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Everything posted by AmeriSwede

  1. First my disclaimer, tluvs. Though I don't profess to be a professional with or know all about slip casting, I do have a few years of experience under my belt, all with commercial molds though. Additionally, I've many many years experience with casting wax, metals and glass, and some problems seem inherent in some of these materials as well. One thing that I've learned through the years is that when one has interior planes intersecting at sharp interior angles, because of shrinkage of the cast materials, this can often place additional stress on the material, resulting in cracks. The cracks normally show as an extension of the planes themselves... pretty much as the cracks in your cross tiles. In this illustration the forces of shrinkage (magenta arrows) show how the clay cross is drying and pulling away from the sides of your mold. Notice that this force can continue at the acute interior angle as the forces of one arm of the cross pull away from the forces on the adjoining arm at the same corner (red dotted circle). If this occurs it would be reasonable to expect this to happen on more than just one corner and most probably on all interior corners, as it seems your photograph illustrates. One thing that I've learned over the years to help alleviate this problem is to build up the problem area with a little more of the material that will be shrinking... sort of a reservoir of material reducing the stress levels on the direct corner. This can be done in the design stage to incorporate the addition as part of the overall design or can be designed so that it will be easy to eliminate after the form is removed from the mold. In regards to your cross... if I chose the latter solution, it would involve softening the sharp acute angle with a soft curve (gray lines in the following illustration) of additional clay before making the mold. As you already have your mold cast, it would involve the careful carving away of plaster on those interior angles to produce soft curves, leaving possibly 1/8" or thereabouts of the acute corner still showing on the design face of the mold. This will give you a good reference then, for carving the added clay away from the area, resulting in the interior acute angles that you desire... once the cross is pulled from the mold... while the clay is still moist and easy to trim. And as Chris suggested, 'Your slip make-up, timing in the mold and drying times are crucial...' My outlined solution, should help eliminate some of the stress on the cross and possibly from you dealing with the problem, though it will involve a little more hands-on labor for each item cast... the trimming away of extra clay! I've seen many commercial molds that have included areas to be trimmed, etc., so it really isn't an alien idea in slip casting to do additional 'finish' work. Good luck!
  2. Ditto on the 'thanks' for pointing out the 'report button', John. Hadn't noticed that earlier. ......rick
  3. <br><br>Great post! It's very nice. Thank you so much for your post.<br><br><br><div> My intention is not to sideline the original poster's question and this topic...... but patrick198.... this forum is actually about ceramics and is really not a website that you should nonchalantly use just to slip in your "free online movies" link as you've done in both of your postings since signing up as a member this morning. A generic reply that you added at the end to simulate a ceramic member actually interested in what we have here such as ...."Great post! It's very nice. Thank you so much for your post" .... hardly makes it valid, in my thinking. With no disrespect for your business or desires to link us to watch"free online movies"... I would bet that you didn't even read what this posting was about! Am I wrong on this matter? Or is it O.K. for spammers to do that sort of thing here? Correct me, people, if I'm wrong here!
  4. An additional question to this particular use (of a pictured item created in 1181 A.D.) , in my mind, could also be... as the item could very well be an item owned by a museum ..... does the museum maintain any copyrights on the image? In years past, I have purchased 35mm photographic slides and postcards from museums that specifically has copyright information printed on the slide frames and on the postcards. An item created in 1181 A.D. (a very specific date from antiquity) to me certainly sounds like a museum item.
  5. Sorry...terraforma.... I wasn't using the uranium pentoxide in ceramics or glazing. I (as a grad student -1986) was given two pounds of the oxide by my instructor while at NYSCC (Alfred). He had used quite a bit on a large lead crystal sculpture in previous years, and this was his leftover. I used it to batch up 200 pounds of borosilicate glass for some sculpture work I was doing at the time. This is one of the pieces I was working on at the time. It traveled to Japan and then found its way to the Glasmuseum at Ebeltoft, Denmark, where it resides today. The bright yellow is the uranium pentoxide batched into a lead crystal glass and the darker green is the oxide batched into a borosilicate glass. Though it does register a little activity on a geiger counter, according to Corning Museum of Glass, it is a very low amount (less than one X-ray/year or something like that).
