Alyosha Posted January 16, 2022 Report Share Posted January 16, 2022 I've been making a batch of terra sig for the second time from raw clay. I believe the density after mixing the clay and water was about 1.18. After twenty hours sitting however there is no difference in layers in the preparation. I have used for the most part water afloat from my recycling clay buckets already thicker than water. Would it be the reason the deflocculation is taking more time ? Link to comment Share on other sites More sharing options...
Callie Beller Diesel Posted January 16, 2022 Report Share Posted January 16, 2022 What did you use for deflocculation, and how old is it? Link to comment Share on other sites More sharing options...
Alyosha Posted January 16, 2022 Author Report Share Posted January 16, 2022 Hi Callie, i use 0.25 per cent of silicate sodium and 0.25 per cent of sodium carbonate . Both per cent of dry clay weight. About 11 grammes of each . Because the bucket wasn't big enough to put all the dry clay if I remember correctly there's a chance there is more than 0,25 percent of each in the mixture. Would too much deflocculant be the cause ? Link to comment Share on other sites More sharing options...
Alyosha Posted January 16, 2022 Author Report Share Posted January 16, 2022 There was also probably some chlore in the water of the recycled buckets Link to comment Share on other sites More sharing options...
Callie Beller Diesel Posted January 16, 2022 Report Share Posted January 16, 2022 Making sig depends on a few things, mostly particle size distribution of your clay, ph, and temperature. This article describes what happens it in more detail, but the short answer is to try putting it in the freezer for a few minutes, and see if that settles it out a bit better. Without knowing exactly what clay you’re using it’s a little harder to trouble shoot. If you’re using reclaim that has kaolin and/or bentonite in it, that will interfere with your yield. The article talks about using Darvan, which is a dispersant used in North America, but I believe the commercial name for a similar product in the UK is Dispex. From what I could tell, your weights for sodium silicate and soda ash are equivalent. Link to comment Share on other sites More sharing options...
Babs Posted January 16, 2022 Report Share Posted January 16, 2022 Check out quick sigelatta posted by Marcia Selsor on these forums. @ Link to comment Share on other sites More sharing options...
Alyosha Posted January 17, 2022 Author Report Share Posted January 17, 2022 Thank you thank you. I might give it a twirl, check the specific gravity again and put it outside. It is difficult to move without mixing the preparation. Link to comment Share on other sites More sharing options...
Alyosha Posted January 17, 2022 Author Report Share Posted January 17, 2022 I'm thinking I might of made a mistake when preparing the mixture I aimed for a density of 1'18. Maybe it's is too dense for the deflocculation and the batch should be prepared with lower density and only after by evaporation can it get a specific gravity of around 0.18 Link to comment Share on other sites More sharing options...
Alyosha Posted January 18, 2022 Author Report Share Posted January 18, 2022 What are your thoughts please? Link to comment Share on other sites More sharing options...
Babs Posted January 18, 2022 Report Share Posted January 18, 2022 42 minutes ago, Alyosha said: What are your thoughts please? Your mixture looks pretty thick indeed. Like way too thick. Link to comment Share on other sites More sharing options...
Babs Posted January 18, 2022 Report Share Posted January 18, 2022 6 minutes ago, Babs said: Your mixture looks pretty thick indeed. Like way too thick. How long has it been settling? Link to comment Share on other sites More sharing options...
Alyosha Posted January 18, 2022 Author Report Share Posted January 18, 2022 40 hours. Yes it looks too thick however I have measured with a cup of water. It is 118 grams in comparison. So it seems it’s at the good density. Link to comment Share on other sites More sharing options...
Callie Beller Diesel Posted January 18, 2022 Report Share Posted January 18, 2022 @Alyosha If you’re using reclaim scraps, can you check with your supplier to see if there’s any bentonite in their recipe? That will interfere with deflocculating clay. Link to comment Share on other sites More sharing options...
Min Posted January 18, 2022 Report Share Posted January 18, 2022 How was your soda ash stored? If not kept sealed up in an air tight container it will change from sodium carbonate into sodium bicarbonate, which is a flocculant. Link to comment Share on other sites More sharing options...
Alyosha Posted January 18, 2022 Author Report Share Posted January 18, 2022 It's kept in a small plastic jar, a quarter of it is empty though so there's is air inside. For a moment a thought it might of been bicarbonate but it is labelled carbonate Link to comment Share on other sites More sharing options...
Alyosha Posted January 18, 2022 Author Report Share Posted January 18, 2022 @Callie Beller Diesel the green clay was directly took from the ground, it's a low temperature firing clay, I throw it on the wheel and it fires a shade of light brown. I've used inly once a very small amount of bentonite for glazing in the same studio. The problem might come from the waters I used from different reclaim buckets, some had been lightly sprayed with a detergent against the odours a month ago. Link to comment Share on other sites More sharing options...
