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glinum

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About glinum

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  • Gender
    Male
  • Location
    Ukraine
  • Interests
    Pottery, gardening, family
  1. Why It Goes Off Center?

    Thanks everyone again! And special thanks to Pres for the detailed critique. I don't know why I paid no attetion that I'm opening too wide and then try to narrow the form while pulling up. That's weired... I know about even pressure etc., but I noticed that the top starts to wobble when I begin to pull at an angle to make a round form and it starts from the very base of a pot (like JLowes said) And if I can make a full pull to the very top it will recenter the form, but with this particular form I couldn't do it because I wanted a narrow neck and obviously the full pull would ruin that neck.
  2. Why It Goes Off Center?

    Wow! Thank you guys for all the advises. I will keep practicing and update this topic later, hopefully with better results My wheel is DIY wheel made by someone who has no clue about pottery. It used to have very very little torque. So I made new pulleys to increase the ratio and as a result it increased the torque, but still not enough. I just make the wheel to spin faster so when I center the clay it spins with adequate speed. The bat is off center but it sits on pins and doen's move, so it's not a problem. I use bats so I don't have to squeze a bigger piece while removing it from wheel head. Just to make it clear can someone explain what is collaring? (I'm not a native english-speaking)
  3. Hello! I've been doing pottery for more than a year now, mainly with smaller forms. Now I'm learning to throw with bigger lumps of clay - 1.5kg to 2.2kg (3.3-4.8 lb). The problem I'm facing is that the top of a pot goes off center when I'm widening the walls. So I center the clay, open it, pull up the walls to make a cylinder. Then I start to stretch the walls wide from the bottom and at this pointer the top of my pot begins to go off center and the more I widen the walls, the more off center it goes. I just can't understand what am I doing wrong? The funny thing is doesn't happen all the time. Sometimes the top stays in place when I stretch the walls. I would be very thankful if someone could watch my and tell me what I'm doing wrong. I think I have to mention that I'm a selftought potter, I just watched Simon Leach's videos and did what he did.
  4. Sometimes I see pieces with different color blends in glaze, it's like one color runs smoothly into another one usually in a chaotic manner. It's hard to explain, here's a picture of what I mean: I have clear glaze and some color pigments. What's the process of doing this things? Do I have to stir a pigment with water, apply it to a piece and then cover with glaze? Or do I have to mix a pigment with glaze and apply it in one layer and then do the same for other colors? I never did glazing, just learning things. Thanks.
  5. Hallelujah! I finally sorted it out. The reason was quite simple - I had to throw away the pressure reducer. For some reason I thought it's not ok to run a burner without it, but I talked to another Ukrainian potter who uses similar setup and he said he runs it without the reducer. So no other tweaks were actually necessary if I got rid of it on my very first firing. The burner size was ok, the holes were ok, the flu, the draft etc. were ok. I climbed to 1040C/1900F in about 8 hours and the burner was only 70-80% open, so I believe I could easily climb to 1250C/2280F if I wanted. But I was firing earthenware so 1040C/1900F was just fine. When I opened the burner some more the reduction flame ran out the top hole. That is so exciting! I didn't actually need it for bisque firing, but now I know I can do reduction firing if I want. Check out the . Here is the picture of the fired pieces I made this morning. I have some questions about color changes but will post it later in a separate topic. This is what happened to the shelf: Probably it will live a few more firings and then I'll buy some good kiln shelf, because this one is not. So this topic is now in resolved status Thanks to everyone who tried to help, I really appreciate this. Andrey
  6. bigDave, thank you for the encouragement, it really helped, especially about the chosen ones! So the next day I decided to decrease the kiln inner volume by putting a fiber wall about 2/3 from the front lid and cut the shelf on half. And I didn't put too many pieces in there. So I noticed that the temperature climbed much quicker than before. I got to 500C/932F in about two hours, but then again it just stucked. So I thought what if I somewhat close the top hole. I used some pieces of fiber and and made the hole about 7cm, while it was 10cm. I also closed bottom hole a little. To my surprise the temperature started to climb! I also tried different burner positions and noticed that it should not be too far out, just about inlined with the entrance. So in about 2.5 hours I got to 700C/1292F. Then it stuck again so I closed the top hole even more and it started to climb! In another 2 hours I got to 850C/1562F. And it seemed like a limit because no tweaks I tried helped. Anyway I was so happy even with this result The pieces were glowing orange, what a joy So the conclusion is the holes should not be big and the pieces should not be packed to tightly. I think there's some perfect proportions for the holes I'll have to find. The next day I went and bought a bigger burner with side holes. I also wanted to buy a splitter to be able to connect two burners, but couldn't find it. I removed the wall in the kiln and reverted to original volume. Everything went fine, but at 800C/1472F it stucked. So I inserted the burner more in the hole (it was about 2in away) and it climbed to 850C/1562F and wouldn't climb any more. Maybe the shelf is making problem? It's actually an insulation board and it doesn't heat up like a special kiln shelf should. Mark, you are right, I know about the tank freezing, I put it in a water container and added hot water there.
