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Magnolia Mud Research

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Everything posted by Magnolia Mud Research

  1. Magnolia Mud Research

    cracked bisque -- will it break with ^5 firing?

    Incorporate the crack into the design of the sculpture and move on with the piece. when making your next piece, maybe a reengineered version of the one that cracked, improve the construction to avoid the stress concentration in the area. LT
  2. Magnolia Mud Research

    Sculptural questions/bad ideas

    I have used several different low-fire commercial clay bodies for decorative surface effects on work fired to cone 10 reduction in a gas kiln. Each clay body reacts differently; some expand and others don't. I also use raw wild clay from my ponds and uprooted trees, again each source has different effects. My advice is to set down and make of list of the materials you think would be available for use, then obtain about a liter of each, and make tests. First place a spoon full of each material into a bisqued test cup and fire the sample to your final temperature with your typical firing schedule. Carefully observe the outcome of the firing. Then wedge some into your favorite clay body and repeat the test. A question only you can answer: Are you trying to create ware that has the appearance of having been 'expanded' or must the ware actually 'expand' when fired? I have seen ware that appeared to have been expanded (holes and cracks that appear to be stretch marks) but actually were created by having material 'burn out' of the clay leaving open spaces. I have placed paper between the edges of stacked slabs to create the effects of surface cracks. Also used rice grains to create porous surfaces. As a kid I played with a vermiculite which expanded when heated. Don't know if that material is still available since it was used then as a packing material similar to today's Styrofoam peanuts. Your ideas are limited only by your willingness to try it. LT
  3. Magnolia Mud Research

    Calcined Zinc Oxide

    I am sure that this discussion is about zinc oxide and not zinc! There is a big difference. (Nomenclature is important). Also zinc oxide will absorb moisture if left open to the ambient atmosphere ( except maybe in the Death Valley desert); the recipe should be adjusted to compensate for the added moisture
  4. Magnolia Mud Research

    Firing and cooling kiln

    Iron can migrate if the kiln atmosphere contains HCl or salt because all metal chlorides have non-trival vapor pressures at kiln temperatures. Salt kiln would be an example where iron might move around. Since chlorides are not a standard ingredient, in normal clay bodies, glazes, or electric kilns, I agree with Neil — except where halide elements are present. LT
  5. Magnolia Mud Research

    Clumpy glaze

    I have been working on a cone 10 matte base glaze. Your recipe is similar to our clear glaze base with dolomite and extra EPK added and without the borate. Thanks for the recipe and test piece images; these data have provided me with a different direction to explore. Suggestion for troubleshooting: Separate the 'globs' from the glaze, and fire them separately on a test piece. also let the 'globs' dry and compare to the glaze ingredients. LT
  6. Magnolia Mud Research

    Spectrum glazes didn't fire correctly

    If your testing shows that the kiln will not reliability achieve cone 6, I suggest that you lower your target just a little and fire the available low fire clay bodies to cone 3. When I first started, the college studio fired a low fire commercial clay body to cone 3 oxidation. All the ware was at zero water absorption and the studio glazes were fine. There were also some engobes used that widened the glaze palette. Glaze layering was also an effective technique along with commercial underglazes. There was never any issue of the low fire clay body having excessive slumping, bloating, etc. due to over firing even though the clay was designed for cone 04 bisque and glost firing at cone 06. (I currently use that clay body as a cone 10 dry matte glaze). The clay body was chosen by his testing the available clay supply options. LT
  7. Magnolia Mud Research

    piping slip

    Key question: Is the “cake” to be fired? If not, lots of options are available; if “cake “ is to be fired, stay with ceramic based materials as Mark recommended. LT
  8. Magnolia Mud Research

    removing e6000?

