Guest JBaymore Posted January 3, 2016 Report Share Posted January 3, 2016 ...The phrase "it depends" tolls forever in my ears Wise in the ways of The Ceramics, you are. best, .............john Link to comment Share on other sites More sharing options...
Guest JBaymore Posted January 3, 2016 Report Share Posted January 3, 2016 When looking at Phase Equilibrium Diagrams relative to developing glazes, be very aware of the steepness of the gradient near/around the eutectic point. The best areas for exploration have shallow curves,.....which makes the formulation and firing less critical. best, .................john Link to comment Share on other sites More sharing options...
glazenerd Posted January 3, 2016 Author Report Share Posted January 3, 2016 Babs: I will go with holy grail, sounds more pleasant and sane than obsession. Hate to admit it, but I think I crossed into the obsession realm about two years ago. In reality, no one has attempted to do macro crystalline wall tile other than a handful of 4 x 4 or 6 x 6 blended into other store bought tiles. All I do right now are called liners: 6 x 18 pieces that are likewise installed with other tiles. I have done a couple of back splashes entirely in crystalline- which is my artistic goal. Daily living art that you look at every day. Have also done a fireplace with plinths: 12" x 24" pieces that wrap the opening before the mantle and legs are attached. The 50% frit and colorants could be easily calculated with eutectics; that is the easy part of the equation. The hard part is the crystals themselves which are comprised of 25% each of zinc and silica. They are indeed an ionic bond floating around in a sea of eutectic soup. Part of me is looking for the holy grail; but what I am really after is an 85% consistency goal in order to have a marketable product. I can grow crystals, piece of cake. Have yet to figure out however how two pieces of tile sitting on the same shelf, glazed with the same batch can come out so completely different. I expect differences, nature of the glaze- but radical differences? So I decided to join the forum in order to drive people crazy along with me so I am not alone in my insanity. Nerd Link to comment Share on other sites More sharing options...
Guest JBaymore Posted January 4, 2016 Report Share Posted January 4, 2016 I have done a couple of back splashes entirely in crystalline- which is my artistic goal. Daily living art that you look at every day. Have also done a fireplace with plinths: 12" x 24" pieces that wrap the opening before the mantle and legs are attached Do you have any images of this stuff? Couldn't find any in the gallery you have up. (but I tend to be blind . ) Since the growth of the crystals in a given formulation of glaze batch (all tiles in the firing are the same batch) the variables there in the differences in the growth on side-by-side tiles have to be a bit limited. And all relate to the firing end of the beast. Thickness of the substrate is one (tile thickness). Thickness of the raw glaze coating is another. Max. heat work applied to that glaze coating at the peak of the firing (quality of original melt). Cooling rate of any given section of the kiln. (also considering differences in thermal mass of shelves, setters, posts, tile itself) Accuracy of the temperature measurement devices relative to "critical" temperatures (and relating to the thought above). Just thinking out loud. best, ..................john Link to comment Share on other sites More sharing options...
Babs Posted January 4, 2016 Report Share Posted January 4, 2016 No insanity here, we are a dispassionate lot, just looking and taking notes! Link to comment Share on other sites More sharing options...
glazenerd Posted January 4, 2016 Author Report Share Posted January 4, 2016 John: Have a few pics upstairs on my other puter; will put them up shortly. Most I never see, they use installers and I do not see it after delivery. ** Thickness: 1/2" slab rolled- 3/8 final product. Have not deviated from that thickness in over 4 years. ** I have tested from a low of .35G per S.I., up to .75G per S.I. .45G per S.I. seems to be the magic bullet on flat work. ** On cone 6, I began at 2220F, increasing 2F up to 2245F- did the same for cone 10. 2228F is the number. ** On the initial firing in new kilns: I use almost a box of cones. Around the perimeter, and in the center. I know exactly where the hot and cold spots are in each of my four kilns. I use my pyrometer from time to time to calibrate TC offsets. Came up with a little trick two years ago to overcome hot and cold spots. I use a PH meter to check my glaze batches: I know the PH of the "perfect" batch. I lower it .25 in the hot spots, and increase it .25 in the cold spots. Cheap way to adjust for temp variations. In addition, I drop 50F below the soak temp to even out the heat, then ramp back up to my soak temp. ** All my kilns have type S thermocouples, and then see above. Beginning to see how obsessed I am.. running out of things to think about. This I do know, there is something about ionization energy that is playing a role. Just as electronegativity plays a role. I know the clay has an electronegativity value- which I have long questioned it role. I ran a test a month ago with six different porcelain clays- can see a difference in every one. Reason I signed up with Ron Roy- however when I ask him to formulate a clay with an electronegativity value, suspect he will throw me out.. LOL Nerd Link to comment Share on other sites More sharing options...
