Jules Posted January 24, 2012 Report Share Posted January 24, 2012 Hi Everyone, Newbie here with a question for experienced ceramicists. Serious, I'd like to make small pieces say from chicken egg to 15cm diameter max round / ovoid shapes using pinching to bring them to a fully sealed internal void. I've got the technique exac how I want it for constructing BUT my Tutor won't let me go ahead with firing pieces without holes pricked. The SOLE concept of this idea is to force the air out, creating whatever damage it may on the piece. My thinking is that as long as I keep the clay thin = less than 5mm and possibly ever so slightly uneven, this will simply push the air through the weakest point(s) and make a sort of 'forced hole' and / or cause the piece to crack apart - that is the exact point of what I want to achieve. I have a safety box for putting my work in the kiln. However, Tutor is saying more along the lines that doing suchlike would be called making a b*mb and is totally disimpressed not to mention kiln techs at my college and they won't even coutenance the convo. I feel misunderstood. Surely some air escaping (albeit forced) is just going to kind of *ahem* 'blow out' and affect the individual piece not actually blow up the entire college and wreck the kiln....... PLEASE can someone help me make a rational proposal to my Tutor and back it up with some science or something...... Cheers ** dodges bricks from lab techs and ceramics tutors ** Would like to point out I'm over 40 not under 14 and I take my conceptual work very seriously! Link to comment Share on other sites More sharing options...
Guest The Unknown Craftsman Posted January 24, 2012 Report Share Posted January 24, 2012 I think the concern might be that the pieces might not be fully dry, and might explode. See this thread for help with that : http://ceramicartsdaily.org/community/topic/1771-options-for-drying-clay/ Trapped DRY air will never cause an explosion. Air molecules are much smaller than the space between clay platelets, or even the molecules, and will move freely out of the piece. In fact, Nils Lou once wrote an article advising people to make pieces with air filled voids in them, and to fire them right next to their important work that was needed for an important exhibition. That's how confident he was in this fact. The pieces you want to make sound as if they would dry readily, and should not be a big deal. Just for curiosity, what cone will you be firing to, and what kind of 'safety box' do you have? I could see rigging something up with small kiln shelves. but I think it's not necessary. Link to comment Share on other sites More sharing options...
Chris Campbell Posted January 24, 2012 Report Share Posted January 24, 2012 Well, you will be interested in the work of Steve Tobin ... he has blown up pots and has videos of him doing it ... a few years ago so I don't remember how he did it but he used the results very successfully in fountains ... Google him and see if you can find it. He works outside Philly and is well known. Link to comment Share on other sites More sharing options...
FBL Posted January 24, 2012 Report Share Posted January 24, 2012 Hi Everyone, Newbie here with a question for experienced ceramicists. Serious, I'd like to make small pieces say from chicken egg to 15cm diameter max round / ovoid shapes using pinching to bring them to a fully sealed internal void. I've got the technique exac how I want it for constructing BUT my Tutor won't let me go ahead with firing pieces without holes pricked. The SOLE concept of this idea is to force the air out, creating whatever damage it may on the piece. My thinking is that as long as I keep the clay thin = less than 5mm and possibly ever so slightly uneven, this will simply push the air through the weakest point(s) and make a sort of 'forced hole' and / or cause the piece to crack apart - that is the exact point of what I want to achieve. I have a safety box for putting my work in the kiln. However, Tutor is saying more along the lines that doing suchlike would be called making a b*mb and is totally disimpressed not to mention kiln techs at my college and they won't even coutenance the convo. I feel misunderstood. Surely some air escaping (albeit forced) is just going to kind of *ahem* 'blow out' and affect the individual piece not actually blow up the entire college and wreck the kiln....... PLEASE can someone help me make a rational proposal to my Tutor and back it up with some science or something...... Cheers ** dodges bricks from lab techs and ceramics tutors ** Would like to point out I'm over 40 not under 14 and I take my conceptual work very seriously! Link to comment Share on other sites More sharing options...
