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tinbucket

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  1. Like
    tinbucket got a reaction from Bill Kielb in Best technique for thin-walled lighting fixture   
    I agree with you that making a mold and slip casting would give you the most desirable result. Any other method will fall short of slip casting when it comes to uniformity and thinness imho. One thing to consider is the heat that can build up in an enclosed light fixture. If you use an incandescent bulb and don't have any venting it will get hot. Also since the form will be round on all sides and translucent porcelain is usually somewhat pyroplastic, you might consider making a cradle of sorts to support the piece in the firing (similar to th way bone china is fired).  Best of luck. I hope you post pictures of the process and results!
  2. Like
    tinbucket got a reaction from PeterH in Underglaze Bleeding Wanted!   
    If you notice both examples of running/bleeding you posted are blue, most likely a cobalt (carbonate or oxide) wash rather than an underglaze. If you are after blue, I would use a cobalt wash rather than underglaze. Unless it is very thinly applied, cobalt will have a tendency to run or bleed. 
  3. Like
    tinbucket got a reaction from Magnolia Mud Research in Underglaze Bleeding Wanted!   
    If you notice both examples of running/bleeding you posted are blue, most likely a cobalt (carbonate or oxide) wash rather than an underglaze. If you are after blue, I would use a cobalt wash rather than underglaze. Unless it is very thinly applied, cobalt will have a tendency to run or bleed. 
  4. Like
    tinbucket got a reaction from JeffK in Defloculated slip   
    Another way to achieve the same thing as adding powdered clay (if you don't have any) is to evaporate some of the water from the deflocculated slip. A wide, low container will give more surface area to evaporate the water and achieve the desired consistency. 
  5. Like
    tinbucket got a reaction from C.Banks in clay plasticity/water content   
    How are you mixing your clay?  Something that has not been mention is that commercial clays are typically pugged in a de-airing pugmill. This alone makes the plastic clay much more dense than if it was mixed to a plastic consistency from dry materials (Soldner mixer). Mixing clay in a slurry and drying out will produced a more thoroughly wetted and denser clay body  but it is much more work. If you are mixing in a Soldner style mixer there will be a lot of tiny air pockets in your clay. I have not read this anywhere but I have noticed it from my own experience...maybe others can confirm or deny. Either way, a vacuum de-airing pugmill will produce the densest and most homogenous clay body.  
  6. Like
    tinbucket got a reaction from Grace london in Interesting additions to clear glaze   
    2-3% lithium carbonate, pearl ash, soda ash, or borax can flux the glaze more (increase melting) and may improve the color response. If you don't seive the glaze after you add the material (just blend well) then you will be left with some crystals which will create some localized fluxing. I would not recommend any of this if you were making functional pots. I understand calculating percentage may be a little complicated since you are starting with a wet glaze. You can either add x dry to a cup of glaze, test, then adjust or calculate the amount of dry material in x amount of wet glaze by measuring the specific gravity.
    If you look at recipes for texture/sculpture/special effects glazes you will notice trends in the materials used and amounts. This will give you a starting point if you are looking for a particular effect.
  7. Like
    tinbucket got a reaction from Rae Reich in Porcelain Warping   
    Another thing to consider is the clay memory. Porcelain remembers. Say you remove a leatherhard pot from the mold and put too much weight on one side of it (imagine holding a cup sideways). Even if the pot does not go oval in that moment it may be enough for it to cause warping later on. However I suspect this is a problem with uneven drying, even a little bit can cause significant distortion
  8. Like
    tinbucket got a reaction from Bill Kielb in Make a shiny glaze Matt.   
    Can you give us some more information? Cone? Color? Recipe? Here are some ways to make a glaze matte: Increase alumina, decrease silica, add calcium, add magnesium 
  9. Like
    tinbucket got a reaction from Rae Reich in Terra Sigillata Flaking Off   
    @kathleencorcoran I have used Redart sig on bisque, then fired to cone 6 with no problems. This may be different with more refractory clays (ball clay/white sig). Sig is very opaque (I think because of the fine particle size) so you do not need a lot to cover the clay body. You can experiment with different thicknesses but I would try to use it the same way you would on greenware. Since you are pit firing the sig may adhere better to bone dry clay
  10. Like
    tinbucket got a reaction from HarryGateaux in Toasted clay on unglazed side of rim   
    As Neil and Magnolia said, I believe it is either volatile or soluble fluxes. Some glazes do this more than others but especially those with higher amounts of Neph Sy, Lithium Carbonate, basically any on the alkaline fluxes/feldspars high in sodium, potassium, and lithium.