    Since the adhesive is rated only for temperatures less than 82 C, boil the frog until he turns loose.
  9. Magnolia Mud Research

    Suspending grog in a slip

    Yes, I compress the paste into the body with the pallete knife as it is applied. Brushing usually works ok for the slip, but the 'big chunks' sometimes fall out if the applied layer is too thin. My 'chunks' range in side from less than half a millimeter to five millimeters; it is the larger ones that are more likely to have adherence problems if not compressed, especially if the applied layer is thinner than the 'chunk'. Make small test forms to try out variations of the technique; pay attention to what you do and what actually happens at the wet, drying, and final steps. When I have used thin slips without big chunks, no problems with pouring or brushing application. Have not tried dipping.
  10. Magnolia Mud Research

    Suspending grog in a slip

    I add “chunks” of wild raw clays, crushed bisque shreds, and/or small rocks to porcelain at a consistency of toothpaste. Application is with a pallete knife or stiff brush. I mix the paste as I need it using bagged porcelain, water, and “chunks” to get the thickness needed for the project; the leftovers are stored in a closed container as a starter for next project. Compression of the paste onto the substrate has been the key for success in my work. Shrinkage cracks are assumed to occur and are considered part of the design.
  11. Magnolia Mud Research

    Electric Reduction Firing

    About 10-15 years back (+/-), there were Clayart discussions on reduction in electric kilns. Mel Jacobson discussed his conversion of a small electric kiln to fire in reduction; Lee Love and John Baymore both discussed how the Japanese were routinely using large electric kilns for reduction. From what I remember from these discussions the customer base for electric reduction kilns is unwilling pay the cost of a well designed electric kiln for controlled reduction. As a point of comparison, the heat treatment industry routinely uses electric furnaces for controlled atmosphere treatments of various metals where the atmosphere is in what a potter calls 'reduction'. LT
  12. Magnolia Mud Research

    Hardening of glaze

    I suspect that “crystal “ formation is just a term being used to say that the glaze slurry settled to a hard lump, aka “hardpanned”. LT
  13. Magnolia Mud Research

    How it's made

    Why not use the 3-D printer to make the mould(s)? LT
  14. Magnolia Mud Research

    Crystalline Glaze Chemstry

    Many solid-water slurries have a maximum volume percentage of about 60 percent solids. Based on that "rule of thumb" in the solid/water slurry engineering domain, and my experience with slurries both inside and outside of the studio potter discipline I use the following procedure: for glazes using clay, crushed rocks (feldspar, limestone, quartz, etc), crushed glass (aka frits), and colorants as major ingredients : I start with an amount of water that is 60 of the weight of the solids and additives being used. In other words if the solids is 1000 grams total, I use 600 grams of water. If the slurry is too stiff, I will carefully add additional water to meet the consistency needed for the application. When the glaze has been tested and declared successful, the amount of water as a percent of the dry solids is added to the recipe. I have not needed more than 70 % wt. water for the glazes I use. Most of my glaze application is dipping or pouring. More water may be needed for spraying. The procedure works for me . LT
  15. Magnolia Mud Research

    Adding handle to cup

    I have had success attaching two bone dry pieces together with moist paper clay paste made by adding vinegar to paper pulp and the same clay body as the parts being joined. The steps I follow are: "spot wet" the joining area (I use a brush to apply the water) when the shine of the added moisture is about to disappear, add the paper clay paste to both pieces and compress and clean up the joint. position the pieces so that gravity is works in your favor, not against you. My success rate has been about 4 out of 5 so there must also be the unknown factor related to what I had for breakfast three weeks prior to the joining attempt . If I were to try to add a handle, I would make the handle, let it dry to the point where the handle no longer shrinks and then attach the handle. the success will depend on the design of the cup and handle plus the shrinkage stresses that develop after the joint has been made. I have never had success attaching a wet handle to a piece of bone dry clay -- with the exception of all the parts being paper clay. LT
  16. Magnolia Mud Research

    How it's made

    Or produced in a press mold. LT
  17. Magnolia Mud Research

    Crawling matte glaze. Any hope of saving these?

