Babs Posted March 9, 2019 Report Share Posted March 9, 2019 Ok sucked me in. Explain because ph is not a simple concept. A farmer in high acidic non wetting sand here who at present excavating clay to spread broad acres which inturn gives me a great soil profile pit to gaze upon. Subsoil dry as a limeburner's boots the depth of the pit. So straight Chem doesn't necessarily do the trick Link to comment Share on other sites More sharing options...
glazenerd Posted March 9, 2019 Report Share Posted March 9, 2019 Babs: the secret of maneuvering the rabbit hole is rejecting information that is not clay/ glaze specific. I do not care about the metes and bounds of PH, other than how it effects clay. alkalinity in clay= negative particle charge = plasticity. Alkalinity in slip= suspension, and as PH is spiked by the addition of sodium silicate or synthetic polymers (Darvan) = particle alignment increases because of higher negative charges. The specific gravity changes as the negative particle charge increases, because higher alkalinity creates stronger negative ionic charges. acidity = flocculation! because acidity lowers the negative charge in the clay water film, which in turn creates attraction between clay particles! resulting in flocs forming. I will post the effects of sodium and calcium in my slip chemistry thread. That seemed to be a curve ball. Link to comment Share on other sites More sharing options...
Hulk Posted March 9, 2019 Report Share Posted March 9, 2019 uh-oh Link to comment Share on other sites More sharing options...
njabeid Posted March 9, 2019 Author Report Share Posted March 9, 2019 While we're here, an incidental question about clay: that white clay, when wet, has a strong and pleasant smell; some women in the region eat it (mostly when pregnant I think), and say it's addictive. Commercial kaolin in the UK has a different, fainter smell. The only other mineral smell I remember is one associated with an old childhood memory from Ottawa, and found again in a cave behind Niagara Falls. Both smells are kinda related, but not the same. Any clues? Link to comment Share on other sites More sharing options...
glazenerd Posted March 9, 2019 Report Share Posted March 9, 2019 Calcium in the natural form- calcite, and potassium.. Both found in a cave in So. missourri that I have explored many times: so yes I am familiar with that scent. Actually the lack of a "moldy" smell tells me that clay bed has been around awhile. Link to comment Share on other sites More sharing options...
Babs Posted March 10, 2019 Report Share Posted March 10, 2019 Yeh I get that re ph and the specific gravity when one fiddles to allow more material to be suspended in a given amount of water by using an alkaline material. Then there's viscosity..but down my shed on a given day....I just use observation a lit and the rest on days when. Something other than bats hit the fan:-)) Go Nerd we love it Link to comment Share on other sites More sharing options...
Hulk Posted March 10, 2019 Report Share Posted March 10, 2019 ...me stopped on running fans in the studio... ...mostly on account o' kicks up dust. mostly! Link to comment Share on other sites More sharing options...
Babs Posted March 10, 2019 Report Share Posted March 10, 2019 So there is a way of stopping the s... hiting the fan.. get rid of the fan!!!!!! Bats...fauna type:-))) Link to comment Share on other sites More sharing options...
njabeid Posted March 11, 2019 Author Report Share Posted March 11, 2019 Just found the analysis of the white clay : Link to comment Share on other sites More sharing options...
glazenerd Posted March 11, 2019 Report Share Posted March 11, 2019 Congrats; you have a fine grained alluvial earthenware clay. Tom Link to comment Share on other sites More sharing options...
Benzine Posted March 12, 2019 Report Share Posted March 12, 2019 On 3/8/2019 at 5:30 PM, glazenerd said: Babs: " it depends" is what started my obsession. I fire crystalline glaze; and the same recipe changed every time I fired it on a different porcelain. I came to the conclusion that yes it does depend: depends upon the chemistry of each clay body. I now have access to the Americam Ceramic Society Journals: the rabbit hole has new furniture:) example: did you know when you measure the specific gravity of slip; you are actually measuring the effects of PH? Tom Is this because of how the particles are attracting/ repelling each other, due to charge? Link to comment Share on other sites More sharing options...
glazenerd Posted March 12, 2019 Report Share Posted March 12, 2019 Benz: not sure if you are asking about the chemistry of clay bodies, or the effects of PH in slip? The easiest way to understand either is to look at all those specific terms such as: electron volts, bond energy, cations, anions- as magnets. Every molecule has a positive and negative charge; just as every element ( silica, potassium, sodium, lithium, iron, zinc) has strong to weak magnet pull. In the case of crystalline glaze: zinc has the strongest magnetic field: which attracts the weaker magnet to it which is silica. The reason lithium is used as a flux: it is the weakest, and does not influence the attraction between zinc and silica. Porcelain bodies influence it because of the type and amount of fluxes used in them. Sodium (Nep Sy) in porcelain has a strong magnetic field that disrupts the formation of zinc and silica. Most all glazes are covalent bond or they are chemically bond (eutectic melt). Crystalline glaze is an ionic bond: which means they are formed by the magnetic attraction between elements. Any element with a strong magnetic (atomic) field can disrupt the bond. in slip chemistry; increasing the PH does in fact increase the surface charge ( magnets again) of the particles. I will use grains of rice as an illustration of clay particles. The sides of the grain would be positively charged, and the ends would be negatively charged. If you mixed clay and silica and poured it out: it would be pouring a cup of rice on the counter: no defined arrangement of the particles. If you mixed clay, silica, and flux ( sodium or potassium) and poured it out: some of the grains would be arranged in order, some would not. Once you add a flux, you are increasing the PH: when you increase the PH, you are increasing the magnetic field. Now when you add sodium silicate: the PH spikes, which in turn spikes the negative charge in the water film: and all the rice (clay) aligns as if you took the time to stack them neatly. The term is called particle stacking, the magnetic attraction is called bond energy. Just like any magnet: negative attracts positive. The water film is negative: so the positive edges of the clay ( rice) stacks in perfect positive order. For the same reason above: porcelain has memory. The sodium flux in this clay body creates a strong negative charge in the water film. When you throw, or slab roll porcelain: you distort that magnetic particle arrangement. So after you finish forming and it dries: the magnetic stacking tries to reform: which results in warping. for the record: most porcelain bodies are 8.25 up to 8.40PH. When you use them as slip and add sodium silicate: it spikes to just under 10 PH. So what is perceived and measured as thinning: is actually particles stacking in perfect ionic order. When particles are disordered, it measures thicker. So in reality: viscosity is measuring particle alignment caused by PH increasing the negative charge. Tom Link to comment Share on other sites More sharing options...