  11. Like
    tinbucket got a reaction from Rae Reich in Porcelain vs White Stoneware   
    Glazes will look a little brighter and the body will be more white and glassy using porcelain. These are generalizations and it depends, of course, on the formulation of the body. If you are comparing white stoneware vs porcelain in reduction, transparent glazes will look far better on porcelain. Porcelain is generally less plastic and more thixotropic/more difficult to work with.  It's a trade off, workability for whiteness/translucency of the body and brightness of the glazes. I say make some of your work with 25-50 pounds of porcelain, 2 different clay bodies if possible, glaze it, and then assess the results. The only way you will know is to try it. There are many nice white stonewares out there but in my opinion porcelain has something that stoneware does not. Many times the compromise of workability is not sensible but it really depends on the type of work you are making and the glazes you use. 
  12. Like
    tinbucket got a reaction from colekeller in Porcelain Warping   
    Are your pieces warping in drying or firing? Evenly drying will take care of most drying warpage, I think. If your porcelain has a high amount of plasticizer this can require more attention. If your work is warping during the firing >>> Do you mix your own casting slip?  How important is translucency to your work?  Although changing the form will help I think the pyroplasticity of the porcelain is a more important factor. I think many porcelains are over fluxed to make them more translucent (a broad statement). For example you may be able to reduce the amount of feldspar in your casting slip, maintain 0% porosity, and reduce the pyroplastic deformation of your pots. Another option is adding a filler such as pyrophyllite or alumina. From what I have read potassium feldspars create a more viscous melt than sodium feldspars (custer will deform less than minspar in an equal level of vitrification). If you test/mix your own casting slip you will have much more control over the warpage of your pieces and have to compromise the design of the form less. I'm in over my head, calling on @glazenerd
  13. Like
    tinbucket got a reaction from VladCruceanu in Irregular shape pot   
    I would also suggest starting solid and carving away. If you want an angular form like that use a cut off wire or straight edged trimming tool to slice away. You can go at the block of clay with pretty much anything but I think it will be easier if you have some variation of the form in mind before you start cutting. Also! Look at Tim Rowan's work
  14. Like
    tinbucket got a reaction from Mullins Pottery in Making a cone 04 clay go to cone 10   
    Not only try "cutting it" with a high temperature clay, do a line blend! At least 20/80, 50/50, and 80/20. Absorption/shrinkage bars should give you some idea of what's going on. Also, I'm assuming you are firing cone 10 reduction, and cone reduction will effect the fluxing action of iron more than oxidation will, I'm sure others can give a better explanation of this - my understanding iron in reduction = more melty/stronger fluxing
  15. Like
    tinbucket got a reaction from Rae Reich in How to fix warped plates   
    If you use a slab roller and only roll the slab one direction, it can create uneven tension on the clay, and cause to shrink more in that direction. You may benefit by rolling the slab to the partial thickness, rotating the slab 90 degrees, then rolling to the finished thickness. You may also benefit from flipping the slab over. Another thing I have seen people do with slab plates is weigh them down while they are drying - a sand bag of sorts in the center of the plates. I think any combination of these techniques is worth trying. Some clays have a very sensitivd memory as others have mentioned and it is best to be aware of this when handling the clay - leatherhard pieces
  16. Like
    tinbucket reacted to GEP in Mug handles cracking at joint.   
    I wet pull handles from leatherhard mugs, which means the handles are much soggier than the mugs. After I handleize a run of mugs, I cover them with plastic. In about 24 hours, the moisture will have equalized throughout the pot, and they can be uncovered to finish drying safely. 