FBL Posted January 24, 2012 Report Share Posted January 24, 2012 Sounds like an excting experiment. You might want to try firing it as a Raku piece as you can control the firing enviroment. Is your tutor concerned that if your piece explodes it would harm the kiln or other pieces? If so, I'd find another place to fire or try to buy my own kiln. Link to comment Share on other sites More sharing options...
Lucille Oka Posted January 24, 2012 Report Share Posted January 24, 2012 Try firing them in the kitchen oven to see if you can explode them there. But If they do explode they may make a mess of your oven. I had to re-read your post I misread it originally. I hope you will achieve what you are after. Link to comment Share on other sites More sharing options...
Guest The Unknown Craftsman Posted January 24, 2012 Report Share Posted January 24, 2012 I think I am with Lucille in that I mis-read your post as well. If you WANT your pieces to explode, that's different! After watching Steve Tobin do his work, it doesn't seem like it is something that could be adequately handled IN the kiln. Tobin Blew his pieces up while still soft, then fired the results. There is a youtube video of that here : Also, in the career retrospective book Steve Tobin: Natural History, there is a DVD included which shows him exploding clay, installing sculptures, etc. I read it in 2008, it's very good. Also, see some of his exploded pieces here: http://www.stevetobin.com/clay.html Some of them remind me of the egg pods from the "Alien" movies. Link to comment Share on other sites More sharing options...
TJR Posted January 24, 2012 Report Share Posted January 24, 2012 Man, the stuff you learn on this blog! The problem your teachers have with you blowing stuff up in the kiln is that it will break other work beside it and also make gravel shards which have to be vacuumed out of the bottom of the kiln. Does anyone remember a Romanian artist who used to shoots blocks of raw clay with a rifle. I think it was in Studio Potter.[ Pre youtube days] He used to then fire the blocks of solid clay for a permanent sculpture. I have not tried any of this. I try NOT to blow up my work. TJR. I'm over 40 as well. Link to comment Share on other sites More sharing options...
lacemuse Posted January 24, 2012 Report Share Posted January 24, 2012 I loved Steve Tobin's video! Makes me want to blow stuff up!! I've been known to paint shellac on encaustic paintings & light them on fire... OK, I think that's what you want to do (Steve's approach,) but on a smaller scale. Here's an idea. If you have a compressor available to you, maybe you could put the end of the hose just into the oval piece, seal it real good so no air leaks around the edges, then blast air into it. You could adjust the air pressure & test on soft & leather hard clay to see what works best. If you can't get your hands on an air compressor, maybe a bicycle pump would work. I may have to try the bicycle pump - sounds like fuuuuuuuunnnnnnnnnnn! I blew up a bowl in the kiln - NOT pretty - damaged another piece & it was a mess to clean up. Link to comment Share on other sites More sharing options...
metal and mud Posted January 24, 2012 Report Share Posted January 24, 2012 Now that was fun!! I like to read the Forum postings at lunch time at work. Reading this thread and viewing the Steve Tobin video will keep a smile on my face all day!! Link to comment Share on other sites More sharing options...
teardrop Posted January 24, 2012 Report Share Posted January 24, 2012 The problem your teachers have with you blowing stuff up in the kiln is that it will break other work beside it and also make gravel shards which have to be vacuumed out of the bottom of the kiln. The OP stated that they had a "safety box" made to encase the work to prevent damage to anyone else's work should the peice explode....so I'm not seeing what the problem is with the request/experiment. Link to comment Share on other sites More sharing options...
Jules Posted January 25, 2012 Author Report Share Posted January 25, 2012 Thanks for the answers everyone - I haven't got time to reply individually but love this forum and yay Tobin's stuff is great! Am considering using microwaive with wet clay to see what would happen .... will report back (hopefully not from hospital or under a pile of rubble that used to be my flat). Also a few other experimental ideas forming, or unforming as the case may be... Jules Link to comment Share on other sites More sharing options...
