Magnolia Mud Research

When we produce a ceramic material that allows "light" to pass through that material we are working with a "glass" even though us potters call the material a clay body or a glaze. Todays "Ceramic-Tech-Today" article: Colored glass: From alchemy to empirical chemical design https://ceramics.org/ceramic-tech-today/education/colored-glass-from-alchemy-to-empirical-chemical-design/ has some useful information and background that might help determining why the bone-china pots show a color when seen in a light source. Remember that the source of the "light" is also an important variable. LT

you will often get a greenish shine from a light on window glass at an angle. small amounts of iron in the glass is mostly the reason, but the source of the light and thickness of the glass are also a variables. take a look at: https://physics.stackexchange.com/questions/247939/why-is-glass-green question: When I look at a glass block at an angle the edges appear green, but when I look at the edge sideways, so that is directly in front of my eyes it appears transparent. Why? answer: Most glass contains iron oxide as an impurity which gives the glass a slightly green hue. When you're looking straight through a pane of glass you don't notice it because the glass is so thin. But when you look down the side it becomes apparent because of the thickness. LT

I've been there. and learned to ignore the "official methods" and simply crushed the dry clay as small as possible using a hammer and kitchen screen utensils to get rid of the "big" rocks. Mix the clay with water to make a slurry that is somewhere between the buttermilk and the milk level (or a little less). Let the mixture set for a while to let the heavy particles to sink, and then pour the liquid into a separate container which will contain most of the sig. Stir up the original container again and let it set a while, and repeat pouring off the water to get remaining sig. Yes, this is not the official method, but it has worked just fine for the clay I take from my ponds and roads to them. I have also used that same method for making sig from scrap commerical clay bodies. If you are able to get wet clay from the backyard just start with that; add water and mix well; if you have sand, it will sink along with the heavy particles. I have a pond that collects fine clay every time there is a decent rain. After the rain there will be a thin layer of fine clay above the big paricles. My first round on terra-sigillata I followed the "official" method; it worked ok. After noting what was happening in the ponds and just getting a bucket of pond mud and water I begin to make my own method which has worked just as good as the textbook. The best "official" recipe I have found (beyond my own) is Vince Pitelka's version: http://www.vincepitelka.com/wp-content/uploads/2022/10/Super-Refined-Terra-Sig.pdf /*/

when wondering around the property this week I notice a rotting stomp of a large pine tree that was blown down a few years ago; the dried yellow clay still on the bottom of the stomp was simular to the color of the plastic cat litter buckets; the clay on the stump contains iron oxides. Long ago while solving problems for plastics, fine particles of iron oxides were used to produce colors to the plastics. My point is you should think about the iron being taken from the plastic. Test using a plastic bucket that is not yellow. LT

I have been down a similar route long ago: make a round object (a piece of stiff flat tarpaper); place on the soft clay; use a sharp cutting tool (I used a small sharp pointed kitchen knife) to cut the circle of clay. Start with a large flat sheet of clay on a piece of dry paper or cardboard, use the round object and the knife to cut the clay with the knife; when all of the coasters are cut, then remove the clay between the coasters leaving the coasters on the cardboard. The coasters are allowed to flat all the time. smoothed the sharp edges of the coaster after the bisque. LT

To get a "blue" shino: Take your own plain shino glaze recipe. Add a "pinch" of cobalt to that glaze; make a test to see if you like the "blue"; If not enough blue, add another "pinch" of cobalt; if to much blue, use "half a pinch" (this is just like finding how much sugar you need in you coffee). warning: too much cobalt will produce black blue (or a blue black). the images are for cone 10 reduction on a studio clay body. one is plain shino, the other is shino with cobalt (aka blue): LT

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I have done what you are doing. The application of the glaze is one of the main variables. The glaze composition and the "stiff ness" of the melted glaze is also an important variable. There will be a difference between raw clay ware joining and bisque ware joining. Both are possible; important variables: application of the glaze, porosity of the bisque surfaces, and the thickness of the glaze slurry. Always make sure that weights and gravity are working for you at all of the joints. the glazes used for my work was a shino glaze (very stiff) and a clear or celadon glaze (not very stiff); all cone 10 reduction. It works also at lower temperatures, just use glazes to fit the temperature. LT