Min Posted January 18, 2022 Report Share Posted January 18, 2022 Measurements need to be precise with terra sig. Sounds like you have a few variables that could be throwing things off. On 1/16/2022 at 11:20 AM, Alyosha said: Because the bucket wasn't big enough to put all the dry clay if I remember correctly there's a chance there is more than 0,25 percent of each in the mixture. Would too much deflocculant be the cause ? On 1/16/2022 at 11:22 AM, Alyosha said: There was also probably some chlore in the water of the recycled buckets Chlorine? 2 hours ago, Alyosha said: I have measured with a cup of water. It is 118 grams in comparison. For practical purposes 100 ml of water will weigh 100 grams. If you are literally measuring 1 cup (Imperial) of water it would weigh 284 grams. How are you measuring specific gravity. 59 minutes ago, Alyosha said: 59 minutes ago, Alyosha said: The problem might come from the waters I used from different reclaim buckets, some had been lightly sprayed with a detergent against the odours a month ago. This would be another unknown. I'ld suggest putting this batch aside and start a small test batch. Use clean drinking quality water, distilled if possible. Weigh your powdered dry clay and deflocculants really accurately and once mixed leave it for 20 hours then check for separation. Link to comment Share on other sites More sharing options...
PeterH Posted January 18, 2022 Report Share Posted January 18, 2022 Maybe this?Chlor Tabs Effervescent chlorine tabletshttps://www.evansvanodine.co.uk/assets/Chlor-Tabs-is.pdf Contains a blend of troclosene sodium (sodium dichloroisocyanurate) and inert ingredient Link to comment Share on other sites More sharing options...
Magnolia Mud Research Posted January 18, 2022 Report Share Posted January 18, 2022 A very good explanation for the details for making terra-sig is this paper by Vince Pitelka https://vincepitelka.com/wp-content/uploads/2019/05/Super-Fine-Terra-Sigillata-Edited-2019.pdf He explains the basis for 20 hours, and what you are trying to accomplish among the various particles in the slurry. LT Link to comment Share on other sites More sharing options...
glazenerd Posted January 19, 2022 Report Share Posted January 19, 2022 7 hours ago, Alyosha said: @Callie Beller Diesel the green clay was directly took from the ground, it's a low temperature firing clay, I throw it on the wheel and it fires a shade of light brown. I've used inly once a very small amount of bentonite for glazing in the same studio. The problem might come from the waters I used from different reclaim buckets, some had been lightly sprayed with a detergent against the odours a month ago. Alyosha: I work with several groups who harvest locally sourced clay(s). In nature: a greenish color is often associated with calcium bentonite. (Fullers Earth) If it is in fact calcium bentonite: it will stay suspended. Calcium bentonite has much smaller particle size than ball clay(s) normally used in Terra Sig. Sodium silicate and sodium carbonate additions are within tolerance: just as a SG of 1:18 is. Due to the uniformity of particle dispersion over an extended period: high probability you have dug up calcium bentonite/ or calcium hectorite. Calcium alone creates suspension naturally. Tom Link to comment Share on other sites More sharing options...
Alyosha Posted January 19, 2022 Author Report Share Posted January 19, 2022 Thanks all for the help. @Magnolia Mud Research It is the text I followed. A clue about what might be happening is on the surface, the clay seems to have splits , here's a photo. ( Sorry Tom for a false call, I don't know how to take the @ off )@Tom@glazenerd Here is a sheet about the earth, it's from Romainville. I have managed to make it deflocculate by the past in a small jar. Of course it wasn't the same piece of clay though. What would happen if there's is too much deflocculante agents? I error could be that I took the suspended water from a bucket of beige earth, maybe travertin, that was a layer on top of the clay, there it might happen that there is bentonite then. @Min Yes I might of made a mistake during preparation. There was a fair amount of work in order to 80 mesh such quantity of raw clay but it seems indeed that I have to start again, in smaller quantity. With this batch I could perhaps try taking half of the bucket and adding water mixing it a tad more deflocculante and leave it outside. @PeterH The detergent used a few sprays of q month ago is composed of 0,99% Chlorure didectldimethylammonium and les than 5% non ionic surface agent and phosphonates and limonele, linalool. Link to comment Share on other sites More sharing options...
glazenerd Posted January 20, 2022 Report Share Posted January 20, 2022 Alyosha: The analysis you posted falls close to a hectorite. 18% dolomite: which supplies calcium and magnesium- both natural deflocculants. Glauconite is iron rich mica: also high in potassium- which aids in suspension. 17% bentonite (last line in spec sheet) which is a suspension agent. I would expect this clay to stay suspended without adding any additional deflocculants. Careful firing over cone 04: this clay has very low alumina levels- which would turn to a molten blob quickly. Tom Link to comment Share on other sites More sharing options...
oldlady Posted January 20, 2022 Report Share Posted January 20, 2022 alyosha, would you mind saying where you are in the world? we won't come knocking at your door or send trouble your way. i like to think of members of this community in their places in the world, i bet others like that, too. the language on your chart looks like French but i am the worst at languages. could you be in canada? Link to comment Share on other sites More sharing options...
Alyosha Posted January 20, 2022 Author Report Share Posted January 20, 2022 Hello @oldlady, yes I live in France, Romainville is small town sharing borders with Montreuil and Paris. Link to comment Share on other sites More sharing options...
Alyosha Posted January 20, 2022 Author Report Share Posted January 20, 2022 Hi @glazenerd, Indeed I’ve fired the clay by guess to around 800 Cº , it came out good although feels slightly underfired compared to high temp grès. I was told it could be fired to 900Cº. I wonder now if it could stand a proper cone 04. Can I add alumina to it as I did with sand ? When you mean the clay could stay suspended, could I then make Terra Sig from without any deflocculante, with a suffisant amount of water at the right ph ? Link to comment Share on other sites More sharing options...
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