  17. Like
    tinbucket got a reaction from LeeU in Glaze firing for spoons and other flatware   
    Fireclay will be slightly more refractory and have greater thermal shock resistance, they might last a little longer. If you don't have fire clay you could make it out of your usual stoneware. Build them sturdy and they should work. If I spent a long time on a single spoon I would be inclined to test my racks with some weight on them before firing a glazed spoon. Up to you. Maybe others can chime in. I have never done this, I just got the idea when you posted your question. If your spoons are light you could try them on a premade bead rack, but I would be weary of putting anything heavier than beads on a bead rack
  18. Like
    tinbucket got a reaction from Rae Reich in Glaze firing for spoons and other flatware   
    The are called insulating fire brick (IFB) or soft brick. They are much less dense and therefore absorb less heat than typical hard brick (good if you want fast temp rise/fast cooling/less energy use and not good if you need to retain heat or cool slowly). Almost all electric kilns are made from insulating fire brick.
    My suggestion for the spoons would be to buy some thick high temp wire and build your own "spoon hanger" out of Hawthorne or similar fireclay. Make it so that each spoon hangs with support on each side from an unglazed hole on the spoon handle. By making your own you will maximize the efficiency of firing/stacking space and ensure that the spoons are not all hanging together on a long span of wire.
  19. Like
    tinbucket got a reaction from Duende in Glaze firing for spoons and other flatware   
    Fireclay will be slightly more refractory and have greater thermal shock resistance, they might last a little longer. If you don't have fire clay you could make it out of your usual stoneware. Build them sturdy and they should work. If I spent a long time on a single spoon I would be inclined to test my racks with some weight on them before firing a glazed spoon. Up to you. Maybe others can chime in. I have never done this, I just got the idea when you posted your question. If your spoons are light you could try them on a premade bead rack, but I would be weary of putting anything heavier than beads on a bead rack
  20. Like
    tinbucket got a reaction from Duende in Glaze firing for spoons and other flatware   
    The are called insulating fire brick (IFB) or soft brick. They are much less dense and therefore absorb less heat than typical hard brick (good if you want fast temp rise/fast cooling/less energy use and not good if you need to retain heat or cool slowly). Almost all electric kilns are made from insulating fire brick.
    My suggestion for the spoons would be to buy some thick high temp wire and build your own "spoon hanger" out of Hawthorne or similar fireclay. Make it so that each spoon hangs with support on each side from an unglazed hole on the spoon handle. By making your own you will maximize the efficiency of firing/stacking space and ensure that the spoons are not all hanging together on a long span of wire.
  21. Like
    tinbucket got a reaction from Magnolia Mud Research in terra sig vs. slip   
    I asked my friend a very similar question recently and she prefers terra sig because it is like the pot is wearing a thin veil versus slip which is like a the pot is wearing a thick winter jacket. Covering a pot with slip removes some of the marks made by the maker's hand. I have been experimenting with terra sig and although I know it is not the traditional use, I have been very happy with Redart sig at cone 6. It doesn't completely melt and is not 100% water tight, but on the outside of a pot is a beautiful deep red with a slight shine. 
  22. Like
    tinbucket reacted to Mark C. in Measuring pot bottoms   
    I feel its better to lean how to do this with ones hands by learning how to feel the pot and it thickness. Its a skill set and potters need to learn it.
  23. Like
    tinbucket reacted to Mark C. in Measuring pot bottoms   
    If you trim a lot eventually you can feel the thickness without any thing but your fingers. I pick up a bowl that needs trimming and feel it then trim it.After doing this for years it only takes once but while you are learning you may have to handle it several times.
  24. Like
    tinbucket got a reaction from Jeremy Ayers in c6 glaze too soft   
    In the first recipe, the zircopax may be the cause of the cutlery marking. Search zircopax on digitalfire.com and you will see more info on this. I would try a line blend of the glaze, reducing the zircopax to see how much is necessary to opacifiy your glaze. Then I would add silica in 5% increments to see how much the glaze could take before adverse effects arise. Also the first recipe that Min posted is a glaze I am testing right now. The matte surface of that glaze has an opacifying effect on its own, requiring less tin or zircopax to achieve the same opacity of your current white.
  25. Like
    tinbucket got a reaction from claclana in Ceramic Tape Recipe? (Like Keraflex)   
    http://www.alfredgrindingroom.com/raw-materials/
    http://www.alfredgrindingroom.com/recipes/
    ^ A wealth of information on ceramic materials and experiments. The tape casting pdf is on the first link, the same one posted by two others in this thread
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