Min Posted July 25 Report Share Posted July 25 23 hours ago, davidh4976 said: The quest continues... Could try contacting ASTM and asking them which test standard is used for water absorption of ceramics other than tile and whiteware/sanitaryware. Email and phone numbers in the link below, might be worth a shot. I realize they might well refer you to the same C373 but might be insightful. https://www.astm.org/contact/ Quote Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted July 26 Report Share Posted July 26 ASTM C373 is the standard for testing ceramics. It doesn't tell you if it's functional, only what you can call it. Kelly in AK, Hulk, Bill Kielb and 1 other 4 Quote Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted July 31 Report Share Posted July 31 I managed to find a bit of research comparing 7 different standards for testing water absorption. It brought up a few questions about not glazing, grinding off the fired surface and freshly breaking the ware before testing. It got me thinking, as potters are we interested in the absolute absorption value of the body or the functional absorption value of the surface with glaze on it? They did a comparison of Unglazed. Original body surface removed - 2.2% Unglaze. Original body surfaces retained 1.5% Glazed on both sides. Edges ground - 0.5% Quote Link to comment Share on other sites More sharing options...
neilestrick Posted July 31 Report Share Posted July 31 2 hours ago, High Bridge Pottery said: I managed to find a bit of research comparing 7 different standards for testing water absorption. It brought up a few questions about not glazing, grinding off the fired surface and freshly breaking the ware before testing. It got me thinking, as potters are we interested in the absolute absorption value of the body or the functional absorption value of the surface with glaze on it? They did a comparison of Unglazed. Original body surface removed - 2.2% Unglaze. Original body surfaces retained 1.5% Glazed on both sides. Edges ground - 0.5% So if I'm reading this correctly, the surface of the unglazed wall is better vitrified than the middle of the wall, which means the heat isn't penetrating fully through the piece. Makes sense to me. What do you mean by edges ground? Did they grind the glaze completely down to the clay? Quote Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted August 1 Report Share Posted August 1 They made disks 75mm diameter and 4mm or 8mm thick fired at 100c/h and then held at 1160 for 8 hours. They found no difference in absorption values between the 4 and 8mm thick samples. They don't specify how much to grind off when removing the surface clay but they do say to remove all glaze on the corners. I am not sure with an 8 hour hold it's so much about heat penetrating fully but they don't really give an explanation for why the surface is less porous only that it is. Quote Link to comment Share on other sites More sharing options...
Bill Kielb Posted August 1 Report Share Posted August 1 50 minutes ago, High Bridge Pottery said: They made disks 75mm diameter and 4mm or 8mm thick fired at 100c/h and then held at 1160 for 8 hours. This is bewildering? Any mention what this body was designed to fire at? Looks like they held cone 4 for eight hours. If this is a cone 10 body then not sure what was being tested. Interesting! Quote Link to comment Share on other sites More sharing options...
Hulk Posted August 1 Report Share Posted August 1 High Bridge Pottery, is the study available on the web? Quote Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted August 1 Report Share Posted August 1 No mention of the clay recipe but they state Quote Two sets of 75mm-dia discs were prepared from the same batch of de-aired plastic body, one of 4mm unfired thickness to represent domestic table-ware, the other of 8mm thickness to represent hotel-ware products. These specimens were divided into four groups for biscuit firing, the aim being to produce groups of identical specimens with water absorption values ranging from about 0.5% to 10%, ie covering the range for most types of ceramics. The specimens were fired to 1100, 1120, 1140 or 1160°c, heating rate 100°c/h, and the peak temperature was held for 8h to minimize variations within the kiln. @Hulk Not sure if it is online anywhere, it's called "A Comparison of Water Absorption Test Procedures - T. Smith and N Leak. 1985" Hulk 1 Quote Link to comment Share on other sites More sharing options...