Christine Posted January 25, 2012 Report Share Posted January 25, 2012 Now that was fun!! I like to read the Forum postings at lunch time at work. Reading this thread and viewing the Steve Tobin video will keep a smile on my face all day!! Oh me too! I had never heard of nor seen Steve Tobin before - it makes me want to go buy explosives ..... and I'm over sixty! Thank you so much for this post Link to comment Share on other sites More sharing options...
macdoodled Posted January 25, 2012 Report Share Posted January 25, 2012 small (wet clay ) exploded piece then bottom shaped - using firecrackers. Wear safety goggles and use a trash can cover to shield from explosion at minimum. PS: Make sure it's legal or you get a permit where you live , or you could get arrested. Also - We have had exploded clay in my class when some did sculptures too solid or no air holes, both were determined to cause it . I have a piece with someone else's exploded clay (in cone 10 glaze fire?!?) stuck to it Link to comment Share on other sites More sharing options...
neilestrick Posted January 27, 2012 Report Share Posted January 27, 2012 AIR BUBBLES WILL NOT BLOW UP. TRAPPED AIR WILL NOT BLOW UP. STEAM BLOWS UP POTS. This is why you must fire very slowly at the beginning of a firing, to drive off any remaining water before it turns to steam. Even bone dry pots have a small percentage of water in them, just like kiln dried lumber has 6% mosture. The thicker the piece, the longer it takes for the clay to warm up, and for the water to evaporate. It has nothing to do with air. Closed pieces, or those with only small pinholes, take much longer to dry. They will feel dry on the outside but still be wet inside. Link to comment Share on other sites More sharing options...
Frederik-W Posted January 28, 2012 Report Share Posted January 28, 2012 I agree with Neilestrick, not because I have pottery experience, because what he says makes scientific sense. Trapped moisture will turn into steam and build lots of pressure. Heated air can escape more easily, does not build as much pressure. From an aesthetic point of view, I cannot see why exploding it will make it better than just throwing it against a wall or dropping it on concrete. What you will end up anyway is with a lot of broken pieces. Perhaps much easier to fire a couple of objects and then breaking them in different ways till you get the effect you want. If you want cracking and not exploding, it would be better to rapidly cool it as is done in Raku. If you want an explosion, what about making a fire and chucking a half-green piece in the hot coals ? Link to comment Share on other sites More sharing options...
neilestrick Posted January 28, 2012 Report Share Posted January 28, 2012 Shards in the kiln are an issue. When they land on elements, they create hot spots that can burn out the element. They must be completely vacuumed out after the firing. It can be difficult to get out every little piece. Those that remain will cause the elements to wear faster. Link to comment Share on other sites More sharing options...
Guest JBaymore Posted January 28, 2012 Report Share Posted January 28, 2012 If you look at the Gas Pressure Laws, and assume that the enclosed clay form was made at atmospheric pressure (1 atm.) and on a 75 F day (296.9 Kelvin), then you look again at about Orton Cone 9-10 (1577.4 Kelvin), the volume of the gas you originally trapped inside the interior of the form has wanted to expand to about 5.3 times the original volume. Assuming the volume of the clay container does not change (see below) the pressure within the clay object then also increases about 5.3 times. Technically the original clay object has shrunk from the fully wet form when the air was "trapped" as is dries, and it is also shrinking as the clay body matures in the kiln. So the pressure change would actually be a little bit higher than that predicted above. BUT... and that is a huge "but"......... that all assumes that as the gas pressure inside the fixed volume of the clay form increases with increasing temperature, the air inside is actually completely "trapped". Clay walls are somewhat gas permeable to the molecular sizes of the components of air (mainly oxygen and nitrogen). So as the pressure comes up a bit, SOME of the "trapped" air volume is actually escaping right through the supposedly "solid" clay walls. It is only more toward the vitrification point (when the clay is developing significant glassy phase) when the walls are becoming more "solid" as far as the outward movment of air molecules is concerned. So that fivefold theoretical increase in pressure on the interior surface is not really happening. It is something less than that, spread over the time of the entire firing. So the question comes down