Crooked Lawyer Potter Posted October 12, 2022 Report Share Posted October 12, 2022 Never thought too much about it, but I I always assumed that one would never get a specific gravity reading that was less than 1.0 since the water was "the base" and any particulates would be added to its weight. But my recent ball clay terra sig is showing me a SG of 0.87 Is that possible? Or have I mis-read my results? If correct, is this because the very small clay particles (1) displace water and (2) weigh less than H2O? Quote Link to comment Share on other sites More sharing options...
Magnolia Mud Research Posted October 12, 2022 Report Share Posted October 12, 2022 my guess is that the mixture has expanded, which some clays will do when wetted; have seen some clay that expanded double in size when wet. LT Quote Link to comment Share on other sites More sharing options...
Min Posted October 12, 2022 Report Share Posted October 12, 2022 Vince Pitelka super refined Terra Sig specific gravity of 1 - 1.2 using a specialized lab hydrometer. Link here to his article with all the details. Magnolia Mud Research 1 Quote Link to comment Share on other sites More sharing options...
Crooked Lawyer Potter Posted October 12, 2022 Author Report Share Posted October 12, 2022 Reading Vince's article suggests to me that SG less than 1.0 is NOT possible since the hydrometers he mentions all have scales that start at 1.0. Still hoping someone can answer this question authoritatively -- is it possible to get SG less than 1.0? Quote Link to comment Share on other sites More sharing options...
PeterH Posted October 12, 2022 Report Share Posted October 12, 2022 How are you measuring the SG? I've read several times that you cannot/shouldn't rely on hydrometers when measuring slips (i.e liquids with complex rheology). If you did use a hydrometer can you recheck using a syringe and scale? Quote Link to comment Share on other sites More sharing options...
Crooked Lawyer Potter Posted October 12, 2022 Author Report Share Posted October 12, 2022 I used a syringe and scale. I'm getting used to the idea that it CAN be less than 1.0 since as I just read SGis a measure of "relative density" and if the "solute" i.e the material floats in the solution it means it is less than 1.0 and if it sinks in the solution it is greater than 1.0 I guess the tiny platelets of clay are less dense than water and thats why they stay suspended (i.e. float) in the liquid. But I will wait to hear from someone who actually knows what they are talking about. Quote Link to comment Share on other sites More sharing options...
Min Posted October 12, 2022 Report Share Posted October 12, 2022 1 hour ago, Crooked Lawyer Potter said: But I will wait to hear from someone who actually knows what they are talking about. Take it for what's it worth and do the math. Figure out by percentages what the specific gravity of you terra sig materials are. Sounds like user error to me, doesn't make sense your sg is below one given ball clay has a sg of 2.5 - 2.6 BTW people are just trying to help here. List of common ceramic materials below to work your equation from. List of specific gravities Silica 2.6 - 2.65 Kaolin 2.6 - 2.65 EPK 2.65 Grolleg 2.6 Ball Clay 2.5 - 2.6 Bentonite 2.2 - 2.8 Calcined Alumina 3.7 - 3.9 Alumina Hydrate 2.42 Whiting 2.8 Feldspar 2.55 - 2.75 Granite 2.66 Wollastonite 2.8 – 3.09 Talc 2.58 - 2.83 Magnesium Carbonate 3 - 3.1 Light Magnesium Carbonate 2.24 Dolomite 2.9 Zinc Oxide 4.4 - 5.6 Barium Carbonate 4.27 - 4.43 Strontium Carbonate 3.5 - 3.7 Titanium Dioxide 4.2 Tin 6.85 - 6.95 Red Iron Oxide 4.9 - 5.3 Cobalt Carbonate 4.13 Cobalt Oxide 6.07 - 6.66 Copper Carbonate 3.9 - 4 Black Copper Oxide (CuO) 6.4 Red Copper Oxide (Cu2O) 6 Hulk 1 Quote Link to comment Share on other sites More sharing options...