Guest JBaymore Posted January 4, 2016 Report Share Posted January 4, 2016 Good thermocouples and calibration comments...so that is likely not the issue. Slab cross section tile to tile is constant.... so then maybe look at slab surface consistency or density (are the two side-by-side tiles formed the exact same way? By "thickness" above I meant the glaze deposition layer... not the S.G of the glaze slurry. Meaning the thickness of the powdered glaze layer after it has been applied. Are you testing that after it dries with a micrometer of some sort (penetrometer actually)? If your molten "primordial soup" is over a reef sand bar on one tile and over the Marianas Trench on another... that will for sure impact the results. Sounds like you have a lot of the bases covered better than probably 80% of studio artists. Thinking about this. Can you post two side-by-side tiles photos that show the 'total differences' you are talking about? Does it happen with all colorants... or just some? best, .................john Link to comment Share on other sites More sharing options...
curt Posted January 4, 2016 Report Share Posted January 4, 2016 yes some pics would be good. I assume you are firing electric? I know you are using lots of cones but since you are using radiant heat are those cones really reflecting what the tiles are experiencing in terms of heat work? Ie, cones stand tall while tiles lay flat. Is there a difference between the tiles in the centre of the kiln and those on the outsides near the elements? Perhaps this plays a role. Link to comment Share on other sites More sharing options...
Guest JBaymore Posted January 4, 2016 Report Share Posted January 4, 2016 I know you are using lots of cones but since you are using radiant heat are those cones really reflecting what the tiles are experiencing in terms of heat work? Ie, cones stand tall while tiles lay flat. Is there a difference between the tiles in the centre of the kiln and those on the outsides near the elements? Perhaps this plays a role. Good stuff, curt. There will be some thermal lag on the heating cycle between the cones and the shelves......... and hence with the intimate contact that tiles have with shelves they are lying upon....... the tiles also. And this thermal lag will also be a factor in the cool down cycle, with the thermal mass of the shelves retarding to cooling of the tiles compared to the reading on a thermocouple. Unless there is a surface contact thermocouple or an optical one used on the tiles... the exact temperature of the tiles at any point are open to some "interpretation". Part of what is maybe happening here is that we seem to be approaching what might amount to laboratory and industrial standards issues with what amounts to "studio pottery" (read that as sort of like "amateur level" -no disrespect intended to studio potters there-) tools. The reason I tell students that the correct answer to every question in ceramics is always, "It depends", is because there are SO many variables that come into play at so many parts of the process... many of which we are likely totally unaware about.... that results can seem to come out of the blue. best, ...............john Link to comment Share on other sites More sharing options...
glazenerd Posted January 4, 2016 Author Report Share Posted January 4, 2016 Put more examples up in my gallery. Nerd Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted January 9, 2016 Report Share Posted January 9, 2016 Looks like you have lost some small crystals in the glass. I have always found colouring oxides to be good fluxes in small additions. Do you think it is allowing the crystals to stay in the melt or stopping them forming some other way? Link to comment Share on other sites More sharing options...
Guest JBaymore Posted January 10, 2016 Report Share Posted January 10, 2016 In this case, I applied 2 coats of glaze; then added the cadmium and applied the final coat after the initial coats had dried. Cadmium What? CdS? Cerdec stain? In what form? And so on. best, .....................john Link to comment Share on other sites More sharing options...
bciskepottery Posted January 10, 2016 Report Share Posted January 10, 2016 Sounds like some nasty stuff . . . http://www.cdc.gov/niosh/ipcsneng/neng0404.html Link to comment Share on other sites More sharing options...