njabeid Posted March 12, 2019 Author Report Share Posted March 12, 2019 19 hours ago, glazenerd said: Congrats; you have a fine grained alluvial earthenware clay. Tom But it vitrifies at 1150°C. Does that make any sense? Link to comment Share on other sites More sharing options...
njabeid Posted March 12, 2019 Author Report Share Posted March 12, 2019 On 3/6/2019 at 7:50 PM, glazenerd said: So I would look at a native clay mix of 60% sandy clay, 25% whitish clay and 15% river clay to start. I'm making a batch of this - hard work slaking, screening (stones!), drying before weighing, mixing. Here are the test tiles : I'll make one of the blend once it's complete. The river clay has already cracked while drying! You mentioned bentonite - I have some. Would that help? Link to comment Share on other sites More sharing options...
glazenerd Posted March 12, 2019 Report Share Posted March 12, 2019 Yes it does. Flux levels play a big role in vitrification, but so does particle size. Potters are use to dealing with 200-325 mesh, etc. the general theory being 325 melts faster than 200 mesh, etc. when you deal with clay; you are dealing with microns. If you converted the microns found in clay to mesh: 20,000 to 30,000 mesh. Link to comment Share on other sites More sharing options...
glazenerd Posted March 12, 2019 Report Share Posted March 12, 2019 Yes bentonite would help: maximum of 3% or recipe. Disperse dry and blend before adding water. by the way: looking at your river clay ( brownish) very possible you have magnetite .(iron) in it. Magnetite has a brown/ gray cast. Link to comment Share on other sites More sharing options...
njabeid Posted March 12, 2019 Author Report Share Posted March 12, 2019 How much as a percentage of dry ingredients? Link to comment Share on other sites More sharing options...
njabeid Posted March 12, 2019 Author Report Share Posted March 12, 2019 Sorry, you answered already. Thanks Link to comment Share on other sites More sharing options...
Babs Posted March 12, 2019 Report Share Posted March 12, 2019 8 hours ago, Benzine said: Is this because of how the particles are attracting/ repelling each other, due to charge? Nerd explained it. Re altering charge of ions Particle alignment occurs by compression.aka stopping s cracks in base of pots. Wedging. Aligns particles great for throwing pots as does coning. Prevents warping I guess. Compressing occurring there too..particles stacked not randomly placed Then the chemical stuff above. What I havent thought about is why a lid thrown upside down shrinks more than the pot...... Link to comment Share on other sites More sharing options...
Benzine Posted March 13, 2019 Report Share Posted March 13, 2019 14 hours ago, Babs said: Nerd explained it. Re altering charge of ions Particle alignment occurs by compression.aka stopping s cracks in base of pots. Wedging. Aligns particles great for throwing pots as does coning. Prevents warping I guess. Compressing occurring there too..particles stacked not randomly placed Then the chemical stuff above. What I havent thought about is why a lid thrown upside down shrinks more than the pot...... Yeah, I asked the question, thinking that it was his last post, not seeing there were more replies... The internet has only been around for 30 years, eventually I'll get the hang of it... Link to comment Share on other sites More sharing options...
Babs Posted March 13, 2019 Report Share Posted March 13, 2019 Well my question is.unless diving down rabbit holes some of the stuff needs thinking about but not a great depth unless that's your baby. Like compress bade no base cracking.. We drive cars efficiently but dont at least I dont know all the knwlwdge that goes into the making of that car. Can change wheels ,jump start , chane oil etc but stops there Link to comment Share on other sites More sharing options...
glazenerd Posted March 13, 2019 Report Share Posted March 13, 2019 BUT, unlike cars; when your clay breaks down there is no shop to take it to. Link to comment Share on other sites More sharing options...
njabeid Posted March 16, 2019 Author Report Share Posted March 16, 2019 I've got the clay blend, with 58% sandy clay instead of 60. I have started throwing with it, and it holds up really nicely but I find it a bit too sandy and definitely short, kind of woolly or fuzzy when trimming. I had previously tried a blend of 50% river clay, 40 % white and only 10% sandy, and it is much smoother. More work ahead, firing them and trying them with the suggested engobe. This is Tom's blend, smoothed with a flat metal rib and an agate : and this is my blend, just as green but a bit drier ; I'll get back with more info after more tries. Is the shrinkage of the test tiles in percentage (see earlier post) the COE ? Sorry, silly question, but sometimes simple things are made to sound nerdy. This is all very interesting and useful for me, thanks! Link to comment Share on other sites More sharing options...
liambesaw Posted March 16, 2019 Report Share Posted March 16, 2019 The shrinkage is just the shrinkage, which is good to know Link to comment Share on other sites More sharing options...
glazenerd Posted March 16, 2019 Report Share Posted March 16, 2019 Link to comment Share on other sites More sharing options...
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