been taking with this. Instead of papercrete, it will be paperclay. It should have all the properties of the papercrete, but will withstand the high temperatures of a wood fire. Add vermiculite and perlite....oh! Now I am thinking that a fine peatmoss would have similar properties as the paper...hmmm what do you think!
I love those fire trees!
Jo

Jo...As near as I can tell, the trick seems to lie in the nature of the celulose (sp?) fibers. Apparently someone has gotten a patent on a specific "paper fiber/clay" formulation, but as long as the fibers are hollow and suck up some of the "mud" forming long link chains within the mix, it seems to work fine, no matter the type of fiber. One guy stated that newspaper worked as well as anything else he had tried, so I guess the clay slip you mix it with is not all that particlar. It all seems to provide an early set benefit in preventing shrinkage cracks, then burn away during firing, leaving a light-weight fired clay behind. Well, at least that's my limited understanding...and I'm sticking to it.

I missed this little link the first time around.
Very cool fire breathing dragon. I'm also interested in makeing a fire bowl.

Dixiesmom

Here is a link that might be useful: Paperclay dragon

The idea of firing tufa is just silly and down right dangerous
Perlite is plastic and peat is organic.
Both will just burn.
Besides concrete has a bad habit of exploding when heated.
Just ask those guys who thought it would be cheaper to build a concrete wall around their wood stoves.

"Perlite is plastic"???? Huh?

Yikes!
I didn't mean perlite was plastic.
Garden center varieties of 'Perlite' soil conditioners often CONTAIN plastics and other substances that will melt and give off toxic gases and should not be trusted to be fire resistant.

Sorry about the misleading comments.

This info on the dangers of concrete and other 'fireproof' substances like perlite, block fillers, etc came from a Canadian code book on installing wood stoves.
Explosive Spalling of concrete around wood stoves is a dangerous situation. That's why masonary brick must be used instead.
Perlite sold as soil conditioner is not allowed either because of impurities that can melt and give off toxic fumes. In fact perlite can't be used at all even as a block filler around wood stoves because of this hazard.
I included that because most people here are purchasing perlite sold as soil conditioners not a construction grade material.

Perlite in itself is very fire proof.:)

Well, couldn't stand back and miss up on my firecrete thread....
This is the scoop on perlite. Perlite is a volcanic rock. I also fuse glass and we use perlite (and vermiculite) in our forms so the hazards are minimal. Peat is just organics like what you would find in your fireplace logs. I have since fired a tufa tile without explosition and I feel like it is the sponge like feature of cured tufa that keeps it from exploding. I would be sure it is dry. Last summer I tossed in ALOT of tufa mistakes, even wet ones, into my very hot firepit at the campsite and not one item even popped. The peat burns out and leaves many holes for venting in a fire. I am in the process of making a tufa mold for glass slumping. I will post my results. I really love the idea and the tufa gives the glass some interesting texture.

Jo

Jo! There you are--I'm glad CDNDavid flushed you out! How has winter treated you?

Deb

UGGHHHHH, hate the winters here. Was so cold in the cellar mudpit that my tufa won't set up for weeks and when the snow decides to melt and flood the basement, I have molds, rubber gloves, bags of perlite etc. floating all over the place! I'm moving to Texas next door to Dixiesmom. :)

Jo

This is very cool, Jo! It raises another question that's been in the back of my head: Can you use tufa to build, say, one of those clay fireplaces like these:

Or would it get brittle and fall apart?

Hmm, let's try that again...

The fireplace is third one over on the top row of thumbnails.

Here is a link that might be useful: clay fireplace

Hi Jo
I had a neighbor who heated her tiny greenhouse with a commercial hair blow dryer she bought second hand for a dollar.
You could warm your tufa with a light bulb if you put it in a big box, making sure of course that you don't light the place on fire.
People here in -20 below country use light bulbs under a plastic tent to keep their ponds full of fish from freezing.:)

Well, that is a great idea David. I could make curing boxes with light bulbs.
Granny Anna, tufa gets to brittle once it is heated alot. I am thinking about using fire brick first, then covering the outside with tufa. Now, I think that would work just fine, but it would be hard to get that shape.