Bill Kielb Posted August 1 Report Share Posted August 1 (edited) @Hulk Here is some interesting reading on a study by multiple authors - (Brazil) on water absorption research for wall and floor tile and the comparison of testing methods. What was interesting to me is the residence time in general had greater effect than boiling time …….. and full saturation is very difficult to get under present testing methods. An interesting read https://www.scielo.br/j/mr/a/8PWbbHrVk3jqM7CYm3sjDnk/?lang=en# Edited August 1 by Bill Kielb Hulk, High Bridge Pottery and HenryBurlingame 3 Quote Link to comment Share on other sites More sharing options...
HenryBurlingame Posted August 20 Author Report Share Posted August 20 (edited) I’m still having a hard time finding good cone 6 clay bodies. Does anyone know of a company that uses frit in their clay bodies to get full vitrification at cone 6? The clays I have tried have so far had high or uneven absorption, and if they do have good vitrification they reclaim weird (like they are getting short for some reason or something). I don’t want to HAVE to make my own clay bodies but I am starting to think about it lol. Edited August 20 by HenryBurlingame Quote Link to comment Share on other sites More sharing options...
Hulk Posted August 20 Report Share Posted August 20 I'm liking several clays that have low absorption numbers*, particularly IMCO DC 3-5 (1%), Red Velvet Classic (1.7%), and also Terry Clay (<.2%), having tried just one bag, planning to get more next trip! I've reclaimed quite a lot of the DC 3-5 and Red Velvet Classic without issue. I do retain all the slop and such, and have used "reclaim mix" additive, but found restorative additive isn't really necessary for these three clays... *I haven't done absorption tests on these three clays, not since well before the talc reformulations. The numbers are from IMCO, at cone 6, except the Terry Clay, cone 5. Quote Link to comment Share on other sites More sharing options...
PeterH Posted August 20 Report Share Posted August 20 3 hours ago, HenryBurlingame said: I’m still having a hard time finding good cone 6 clay bodies. Does anyone know of a company that uses frit in their clay bodies to get full vitrification at cone 6? The clays I have tried have so far had high or uneven absorption, and if they do have good vitrification they reclaim weird (like they are getting short for some reason or something). I don’t want to HAVE to make my own clay bodies but I am starting to think about it lol. Would tweaking the reclaim be easier than making your own body (which might also have reclaim issues)? Quote Link to comment Share on other sites More sharing options...
HenryBurlingame Posted August 21 Author Report Share Posted August 21 9 hours ago, PeterH said: Would tweaking the reclaim be easier than making your own body (which might also have reclaim issues)? Thanks for the link! Regarding neph sy in the body, someone told me that a lot of midfire clays use a lot of it to get vitrification at cone 6 and all the sodium can cause the trouble with reclaiming. I am wondering if that is the issue I am having... Quote Link to comment Share on other sites More sharing options...
PeterH Posted August 21 Report Share Posted August 21 2 hours ago, HenryBurlingame said: Thanks for the link! Regarding neph sy in the body, someone told me that a lot of midfire clays use a lot of it to get vitrification at cone 6 and all the sodium can cause the trouble with reclaiming. I am wondering if that is the issue I am having... I'll definitely leave that to @Min. However in the posting I referenced she does say: ... but I would test the reclaimed batch for absorption in case it also needs a top up of flux. . BTW it is common to use nepheline syenite as a body flux. So maybe your problem is partly loss of neph sy in the reclaim cycle. Quote Link to comment Share on other sites More sharing options...
Min Posted August 21 Report Share Posted August 21 How are you recycling your reclaim? I'd hazard a guess the majority of using cone 6 bodies have nepheline syenite as the primary flux. PeterH 1 Quote Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted August 21 Report Share Posted August 21 I would guess along with everybody else that you are losing a lot of the finer particles before you are reclaiming. The clays that vitrify better may just have an overall smalller particle size that helps it get to under 1% instead of using more flux. If you did want to experiment with clays I think swapping out 3-5% neph for 3-5% petalite would probably do the trick and possibly cheaper than frit. Quote Link to comment Share on other sites More sharing options...
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