Guest JBaymore Posted January 10, 2016 Report Share Posted January 10, 2016 Glaze Nerd, I assume that you know this stuff... but there are many folks reading these postings/thread that might not: http://www.sciencelab.com/msds.php?msdsId=9923232 Note that the new CDC TWA for airborne CdS is 0.002 ......the TWA exposure limit for lead oxide is 0.05. CdS is some seriously dangerous stuff. best, .....................john Link to comment Share on other sites More sharing options...
glazenerd Posted January 10, 2016 Author Report Share Posted January 10, 2016 John: Yes, did my research well in advance. Not something I would recommend unless you are educated and equipped for it.With that said; it is insoluble in water, and it was rendered into a paste upon arrival. In addition, it is located separately in a locked-fire proof cabinet. I store left over glazes that contain hazardous materials separately, so they can be thermally decomposed and solidified.Have read the EPA rules, including handling, storage, and disposal. You are correct to bring up the safety issues; been involved with so many lead and asbestos abatements over the years in construction; have gotten use to handling these things. Given the concerns; pulled down the posts. Link to comment Share on other sites More sharing options...
Babs Posted January 10, 2016 Report Share Posted January 10, 2016 Was going to ask if you are still doing these with splashbacks in mind... re. cadmium and the glaze in 1 has crazing.... Can that be "mended" so that it is suitable for a splashback surface in a food prep area and still retain the crystals you are after? Just asking... Hate cleaning grouted tiles if the grout is visible!!! Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted January 10, 2016 Report Share Posted January 10, 2016 I think by the time anybody is getting onto buying Cadmium sources they would have the knowledge at least to learn about its usage/safety even if they don't know it. Here we have the luxury to see into others studios and practices and share in some hyper-web of ceramics information and ideas. You put something out there and people get to add to the soup. There is a saying round here 'what you don't know can kill you' I don't feel the safety concerns were about the cadmium posts being taboo but in the line of sharing information for everybody to make it clear what you are doing is not to be taken lightly. I would hope any crystal glazer would read through the whole thread and not see the one post about cadmium and run out to get some. Do you add this paste to your glaze or is it a paste that you use by itself on top of glaze. Link to comment Share on other sites More sharing options...
Babs Posted January 10, 2016 Report Share Posted January 10, 2016 High Bridge, there is a responsibility here. ie posting without warning of the dangers of materials and practices. Cannot assume knowledge and action of others. Hoping that everyone will act in a certain way isn't enough. Evidence is all around on that line of thinking. Glaze Nerd did the right thing in removing the post. A responsible move on his behalf. I worry being old, that the containers in my shed are not labelled well and whoever cleans up when I fly the coop is therefore in danger. Doing something about this daily. It is a luxury to be part of this incredibly generous, group of people, but along with this goes the responsibility and consequences of what one posts here. Link to comment Share on other sites More sharing options...
glazenerd Posted January 10, 2016 Author Report Share Posted January 10, 2016 Babs: On occasion my patience fails me; and these first test trials were one )more) time- opened the kiln at 300F. Babs: many larger pharmacies usually have "toxic" stickers you can buy to apply to your jars. Mine are stored in a locked cabinet, and plainly marked. Joel: I read extensively about all the materials I use; regardless of their toxicity. Yellow zinc is commonly used in the USA, and has small amounts of CdS, as well as Pb. In fact, CdS is processed from sphalerite; the common zinc ore in the States. The human body needs zinc to break down proteins, plants need it to convert sunlight into chlorophyll. The big problem with zinc is aquatic life: highly toxic to marine life. So when the EPA dumped 5 million gallons of sphalerite into a river in Colorado last year: they lied saying it had no impact on marine life. The same EPA that said- do not breath this- is the same one that dumped 5 million gallons of it into a river. Should not breath any dust- that is the basic rule. Will send you how to make paste from toxic materials; do not think I will post it here. -The moderators are correct in pointing out the toxicity- many just pass through without the knowledge of handling materials safely. Should have pointed it out myself- have just gotten use to being around and handling toxic materials. Nerd Link to comment Share on other sites More sharing options...