Crooked Lawyer Potter Posted October 12, 2022 Author Report Share Posted October 12, 2022 1 hour ago, Crooked Lawyer Potter said: I used a syringe and scale. I'm getting used to the idea that it CAN be less than 1.0 since as I just read SGis a measure of "relative density" and if the "solute" i.e the material floats in the solution it means it is less than 1.0 and if it sinks in the solution it is greater than 1.0 I guess the tiny platelets of clay are less dense than water and thats why they stay suspended (i.e. float) in the liquid. But I will wait to hear from someone who actually knows what they are talking about. 2 minutes ago, Min said: BTW people are just trying to help here. You would think that a lawyer could communicate better than i have here. I meant to express that my musings about “tiny platelets” was just the uninformed ramblings of a non expert and should not be taken as authoritative. Instead, i just came off sounding like an ungrateful ########. My apologies to those who were offended by my careless language. Quote Link to comment Share on other sites More sharing options...
Crooked Lawyer Potter Posted October 12, 2022 Author Report Share Posted October 12, 2022 36 minutes ago, Min said: doesn't make sense your sg is below one given ball clay has a sg of 2.5 - 2.6 Min Good point. But consider -- this is just the smallest (and presumably lightest) elements of the ball clay. Quote Link to comment Share on other sites More sharing options...
PeterH Posted October 12, 2022 Report Share Posted October 12, 2022 Can we check your figures, as SG<1 seems rather unlikely. What are you measuring, and what where the values? Quote Link to comment Share on other sites More sharing options...
Crooked Lawyer Potter Posted October 12, 2022 Author Report Share Posted October 12, 2022 I draw 50 ml of the terra sig into my syringe and weigh it. It weighs 70 mg. I subtract the weight of the syringe (28mg) and then double the number, as in: (70 - 28 = 42) x 2 = 84 Quote Link to comment Share on other sites More sharing options...
Dick White Posted October 12, 2022 Report Share Posted October 12, 2022 Have you tared the scale to zero with the empty syringe on it? If so, then subtracting the 28g for the weight of the syringe has already been done by the scale. Even then, it isn't making sense. 2 X 70g would give a S.G. 1.4, which is almost glaze slurry consistency, or waaay too thick for terra sig. And just for theory, the specific gravity of water plus a solid in suspension cannot be less than 1.0 unless the solid is actually floating on top and thus displacing more water in the syringe than it weighs. As noted above by Min, clay (regardless of the particle size) has a density/specific gravity in the 2.6 range. Babs 1 Quote Link to comment Share on other sites More sharing options...
PeterH Posted October 12, 2022 Report Share Posted October 12, 2022 1 hour ago, Crooked Lawyer Potter said: I draw 50 ml of the terra sig into my syringe and weigh it. It weighs 70 mg. I subtract the weight of the syringe (28mg) and then double the number, as in: (70 - 28 = 42) x 2 = 84 Can you repeat the measurement process again? Once with t-sig and once with water? Quote Link to comment Share on other sites More sharing options...
Min Posted October 12, 2022 Report Share Posted October 12, 2022 (edited) 2 hours ago, Crooked Lawyer Potter said: It weighs 70 mg. I subtract the weight of the syringe (28mg) and then double the number 70 mg (micrograms) would be 0.07 g (grams) or sometimes abbreviated to gm, I believe you meant 70g for the terra sig and 28g for the syringe? Edited October 12, 2022 by Min Quote Link to comment Share on other sites More sharing options...
Crooked Lawyer Potter Posted October 12, 2022 Author Report Share Posted October 12, 2022 1 minute ago, Min said: 70 mg (micrograms) would be 0.07 g (grams), I believe you meant 70g for the terra sig and 28g for the syringe? Correct. My error. Quote Link to comment Share on other sites More sharing options...
Kelly in AK Posted October 13, 2022 Report Share Posted October 13, 2022 As I understand it, clay particles, no matter how tiny, don’t become less dense than water. The smallest ones are colloidal and stay in suspension by Brownian motion. A well sealed jar of terra sig after many months will either still be in suspension or have settled a bit. I’ve never seen a part “rise to the top” like cream. Quote Link to comment Share on other sites More sharing options...
Crooked Lawyer Potter Posted October 13, 2022 Author Report Share Posted October 13, 2022 2 hours ago, PeterH said: Can you repeat the measurement process again? Once with t-sig and once with water? Will do. Quote Link to comment Share on other sites More sharing options...