    "Matte-ness" is an optical characteristic of a surface, not necessarily a chemical one. That said, the elemental composition and thermal history strongly effect the optical properties of the glassy melt that we potters call 'glaze'. (The article on to Ceramics Art Network Daily "What Makes a Matte Glaze Matte?" has good images illustrating the optical difference between glossy and matte surfaces). This discussion has been informative - at least to me - because: 1. The topic is currently relevant to my current assignment to develop a reliable cone 10R matte glaze using a constrained array of potential ingredients; 2. The discussion highlights the confusing usage of words in the realm of ceramic art/pottery to explain specific aspects of physical chemistry and mechanical physics where words have specific meanings in the disciplines. Too often a word commonly tossed around within one disciple will mean something significantly different within another discipline or the word is used to convey multiple meanings. I have encountered the situation numerous times since I entered the ceramic art discipline. example: a discussion about "thickness" of glazes: is the discussion about the solids/liquid ratio of the slurry, the fluidity of the slurry, the amount of dried unfired material per square meter of pot surface, or the thickness of the fired glassy surfaced formed on the pot? the solution of a problem will be different depending on which meaning you assume for "thickness"). Stull's empirical analysis of the silica-alumina molecular ratio in common alkali/lime glasses is an important data set (Trans. ACerS vol. 14, 1912), so is the discussion of matte/gloss glaze in Parmelee and Harman (Ceramics Glazes, 3ed.,1973). After reading Stull and Parmelee, and examining a few geochemistry phase diagrams, I am convinced that the mattness of the Stull glazes is most likely due to the precipitation of calcium aluminosilicate (aka calcium feldspar) from the melt created buy the ratios of the ingredients in the glaze and is not likely to be significantly different on fast or slow cooling as used today. There are post firing treatments that can convert a mature glossy glaze surface into a mature matte glaze surface - sand blasting and chemical etching are two processes that quickly come to mind. Also a matte surface can be polished into a glossy surface with rouge and diamond dust. I converted a glossy clear glaze to a white matte glaze by adding 20+ %w Zircopax to the batch (which was definitely an underfired glaze since Zircopax at that level is not soluble in the melt at cone 10). The white matte glaze is as stable as the clear glaze, no more, no less. An observation from both my own studies and my understanding of the discussion so far: The mattness depends on the surface having a preponderance of crystalline (Parmelee's term) species as part of the surface. This implies that the surface does not consist of the same species distribution as the bulk melt from which the crystals were precipitated. This leads to the conclusion that mattness may produce significant changes in the leaching of elements from the final glaze surface. Some glazes recipes can be forced into forming crystals on the surface by slowing the cooling rate, and some are likely to not form crystals within a reasonable time frame. Stull's chart is a reasonable starting point for alkaline/lime melts (without colorants) for a cone 11 firing. Now, back to the original question of the "crawling" aspect of original post. Is it the consensus that the crawling observed is an application issue (and/or the solids/water ratio in the slurry) and therefore is not specifically related of the glaze used on the pot being a matte glaze? Respectively, LT
  18. Magnolia Mud Research

    Lucy Rei Glazes?

    Roger that. Thanks.
  19. Magnolia Mud Research

    Lucy Rei Glazes?

    Terri I think you can find it in this book: Modern pots : Hans Coper, Lucie Rie & their contemporaries : the Lisa Sainsbury Collection Hans Coper, Lucie Rie & their contemporaries Hans Coper, Lucie Rie and their contemporaries Lisa Sainsbury Collection Author: Frankel, Cyril ISBN: 9780500975954 9780946009367 Publication Information: Norwich : University of East Anglia ; Wappingers Falls, NY : Distributed in the U.S. and Canada by Antique Collectors' Club, ©2000. I will not have access to the library until Tuesday afternoon to look it up. here is a recipe that I have used on 'stuff' for raku, cone 3 oxidation, cone 5 reduction/oxidation, and at cone 10 reduction. It is close to Lucie's concoction published in the book. the 'goldness' is related to thickness and it runs when thick. For me it worked best (gold forming) on white bodies and porcelain. I have worked with it applied at green ware states and bisque state. also have applied over and under other glazes (but don't remember the outcomes other not total disasters). The recipe is just a starting point. tweak everything to fit your clay body and firing conditions. I think the color depends on the elemental ratio of copper and manganese. During my playing with this line of decoration I also applied copper carbonate and manganese dioxide separately as suspensions in water (with some detergent to adjust surface attention) over the "bronze glaze" mixture. ∆3 Bronze . grams .Manganese dioxide 60 .Cu carbonate 10 .Red Clay - I used Redart 20 .EPK 10 .total 100 grams LT
  20. Magnolia Mud Research