  6. Mushi... I've not personally used these particular rare earth metals with ceramics, but have used them (in addition to uranium pentoxide) in batch mixing of borosilicate glass. The results are breathtaking.... beautiful pastel colors with the addition of a wonderful color fluorescence under ultraviolet light. Can't help you with any recipe as such, but would certainly be interested in seeing photos/descriptions of any future testing/results that you achieve. Perchance starting with a translucent or opaque white base and adding in 2% increments up to about 8% could yield some nice pastels. If I recall I was utilizing about 2%-4% for most of my work in the borosilicate glass. Sorry I can't be of more help but it has been about 25 years since I was doing that work/experimentation and my memory has since faded in the particulars.
  7. Seasoned Warrior's picture of the scorp reminded me of the Skedkniv (spoon knife) that I sometimes use in my woodworking. They are traditionally used in carving for hollowing out forms ie, scooping out the interior of wooden clogs.... They are made here in Sweden by 'Mora of Sweden' and can be purchased online from Ragweed Forge.com (western New York)----- http://www.ragweedfo...ifeCatalog.html ----- They are sharpened on both sides and sell $20 for one or $35 for a pair. I've never tried them in ceramics but think I'll give it a try now!
  8. Hi Pat.... Sorry, I can't help you with your query..... but if you repost this in the Forum Clay and Glaze Technical, you may have better luck with more responses. ---rick
  9. Thanks Marcia, for that added input. Sounds like a technique I want to try in the near future. I've also been thinking about using reversed letter stamps that will give me a raised releif. Am presently in the middle of making the set of embossed letters for the stamps, but love your idea as well, for other styles of fonts. Rick
  10. The clay itself will not be as strong as it could/ should be. It will be more porous than a "stoneware" should be. Functionally it will absorb more water / liquid than a good stoneware should. In general fact, it will not exhibit the traits structurally that likely you are desiring in your change to "stoneware". The glaze will be seriously overfired if you take the body to the range it should be fired into ... cone 9-10. That will result at the LEAST in serious running. It may aslo cause some of the chemistry to "vaporize" out of the glaze (don't know the recipie or formula) thereby changing its composition. This will change the character of the glaze. It may end up looking like forzen 7-up soda... all fizzy and bubbly. Or with craters. Or with the color burned out. The list or potential issues is long. If you fire the glaze to cone 6 on the non-matured body 7-10 body, the bond at the clay/glaze interface layer will not really develop very much as it does in properly formulated stoneware. That decreases the stregnth of the overall piece as well as the strength of the glaze itself. The COE I already mentioned before likely will not match... and the glaze will likely craze. That crazing will further weaken the piece. Crazing will also let liquid through to the porous clay underneath, exacerbating any moisture issues. If the body absorbs moisture, use in something like a microwave will be problematic due to the moisture trapped in the clay even though the piece seems "dry". Repeated microwave use will cause the piece to crack. The piece will get dangerously hot in aq microwave. The list of potential issues is long. best, ............john I'm not much help in answering to your problem, savant, but thought maybe John could expand on this thought ... In trying to use this clay body (^7-10) with this glaze (^6), would it work and be a decent compatible 'fit' if the stoneware was fired to ^9-10 as bisque and then glazed and fired to ^6? I don't think it would be the normal approach but seems I've read that many ceramists do fire their items at a higher temp and often apply many (over/under?) glazes at lower temps as there is more diversity of brighter colors at the lower temperatures. That would mature the clay, but how will the glaze be affected for 'fit'? Possibly warming the ceramic a tad bit before glazing would help the glaze to go on the less porous matured clay, or would it not? ....Rick