  7. Mark, I agree that the burner is too small. I think I'll have to buy a bigger one. Or maybe I can have two of the same size? Is it ok to fire two burners from the same tank? I worry that the pressure will split between two burners and it won't give any difference. Maybe I have to get two burners and two tanks? I just did a test and boiled 1liter of water with fully open burner. It took 4m30sec. Can I estimate burner BTU with this information? We don't use BTUs here because we use metric system, so I don't really know how to calculate and convert it.
  8. Today I fired it again and couldn't even reach my previous result of 650C, now it climbed to 600C only. :-( I am so disappointed... Anyway, this is what I did - made both holes bigger (especially the top one) and pull the burner out oh the hole. In 5 hours it climbed to 520C/968F just fine and then stalled... 2 hours more and only +20C. Then I decided to cut the top hole even bigger and pulled the burner even more out. It then raised to 600C and stalled. I tried everything - adjusted the burner to different positions, I tried to blow some air with a room fan, I even found some oven chimney pipe and inserted it into the top hole, but that actually dropped the temperature to 550C. I ran around for almost 12 hours and nothing helped, so I just turned the burner off and feel very bad now. Don't know what to do... Maybe I have to switch to vertical design? Or maybe I have to switch to woodworking...
  9. neilestrick, chimney?? Oh no.... I hope I'll make it work without it. This is a low-end project and chimney will ruin the whole concept But in case I decide to make one, what would be the height of it? Marcia, the shelf is 40x60cm and 10cm away from the back wall, do you think that's enough? INYA, pictures would be great! Thanks
  10. Wow, INYA, so much helpful information in your posts! :-) Thank you! Now I'm eager to start firing again with this tweaks. I do understand reduction, I just didn't understand what justanassembler meant by "you are reducing too hard" and what that pratactically means, what I was doing wrong for "reducing too hard". Now I know it was because I inserted the burner in the kiln so it wasn't able to suck enough air and also the top hole was too small. Do you mean the top hole or some extra hole? I have the top hole, check fire8.jpg in my first post. I put some rocks there just because I didn't know it must be bigger and not smaller. Now I know I have to make it bigger. Do I have to make the bottom hole bigger too? Was it becase the gas tank freezes or because your kiln surface loses too much heat?
  11. Thank you for all replies! The shelf is not actually a kiln shelf. They sell carborundum shelves for $100 and this one was $9 for the same size, So I bought it. They actually use these to insulate heating stoves. This text was originally in russian, I hope I translated it correctly. The problem with this plate is that it has very low thermal conductivity, it just doesn't heat up on top if you drive flame on the bottom. So I had to drill many holes in it for better air circulation. It seems that the heat is distributed quite evenly in the ware because there are no color spots on the pieces like I had in a wood kiln. Here's a diagram I made quickly to show how it works (in theory). Sorry, I don't really understand what that means... Marcia, here are some pics of the burner It's just some simple burner from ware store they use for roofing etc. The BTU rating - have no idea... It seems Simon Leach uses similar burner but with some side holes. And I just noticed in his video that the burner is all the way out of kiln while I stupidly inserted it inside... So could it be a problem that it lacked oxigen? The top hole was open, but when the temperature stoped climbing I thought maybe it looses to much heat so I closed it a little with some pieces of brick. Can you explaine a little about a better flu system and better draught with a chimney. TJR, yeah now I see that the burner had to be completely out of the kiln, that was the problem... I don't have any cones as I said earlier just because they don't sell it here. I determine the temperature with a thermocouple. justanassembler, I agree about the burner. I just didn't pay attention how people do it. Next time I'll put it otside the kiln and point the flame in the hole. Do you think I have to route some side holes in the burner? And I still need to understand if this single burner is enough for heating up 30gal kiln? Or maybe I need to cut some volume and make it smaller? I got some off topic question - if I fire red and white clay in one load will there be any color blends? I tried it once in a wood kiln and white clay pieces came out darker, but maybe that was just because of ash or something?
  12. Hello! I'm a beginner potter and still learning things. I was inspired by Simon Leach to make a similar . I decided to go for this type of kiln because I thought it's simple to build and chip. I made it in a metal drum instead of Simon's welded wire.The inner volume is about 115L (30gal) . It's covered with the 50mm (2in) ceramic fiber inside. I used a regular burner from a hardware store and 50L propane tank with reducer that people use in households here in Ukraine. Also I inserted there a thermocouple connected to some simple multitester with TEMP. Cones seem to be very hard to find here and expensive ($1 each, 400pieces min lot) So I loaded some ware and started my first firing. In the first hour temp climbed to 230C/446F (valve 50% open). In next 4 hours (valve 100% open) the temperature climbed to 650C/1200F and stopped. I waited for another 1.5 hour ans then gave up and turned it off. I think I need to mention that I fired outside and it was a little windy but that didn't affect the burner. The air temp was about 12C/53F. I put the gas tank in a container with hot water so it was not freezing. The outer surface of a drum was very hot. I could touch it, but not hold my hand there. Can someone suggest why this could possibly happen? Simon says he gets 1000C/1832F in 3 hours. So I must be missing something in my setup. Here's my guesses: 1. The kiln volume is too big for a single burner. 2. The ceramic fiber layer must be thicker. 3. The drum must be placed in some insulation. Maybe put it in a box and cover with sand (leaving the front face open of course)? 4. The gas tank pressure is not enough (thou I don't really think this could be a case). I attach some pics. Another question is if it's ok to refire the same ware again to get to 1000C/1832F?
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