to, "How strong is a given clay wall when pressure is exerted evenly across its surface"? How much pressure differential can an enclosed form tolerate? For a given clay body this strength can be predicted a bit by looking at the M.O.R. for the given clay body. (Modulus of Rupture) But staying more non-technical and looking at empirical evidence, as has been mentioned already above, experimental data (from many people deliberately trying it) supports that the pressure is not enough to cause the clay walls to typically rupture. HOWEVER... and that is a big "however"........... it is VERY easy for liquid water to remain or to migrate into the enclosed spaces in a form. So closed forms tend to trap some moisture inside unless dried VERY lsowly over long periods of time (or dried in a ceramic dryer unit). If when heated they are not FULLY DRY inside that enclosed space, a tiny amount of liquid water at the state change happening at 212 F turns into a much larger volume of water as gaseous steam, thereby increasing the interior pressure at a point where the clay walls are pretty darn fragile. At 212 F when the state change from liquid to gaseous occurs, the volume changes 1603 times. Picture a single drop of water. Suddenly that single drop requires the space of 1603 drops. BOOM!!!! At that same 212 F point, expansion of the trapperd air from the original 75 F forming time has increased the atmospheric pressure inside only to 1.3 times the original pressure. Pretty insignificant change. It is about the water. best, .................john Link to comment Share on other sites More sharing options...
neilestrick Posted January 28, 2012 Report Share Posted January 28, 2012 Nice not-too-technical explanation, John. It's good to hear some actual numbers. Thanks. Link to comment Share on other sites More sharing options...
Frederik-W Posted January 29, 2012 Report Share Posted January 29, 2012 Thanks John, for the technical insight. It continues to amaze me that ceramics is not just an art, but has so many different aspects to be aware of, including the technical side of it. You can never learn enough. Link to comment Share on other sites More sharing options...
Jules Posted January 30, 2012 Author Report Share Posted January 30, 2012 Hi, again, thanks so much for all the considered replies... they're really helpful. Yup I'm in the mood for blowing things up - I don't think my college will be able to facilitate such madness. Therefore I'm considering mini-dynamite a la Tobin by the way of firecrackers or suchlike (not performed on college premises in case my Tutor reads this). Also am considering buying a microwaive, putting green chicken egg sise (<bottom left of keyboard doesn't work so have no see / sed key) inside a microwaive bag and seeing what happens. I would like the results not to look like they were just smashed up as that would defeat the purpose. Am also wondering what happens if you boil green clay with an air void in plastic bag in a pan of boiling water. I feel a very messy(messier) kitchen coming on. Will post results when have tried. 1603 BOOM! Love it...... Have a great week everybod Cheers ~ Jules Link to comment Share on other sites More sharing options...
ayjay Posted January 30, 2012 Report Share Posted January 30, 2012 I feel a very messy(messier) kitchen coming on. Will post results when have tried. 1603 BOOM! Love it...... Cheers ~ Jules Jules, you sound as mad as a box of frogs - looking forward to seeing the results. Link to comment Share on other sites More sharing options...
Paula Patton Posted January 30, 2012 Report Share Posted January 30, 2012 Did we ever cover the saftey box? I can only picture building a large clay box, but it would break too if something inside blew up. Please post some of your experiments, maybe we all need to blow something up! Link to comment Share on other sites More sharing options...
JLowes Posted January 30, 2012 Report Share Posted January 30, 2012 Jules, bear in mind that if you explode your clay egg in a pot of boiling water, that it is likely to generate a tsunami .. ;-) .. of boiling water flying through your kitchen. I would not want to be in the kitchen at the moment of the explosion. On the other hand, maybe it will not do that. Just in case, where should we send flowers? I can tell you from first hand experience that the steam explosion in a kiln creates hundreds of little fingernail sized shards, and those can break up other pots around it. Now for a bisque firing I candle overnight, with an open lid and a couple of kiln shelves to keep some heat in, and start the rest of the firing in the morning (no computer controller on my kilns.) John Link to comment Share on other sites More sharing options...
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