  11. Not intentionally trying to hijack this thread but just felt it necessary to say..... John.... thank you for being such a vital part of this forum. Your answers seem so spot on, with the whole picture! Not to minimize your input either, Marcia, as I have gleaned much from you as well, and many others from this forum. I think this site has got to be one of the nicest places and most informative (media-wise) on the net. Highest of accolades to Sherman, et al, for putting this site together, and to all that continue to make this site the gem that it is! while I'm here (and hijacking...) I just recently picked up my new SKUTT 1027 (here in Sweden) but have yet to wire it up and fire it. I've many test tiles drying, in addition to the first batch of what will be hundreds of extruded border and accent tiles, all destined to finish my house renovation. The excitement runs rampant through my body and spirit in contemplation of that first firing. Meanwhile, I feel like a sponge, soaking up the years of experience, knowledge and wisdom from my ceramic arts gurus.... Interesting footnote to the SKUTT and electric kiln safety in general. Seems that nobody in this part of the world has ever heard of a downdraft ventilation system let alone the Orton EnviroVent®, including the suppliers. So I'll be forced to build my own electric fan downdraft system! Will probably save some serious kronor ($$$) in the process, to spend on more clay. But I just want to thank you wonderful people for being so giving with your all of your accrued experiences and knowledge. It is a such blessing for all of us (ceramic novice and otherwise) that you play an active role in this website! I now return you to the previously scheduled forum topic and discussion.... ..... Rick
  12. I would tend to agree with MudPotz about experimenting with melting the crush glass onto ceramics... with someone else's kiln. Because of the nature of the two materials, their expansion/contraction rates will no doubt be different, which implies that the end results will be cracked (if melted with thick areas). Some situations may have glass popping off the ceramic piece during heating/cooling ('annealing'-for glass) and hopefully they won't be stuck to the sides of something else or the elements or refractory walls. Glass tends to dissolve refractory over time. As Chris stated, at the lower temps (as cone 06 for non-lead glass) and depending also on what type of glass you are using (lead crystal, soda lime or borosilicate), the glass will tend to ball up. Increasing the temperature lowers the viscosity. Depending on numerous variables; ie, where they are placed on the ceramic piece, how thick, etc, firing/holding temperatures, they would give different results, some maybe favorable to your goals, some possibly disastrous to the hardware. If the glass chunks (cullet) is just crushed glass, there will be no volatilization of gasses unless you have added something to it (like soda ash, which is a flux for glasses). Indeed, interesting experiment Chris.....
  13. Yeh, Mea, I'd agree with that... I was thinking more in line with the fact that it was a 'good customer' coming back to purchase the item after you raised the price for him. Maybe that could also be looked at as a sign that you maybe could raise your prices!
  14. I suspect the short answer is there aren't any, but that's not entirely true depending on what you mean by "red". Since you brought up Mason Stains, which of their numbers do you consider to be the "true red" you're looking for? I would tend to agree azjoe. Wished I had a dollar for every time I heard someone ask 'is there a really good, true red?' That true red seems to be an elusive color when in the presence of high temperatures. Another aspect to this is also what azjoe is hinting at, in what your consideration is of a true red. I have actually heard three different people discussing whether a certain red color was the Christmas red of Santa's jacket. One thought so, the other's didn't. They each had there own idea of what THAT red was. Seems we all must have a certain perception of what that 'true red' is.... so much so that Coca-Cola even went to the expense of copywriting (patenting?) the red that they use on their products, (so I've heard). And I recall, years ago at a Contemporary Ceramics Convention in Houston, that one of the Studio owners asked the Duncan Product rep during his talk, this same question. I smiled and laughed inside when he responded, that Duncan 'was working on it, now, and thought they would have one out by the end of that year (1998)'. Haven't seen it yet! But then, I'm not so optimistic... feeling that with the thousands of years of ceramic history and the millions of people working within the medium in that time, that if it was possible it would already be on the shelves. Actually it is, it's called paint. And that true red paint doesn't need to go into the high temperature extremes which those reds seem to generally not be able to endure. Just my 2¢.... ----rick