Crooked Lawyer Potter Posted October 13, 2022 Author Report Share Posted October 13, 2022 3 hours ago, Dick White said: Have you tared the scale to zero with the empty syringe on it? Yes. 3 hours ago, Dick White said: Even then, it isn't making sense. 2 X 70g would give a S.G. 1.4, which is almost glaze slurry consistency, or waaay too thick for terra sig. I'm not doubling 70. I take the reading of 70 and subtract the weight of the syringe. I then double that number. (42x2=84) Quote Link to comment Share on other sites More sharing options...
Crooked Lawyer Potter Posted October 13, 2022 Author Report Share Posted October 13, 2022 Mystery solved! I weighed the syringe again and found the error. I had recorded its weight as 28g but its actually 23g and a re-weigh of the full syringe was 75g this time not 70 as before. So, 75 less 23 is 52 x 2 is 104. Thanks to you all for your input. I'm going to assume that SG cant be less than 1 after all. Hulk 1 Quote Link to comment Share on other sites More sharing options...
Babs Posted October 13, 2022 Report Share Posted October 13, 2022 36 minutes ago, Crooked Lawyer Potter said: CROOKED Lawyer To his question Did you tare the scales, you answered Dick Yes. I'm not doubling 70. I take the reading of 70 and subtract the weight of the syringe. I then double that number. (42x2=84) @Crooked Lawyer Potter You state you have tared the scale ,Dick's 1st question and then go on to take the weight of syringe off again in second part of your reply. If tare scale , don't then take weight of syringe off before x 2.. Or is this my misinterpretation? Quote Link to comment Share on other sites More sharing options...
Crooked Lawyer Potter Posted October 13, 2022 Author Report Share Posted October 13, 2022 4 hours ago, Dick White said: Have you tared the scale to zero with the empty syringe on it? If so, then subtracting the 28g for the weight of the syringe has already been done by the scale. Even then, it isn't making sense. 2 X 70g would give a S.G. 1.4, which is almost glaze slurry consistency, or waaay too thick for terra sig. And just for theory, the specific gravity of water plus a solid in suspension cannot be less than 1.0 unless the solid is actually floating on top and thus displacing more water in the syringe than it weighs. As noted above by Min, clay (regardless of the particle size) has a density/specific gravity in the 2.6 range. Yes i tared the scale. Quote Link to comment Share on other sites More sharing options...
Crooked Lawyer Potter Posted October 13, 2022 Author Report Share Posted October 13, 2022 32 minutes ago, Babs said: You state you have tared the scale ,Dick's 1st question and then go on to take the weight of syringe off again in second part of your reply. If tare scale , don't then take weight of syringe off before x 2.. Again, my bad. Careless response. I just meant that when i weigh the syringe, the scale is tared to zero. In other words, the reading i get is the weight of the syringe and its contents. And since i know (or thought i knew) the weight of the syringe, i subtract the syringe weight to determine the weight of the 50g of terra sig in the syringe. Quote Link to comment Share on other sites More sharing options...
Babs Posted October 13, 2022 Report Share Posted October 13, 2022 28 minutes ago, Crooked Lawyer Potter said: Again, my bad. Careless response. I just meant that when i weigh the syringe, the scale is tared to zero. In other words, the reading i get is the weight of the syringe and its contents. And since i know (or thought i knew) the weight of the syringe, i subtract the syringe weight to determine the weight of the 50g of terra sig in the syringe. Ok. Why not get any container, tare to zero with container on board. Add 100ml of whatever then move decimal point accordingly to get the SG...just saying Quote Link to comment Share on other sites More sharing options...
Babs Posted October 13, 2022 Report Share Posted October 13, 2022 Anoyher thing is if terra sig is pure then a bit of a stir , fine. If colourant added, need a big stir as syringe may be sucking more dense stuff from bottom. Quote Link to comment Share on other sites More sharing options...
Crooked Lawyer Potter Posted October 13, 2022 Author Report Share Posted October 13, 2022 Got ya Quote Link to comment Share on other sites More sharing options...
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