Jo

I fired my second piece of tufa in my kiln up to 1550 degrees today. No explosions. All the peat and other organics are now burned out of the tufa tile. There was no smoke or smell and the tile is all grey like the color of the portland. I am about to use this as a glass mold once again. I am very excited about tufa as a glass mold and am very sure it is fire safe. It has got to be the peatmoss leaving gaps enough to release any moisture. I will keep you all posted to the results. I used a tile with a leaf imprinted on it. I hope the glass will take the imprint.

Jo

Jo, Post pics of the glass with leaf imprint if it takes. Will these be dichroic? lol Billie

Thank you, Jo. I love the chiminea shape but I think you're right--it'd be hard to get it and still make it usable fire-wise-speaking. Still fun to think about!

Billie ann, I am not using dichroic on this piece. It's still experimental, so I hate to use the expensive glass just yet, but we will find out if the imprint comes out. I fired it today, but without any kiln wash on the tufa. I want to know if it will stick. Should be interesting.
Granny Anna, I really want to tufa the outside of fire brick. It really has possiblities. I don't think it will lose too much strength on the outside, and I guarentee, it will not explode.

Jo

Gottatufa, I recently saw a bathroom sink bowl that was made out of a molded glass bowl--one of those that "sits on the counter but is plumbed at the bottom. Sure reminded me of your experiment here.

Those sinks are beautiful!! Oh, you just got me thinking....one of my fused glass students is a potter with a 24 cubic foot kiln, and she invited me to use it! OH... this can be awesome! Imagine a sink with leaf prints?

Jo

I just gotta say I love the enthusiasum and excitement in this thread!

New ideas flying around, bouncing from one person to another. Too cool!

I don't have a kiln, do anything with glass and have limited experience with tufa, but you guys even have ME excited about this! I can't wait to see the glass and if it has a leaf imprint!

Jean

Lookie what I found! Since you guys are talking about grilling 'tufa again...

Update....(thanks howie) I did slump a square piece of glass over the leaf imprinted tufa. The results were pretty good considering how shallow the imprint was. After this slumping, I took the same tufa tile and carved out a shallow bumpy bowl and slumped on that. That worked fine too and now I can keep using the same form over and over. I plan to make some funky windchimes with this technic.
Jo

Here is a link that might be useful: leaf imprinted in glass

Just was in our local Rona store and saw a product I thought you pyromaniacs would be interested in ... it is a repair compound for chimneys and fireplaces and woodstoves. Just wondered if any of us would use it to 'invent' something tufa-ish with it. The company is Bomix© and the product is called Pyromix. The link is posted below. It should take you to the English page but if not, just go to the homepage and select English, and click on products > repair > Pyromix.

Let's see what will happen with all our brainstorming. Even if NOTHING happens... well we learned that it can't be done, eh? lol

Marly

Here is a link that might be useful: Pyromix by Bomix©

This thread reminds me of David Gingery's booklet "The Charcoal Foundry" about making a home-made kiln. I tried it many years ago. It got hot enough to melt aluminum. I used it to make some molds for casting lead fishing weights and lead-headed jig hooks.

There's a description of the booklet on the Internet -

Click for the site

That is cool Herb, I might look into getting that booklet as I have toyed with the idea of metal casting on a small scale.

Is there an ISBN on the booklet? I might be able to get it through interlibrary loan to peruse it before I purchase.

Marly

Marly - On the back page it has - ISBN - 0-9604330-8-2

Warning - when the thing gets going & you've turned the blower on, there's a spectacular exhaust & rush of sparks from the upper vent hole, and it sounds like a jet engine. We were living on the edge of town at the time, & our lot was over an acre, and we were fairly free to do what we liked on our property, so the noise & sparks didn't matter.

We've since moved nearer the middle of town where there are by-laws regulating outdoor burning. Bonfires for example are completely prohibited. It may be that where we now live, using this contraption is prohibited too.....

Herb

Herb, Give it a try anyway. I'm sure you have friends that'll post bail. Nothing ventured nothing gained. LOL JK ;)

Check out this guy's concrete pizza ovens. Very cool!

Dixiesmom

Here is a link that might be useful: Concrete Pizza oven

Hey, I found this and thought of this posting!!! It is not useing cement, but has possibilities for lining a tufa pit for a backyard fireplace, no? BB

Here is a link that might be useful: fireproof lining with perlite or vermiculite