  15. Ooooh! but to have more good customers like that!
  16. If the wet tile saw is equipped with a good diamond sawblade it should be able to cut it, however, the progress needs to be slow. Don't know what your sizes are (broken shelf and cutting table of the saw) but it sounds like a very safety risk operation. I had a diamond saw for years that I used to cut many different stone hardnesses and a lot of my 10" thick cast borosilicate glass. Some shelves are also very very hard, don't know what the mohs hardness is of the different compositions of shelves, but I believe carborundum is about a 9 on the scale of 10 (diamond). Still, I probably wouldn't attempt it as diamond blades are expensive to replace!
  17. Amen! best, .......................john Ditto from me on that point, as well... Rick
  18. KathyG... after rereading your post, an addendum to my previous response above would be that it doesn't sound like it's that much extra space. The bricks will expand and contract naturally anyway as they go through the regular heat up and down cycles. One/quarter of an inch is not enough to personally bother me, but that is a call that you need to make. The Fiberfrax I mentioned, however, does come in about a quarter inch thickness so could easily be added for the fill you need. I don't think I personally would spend the money for that additional amount, as the space age insulation blankets and felt papers can be expensive.
  19. I really don't believe it would be a problem as the air space (sealed off) is an insulating element unto its own. However any future problems would most likely occur (in regards to that design aspect) if something was bumped up against the sheet metal exterior wall hard enough to move the bricks inward. It would not be advisable to move the kiln either, if it is built on wheels, unless done so with absolute care, so as not to jostle the exterior wall or knock the kaowool loose. You might also care to check with your refractory supplier, they may sell Fiberfrax or some other insulation that would be suitable for the heat range with the thickness of the extra space you wish to fill. It will add to the cost but make the kiln more solid and could provide the (small) added benefit of extra fuel savings.
  20. Kathy... I'm not quite sure what your meaning is when you say 'increasing the Kaowool thickness from 1/2" to 1", as long as it can be compressed.' Kaowool like any other insulating product yields its efficiency in insulating properties when uncompressed. When compressed these properties are diminished. So if you are increasing your Kaowool blanket thickness, say, from 1/2" to 1" and then compressing back to 1/2" you would not be achieving much, if any, gain in insulation....In reality, you might be 'padding' the billfold of the supplier more than that of your kiln....
  21. Spotify is great to listen to as well.... one can find a style of music and listen the whole day to various artists or the same artist.
  22. I'm originally from E. Oregon, later lived in Eugene & Portland, prior to moving to Florida and then (now) Sweden. I recall there was a glass studio of hot glass near Bandon, if I'm not mistaken (read about it in the paper). Was that you? Love the cheese, as well...lol
  23. Your welcome, wish you luck on your endeavor. P.S. is 'bandonart' as in Bandon, Oregon?
  24. My two cents, from the background of glass artist to ceramics. Overhead elements are not really that important if you are utilizing warm-casting techniques (using plaster molds within the kiln). If your emphasis is on fusing and slumping then the overhead elements are more critical to the success of the work, without the sheets of glass cracking (from areas of different heat rates - center to edge of the sheets). This is most critical for larger sheets of glass as small jewelry projects (earrings, brooches,etc) generally aren't as susceptible to these thermal stresses upon heat-up. Many years ago, I purchased a SKUTT 818 porcelain kiln (cone 10) with just a kiln sitter and purchased a digital controller the kiln plugged into. I used this for 'annealor investment casting' of glass pieces as thick as 3"-4", with nary a problem. Next month I'll be purchasing a SKUTT 1227 for initial ceramic work, but I know in the future, I'll be using it again for glass casting as well.
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