Babs Posted January 10, 2016 Report Share Posted January 10, 2016 Ah Glaze Nerd, you cracked the kiln before the hallowed temp...... I was worried for you in that you were being blinkered by crystals I have a new kiln and so am babying it along, trying to leave it alone till it drops, and man it takes a long time to drop! How long this babying lasts....... Thanks for the bit re. stickers. I tend to get a sharpie and draw a quick skull and bones or 3 on the containers. Daughter has a doc. in chem so she should be alright but impatient partner is a "clear the decks quickly" sort of person and so that is my concern. Link to comment Share on other sites More sharing options...
Tim T Posted January 11, 2016 Report Share Posted January 11, 2016 I haven't played with crystal glazes, but a couple of thoughts that may be relevant: - cones only measure firing up, not down - the cone will not return to vertical as the kiln cools, so you cannot see if one part of the kiln is cooling faster than another - tiles nearer the walls of the kiln will ave a different firing cycle than those nearer the centre. On cooling, those at the edge are exposed to a larger thermal mass of the kiln wall plus shelves, so you would expect cooling to be slower. On the way up, things are more complex as it is closer to the heat source, but also the kiln walls are soaking up heat as well as the shelf and tile - could unevenness in the tile and/or glaze act as seed points for crystal growth, and so the number of crystals and their size? Link to comment Share on other sites More sharing options...
Colby Charpentier Posted January 24, 2016 Report Share Posted January 24, 2016 In reality, no one has attempted to do macro crystalline wall tile other than a handful of 4 x 4 or 6 x 6 blended into other store bought tiles. https://cfileonline.org/crystal-tile-london-contemporary-ceramic-art/ Link to comment Share on other sites More sharing options...
glazenerd Posted January 24, 2016 Author Report Share Posted January 24, 2016 That explains a mystery. Link to comment Share on other sites More sharing options...
glazenerd Posted February 3, 2016 Author Report Share Posted February 3, 2016 After doing a series of test, I have concluded that CdS reacts strongly with TiO2 (titanium dioxide). I have tested with standard colorant combinations with little to no effect. However, when mixed with high percentages of TiO2, dramatic changes occur. The two test tiles show have exactly the same colorant combinations of : Rutile 4%, Nickel Ox 0.50%, and 0.25% TiO2. There were fired in the same kiln with the same firing schedule. Tile 1 shows the usual results with this colorant combination, and tile 2 is the same colorant combination with 1% CdS addition. Anyone care to venture a guess as to why the extreme reaction and change? Note: Cadmium is highly toxic and should not be handled unless full safety precautions are observed. Nerd Link to comment Share on other sites More sharing options...
Tyler Miller Posted February 4, 2016 Report Share Posted February 4, 2016 Zinc + cadmium makes green. To elaborate further. Zinc's a difficult flux to get to produce a lot of colours in the usual way. It's one of the reasons why it's not a terribly popular flux outside of its usual applications. Zinc cadmium sulfide is a greenish yellow used in artists pigments on its own as "Yellow 35," and in combinations with various bluish greens to produce a very pure green known as "cadmium green." Zinc cadmium sulfide is variable in coloration depending on how it was produced, varying from a more lemony yellow to a pea green colour. Its most famous use was by the US and UK militaries on their populations to conduct chemical warfare dispersal tests (seriously). Its ability to fluoresce, even in small quanitites, was why it was used as a marker chemical for these tests. In the case of your tiles above. You've got green in the form of nickel oxide, and then the zinc-cadmium combination, and then rutile, the impurities of which are likely also contributing to the green. The TiO2 should be relatively inert as its undissolved particles in the glaze provide the "seeds" for the crystals to form in a macrocrystalline glaze. Cadmium's tricky stuff in that it can, with the right combination, produce every colour in the spectrum, and zinc just happens to help make it green. This property's exploited most commonly in the form of fluorescent quantum dot suspensions. Link to comment Share on other sites More sharing options...
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