    firing round ornaments

    I fire fully glazed items to cone 10 reduction setting on sea shells filled with wadding or just regular clay. The top of the shell is in contact with the glaze - the clay/wadding is just to support the shell when it gets hot. for spheres I would use three per sphere. Others at school have fired glazed items setting on a bed of crushed oyster shells (obtainable at a farm feed store). Either route will leave a small scar on the glazed item, but that can be polished with a good grinding pad or a sharpening stone. The shells calcine to calcium oxide (which with the help of soaking in water washes off easily.
  21. Magnolia Mud Research

    Triple beam or digital scale?

    I prefer the triple beam for the following reasons: I do no need to make glaze batches that require more than ~3 kilos of any ingredient. which means that I can always get to the necessary amounts in one weighing for each ingredient. The precision of the triple beam is adequate for all the batches I need, even for cobalt (which often needs ~half gram amounts) for 100 gram test batches. Triple beams are easy to maintain. Always works and never needs a fresh battery or an electrical outlet. Both triple beams and digital scales need to sit on a level platform for reliable data output. The triple beams are very easy to calibrate, digitals are not, my experience is that those using digitals do not know how to calibrate the scale, and therefore fail to do so. Calibration of measuring instruments is essential for both glaze making and kiln firing. The biggest issue I have observed over the last decade is that most folks do not know how to use a scale that requires the operator to deal with the 'tare' weight of the container of the materials being measured on the scale. A good digital will have such a button for that, but even the tare feature must also be calibrated at regular intervals. Mark, a full time production potter, handles large quantities of materials on a frequent production cycle. A hobby or part-time potter handles small quantities on a less frequent schedule. Both weighing contraptions are adequate if well maintained. The final decision is really a personal decision, for your situation. LT
  22. Magnolia Mud Research

    first craft fair WWYD?

    Tony's "crack" is a special version of a shino glaze that develops cracks in the raw glaze surface before the ware is fired to maturity.
  23. Magnolia Mud Research

    first craft fair WWYD?

    Have a look at Tony Clennell's birdhouses: http://smokieclennell.blogspot.com/2018/09/one-flew-over-cuckoos-nest.html
  24. Magnolia Mud Research

    Metallic lustres

    Acrylic paint is a water emulsion of poly-acrylates which contains only elements carbon, hydrogen, and oxygen. Clean combustion of the acrylate produces carbon dioxide and water. Use same good sense as you would with using paper clay, wax, CMC, glaze resists, etc. As my grand pappy used to say, “always stand up wind of the fire”.
  25. Magnolia Mud Research

    Metallic lustres

    Rae, Several years back I conducted some experiments using acrylic paints (mostly artist paints and white and black house paints) as a source of color in cone 10 reduction firing. A few semesters ago I repeated part of that experimental protocol on fused glass work. If the pigments in the acrylic paint are based on metal such as copper, iron, chrome, cobalt, etc. the residue after the organic medium burn off the residue will contribute to some color. The intensity of the color will depend on the pigment and its loading in the medium, and the specific metal specie that remains in the surface layer of the fired object. Many of the common artist acrylic pigments are now all organic species and will burn off. The ingredients in the paints are listed on the container, often in pigment jargon of pigment numbers. There are several websites that have decoder rings to translate from pigment code numbers to specific chemical identities. No, I do not have urls. After the experiments I only now use cobalt and black iron acrylic paints in my ceramic work, and then only as an accent effect on raw clay surfaces. Without the specifics of the pigments, just try a bit of acrylic, or other painting medium on a test piece and see what happens. The worst that can happen is that you become addicted to the technique. LT

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