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Magnolia Mud Research

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    ceramic chemistry

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  1. Magnolia Mud Research

    Glazing on already glazed tiles

    Paul Lewing recently posed to Clayart that he has "partnered with an online art school to bring my china painting workshop to more people. This is a new school, owned by Antoinette and Koos Badenhorst, out of Saltillo, Mississippi, called TeachinArt. This is a 6-week video class with demonstrations, assignments and critiques. It's as close to what I do in my in-person workshops as we could make it, and I'm very pleased with it. The first class will start in mid-September and pre-registration is open now. Go to http://teachinart.com/index.html " LT
  2. Magnolia Mud Research

    How to do Acrylic paint style pouring in ^6 glaze

    Larry, Try using acrylic matte medium as a carrier for your glaze ingredients. LT
  3. Magnolia Mud Research

    Hudson River Clay

    When I decided to try using my pond clay, I made a series of small pyramids, aka cones, scaled after regular Orton cones. I placed these 'test' cones in a holder big enough to catch all the mess if the clay fully melted. I also placed a pack of regular cones nearby so that I could have a good comparison of my clay with the cones. As I remember I used the regular cone back we used for the school's cone 10 firing - cone 06, cone 3, 5, 9, 10, & 11. My clay was not mature at cone 10, it was more like bisque ware. A recent test of some "unknown" tramp clay was tested to see what happens, done the same way, The clay fully melted at cone 10 and would be useful as a glaze. LT
  4. Magnolia Mud Research

    COE and Thickness

    Then why does thick homogenous glass (or for that matter cast iron) crack when heated too fast or cooled too fast? Me thinks that "shouldn't have crazing issues at any thickness" is an overly optimistic generalization. Again, cracks develop because of excessive local stress. "Why are these stress occurring where they are?" is a better problem question. Until you have identified ALL the variables, you will not understand the reasons for the excessive stresses. Min's experiment show that thicknesses of the glaze drops are in her test pieces is not a significant variable; HOWEVER, is Min's test representative of the glaze and application situation of Neil's forms? Is the glaze strength in the test glaze similar to the glaze in the cracked glaze (Neil's glaze); are the test tiles representative of Neil's forms, ...? My point is that while tweaking Neil's glaze for his application is likely to be successful, our collective understanding of glaze crazing is still in the trial and error stage for most situations because we, as potters, have not yet explicitly acknowledged all the relevant variables. Neil's crazing situation is a good candidate for the Root Cause Analysis technique Chris Campbell asked about back in March. RCA starts with the failure; crazing where not expected based on prior experience. Questions that might provide insight include, where does this failure occur? Where does this failure NOT occur? Does this failure occur on all clay bodies or only on one clay body? Does the failure occur on all forms or just some forms? Where in the kiln were the forms placed for each item? What are the specific differences between the areas, forms, and clay bodies where the failure occurs and where the failure does NOT occur? What is the measured COE of the glaze; the estimated (from the glaze calculation software) COE of the glaze; what is the COE of the clay body; How thick was the body where the failure occurred and how thick was the body where the failure did NOT occur ... And oh yes, do not forget the question "why does ceramic objects and glaze crack instead of just thinning like a thread of polythene?" Answers should be specific, such the failure occurs only on shoulders; the failure NEVER occurs near a lip nor on the inside of the form; the object with failures were never on the top shelf; .... Yes, there is a probability of being on "a ride down the rabbit hole;" been there many times; however, after reflection the trip always lead to greater insights into both the specific problems and greater insights into the task of problem solving. LT
  5. Magnolia Mud Research

    Well, There's Your Problem!

    I use a commercial low-fire white clay body described as: "A smooth clay that fires a nice snow white color. Suitable for hand-building or wheel-throwing. For the best results, bisque to Cone 04 then glaze to Cone 06". my protocol is: bisque to ~cone 07; fire at Cone 3 oxidation for dinnerware; and use as a stiff matte white/gray glaze at cone 10 oxidation/reduction. The red version works the almost the same way; the difference is that at cone 10 reduction the glaze is red/black and moves but is not truly a "runny glaze". LT
  6. Magnolia Mud Research

    Engobe question

    Having learned the hard way, when I have multiple options, such as the ones you have mentioned, I plan to test each way and do a careful evaluation of the outcomes to see if the final results are justified by the 'extra' efforts of each pathway. My experience has been that such a protocol provides more information about outcomes; and that 'extra' information will be useful in later situations. That said, I have found that application of commercial coatings such as engobes and underglazes prior to a bisque fire results in better adherence of the coating to the substrate. If I am applying decorative underglaze to bisque ware the ware is bisqued (again ) prior applying glazes. LT
  7. Magnolia Mud Research