Do you have a clear glaze that works OK all the time? if so, just add some Zircopax to your clear glaze and you will have a white glaze. the amount of Zircopax will probably be somewhere between 4 and 8 %. LT

I have created this texture by dipping the bowl in glaze, and immediately roll the bowl in a container of dry sand or crushed white dried claybody. The wet glaze will capture the dry material and "glue" the dry material to the surface during the firing. A similar effect using a slip of the bowl's claybody on the bowl surface followed by the dry material. My experience has been that the a "stiff" melted glaze works better than a runny one, but both will work if the ratios of glaze and dry material are worked out by testing. LT

I have been making exterior surface coatings of all form of items, bowls, vases, bottles, and sculpture using a paste (think toothpaste or soft butter) of various kaolins. The paste is applied to the clay body (prior to bisque) and compressed with a spatula; . I have also used dry kaolins, ball clays, and "wild clay" dust to rub into rough surfaces of bisqued (and bone dry surfaces) to change the color of the fired ware. I used paste and dry materials to avoid having to deal with extra moisture that a slip produces. my work is fired to cone 10+ reduction; some sculpture is only fired to bisque. LT

A good "BAT" discussion can be found at: How to Make Throwing Bats https://www.vincepitelka.com/wp-content/uploads/2019/02/How-to-Make-Throwing-Bats.pdf an alternate to hard bats try the flexible ones: https://www.vincepitelka.com/wp-content/uploads/2019/02/Throwing-on-Canvas-Bats-as-an-Alternative-to-Rigid-Bats.pdf I use both kinds depending on why, what, where, and when the "bat" is needed. LT

My mark tool started a square shaped piece of soft clay with a carved design on that piece; had it bisqued and start using the then hard stamp. I have made many over time; it took more time thinking about the "design" than it took to actually make the item. I now have different sizes for different sized objects. Just prior to sending all objects to the bisque firing, I also mark the bottom of the objects with an "iron oxide and water ink" applied with a fine tipped brush; the iron oxide mark has shown on all clay bodies from white porcelain to red clays for low temperature (cone 08) to cone 12 electric, gas, wood, and Raku firings; this homemade "ink" works better than any other material. LT

an alternate approach to remove "gloss": place the object in a container of sharp sand then vibrate the container for a few minutes; the sharp sand will create scratch the glaze surface and remove some the "gloss"; take the object out evaluate the "gloss"; repeat as needed. You can also use fine emery paper and change the "gloss". LT

my assumption is that you are looking for the amount of sodium in the slip. the amount of sodium in: sodium bicarbonate is Na-H-CO3 (molar mass = 84). sodium carbonate is Na-Na-CO3 (molar mass =106) therefore: to get the same amount of sodium you need to 168 grams of baking soda to get the same amount of sodium if you used 106 grams of sodium carbonate. In other words you need 1.58 times of sodium bicarb instead of than the amount of sodium carbonate in your slurry recipe. All of this is based on the assumption that both the sodium carbonate and the sodium bicarbonate are "dry" solids; that is they have no water attached to the molecule. Sodium carbonate is more likely to absorb water than baking soda but both can /and will/ pickup water and still be a "dry" solid. Both are white powders that will absorb water vapor from the air if not stored in a sealed container. I have no useful insight if the reason for using sodium carbonate is adjust the pH of a slurry to control suspension of the solids. I seldom care about suspension as I apply "paste" instead of "slip" on surfaces. I add the sodium to get the effect of the sodium in the fired surface. Regarding @PeterH question: yes. long ago I began using a water spray of sodium carbonate as a means of controlling the fired effect of surfaces. I ran out of sodium carbonate but had baking soda in the cupboard and used it instead; saved a trip to the store and the results were equivalent. I have been using baking soda more often as it is less damaging to my skin and is available at the grocery store near home. A footnote: once the sodium carbonates are dissolved in water they are no longer "sodium carbonates" but are sodium ions and carbonate ions. the pH is determined by the total collections of ions in the liquid phase. Soluble ingredients other than the sodium carbonates also must be considered. LT