    Flat Brushable ^6 + glaze

    My limited experience with painting in ceramics class: 1. I was amazed some years back when an artist came by with a painting made on a bone dry clay plaque. He wanted to know if he could fire the plaque in our cone 10 gas kiln. No one really knew what the outcome would be, but our expectations were pretty low. The fired plaque painting lost a lot of its brightness; and colors were generally different after the firing than before. I don't remember if the paint was oil, water color, or acrylic. However, the 'success' of his plaque inspired (on my part) a series of tests using various media normally used on paper and canvas but applied on bisque ware of various clay bodies. My tests included oil pastels, oil paints, water color paint, acrylic paint, and school wax crayons. Many burned off completely because the pigments were organic dyes; the paints using pigments containing transition elements always produced some coloration. I also learned that there are standardized pigment codes for artist paints that are "decoder rings" for transforming the ingredients in the paint to the elemental information needed to determine if the pigments will have a residual effect after firing. Such a list shortens the number of tests. I no longer have a copy of the 'decoder ring.' With careful documentation it should be possible to match a fired color to the coating applied before firing; I did not go down that 'rabbit hole'. 2. I have used the AMACO Semi-Moist Underglaze pans (I consider them to be ceramic watercolors) to make paintings on ceramic ware. They act just like watercolor painting on very dry thick watercolor paper. The fired results are a dry image. If a very thinly sprayed coat of low fire clear, or just a thin spray of baking soda solution, will add some gloss without making the surface appear "glossy" or "glazed". 3. If you are firing at mid-range or lower, you can coat the regions of the pot to be "painted" with a slip of a cone-10+ clay body ( I use cone 10 porcelain for a white surface) to produce a semi-porous dry canvas (after the 'glaze firing') on which you can actually paint real watercolor or oil paintings [mixed-media work]. 4. A colleague a few years ago conducted a limited test set of blends of AMACO liquid underglazes with our studio cone 10 clear glaze. I don't remember the details (I was not really interested in the test) other than the experiment was somewhat successful; the test was definitely not a disaster. LT
  8. Magnolia Mud Research

    COE and Thickness

    Neil, My thoughts: My guess is that the 10% failures may be crazing due to being cooled too fast. Surface crazing is due to stresses in the surface layers that exceed the strength of the surface material. Beside the COE differences between the glaze and the clay body, there are a differences is the thermal conductivity and of the specific heat of the glaze and the clay body. Slowing down the cooling leads to smaller gradients in the surface temperatures and therefore lower stress gradients within the glaze layer. Try slowing the cooling cycle at the lower temperatures. Start by comparing your cooling profile with the cooling profiles needed for thick walled glass work. I have colleagues working with glass and if they cool (or heat) the glass too fast, their work gets surface cracks that propagate through the work. Bullseye Glass in Portland, Oregon is the technical data source used by my colleagues working with fused glass. They have lots of info on glass cooling cycles. LT
  9. Magnolia Mud Research

    low fire reduction shino glaze recipe

    You could try adding more of the high sodium ingredient(s) (such as the feldspar or nephsy) in your current recipe; or just add a high sodium feldspar or frit to the same recipe. LT
  10. Magnolia Mud Research

    Creating texture with airbrush or gun

    I surmise from your comment re Ron Nagle's work that you are trying to produce visual texture as compared to physical tactile texture. Think "splatter painting". Try spraying with a screen mesh between the spray tip and the work. Vary the screen mess size and the separation distances between the spray gun, the screen, and the ware surface. That should give you very wide range of effects. Also the viscosity, surface tension, and density (aka solids to liquid ratio) of the glaze slurry are variables in the size of the droplets that reach the ware surface. LT
  11. Magnolia Mud Research

    Low-Fired (Cone 04) Porcelain Characteristics

    Soren, Take the white clay body you have and conduct a set of firings from say cone 05 to cone 3 or to the max temperature you kiln will reliably (meaning repeatedly hit the target). evaluate the porosity, color, strength, etc. Then, on the basis of your experiments, choose the set of conditions that produces the best product. Also keep in mind that you can bisque to a higher temperature and the glaze fire at a lower temperature. For instance take a cone 10 porcelain bisque it to cone 5 and then add stains glaze, slips, engobes, etc. and fire to cone 04. There is no rational reason for you to follow the herd to the firing sequence, (or raw materials), or some target that does not produce the product you want to make. You know the characteristics you want in your product. Keep tweaking the materials and the processing schemes to achieve your goal. I learned long ago, that I can take control and adjust the system to use the materials and equipment I have to do the job; most of my work has been breaking the rules to achieve success. In other words, use your engineering background to guide your ceramics creativity. LT (Ja, Ik ben een ingenieur!)
  12. Magnolia Mud Research

    Staining Amaco versa clay #20 Body

    This clay body, Amaco Versa Clay No. 20, appears to be similar to a low fire clay I used when I was first introduced to ceramics. The clay I used (Armadillo Long Horn White) is a talc based clay body that is grey in the bag, and fires to a very bright white at temperatures above cone 08 (which is our bisque temperature at school). I fired it at cone 3 in an oxidation gas kiln and it responds well to cobalt , copper, and iron glazes at cone 3. I also used it for raku and it produces good colors there. I also use this clay as a slip glaze for the exterior of bowls made with dark firing clays at cone 10. My comparison with porcelains is that it is a brighter white fired at bisque and at cone 3 than the popular porcelains fired to cone 6 and cone 10 reduction.
  13. Magnolia Mud Research

    orton numbering

    call Orton, their phone number and other contact info at: https://www.ortonceramic.com/ LT
  14. Magnolia Mud Research

    STPP Alternate

    soda ash will work, cheaper than tsp (sometimes).
  15. Magnolia Mud Research

    Sculpting with 2 different clay bodies, can it be done?

    Based on your statement of two cone 6 clay bodies each with 13% shrinkage and joined with slip made from equal amounts of both clay bodies, I would not have any more concern with the project than one using a single clay body. I often join different clay bodies with the technique you described, including porcelain to stoneware with large iron content. Test the strength of your joining techniques on ware other than your final sculpture to be sure both the clay body and the joining techniques will be reliable. For some of my multi-clay body projects, I used a gradient of both clay bodies over a centimeter or more to mitigate the known differences in the shrinkage rates. .. My recommendation is to thoroughly think through the sculpture from a structural point of view and if possible use one clay body for the load bearing and supporting components. Where the sculpture will have high stress points, make test pieces to be sure that the clay body joins will be adequate. LT

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