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  1. Like
    tinypieces got a reaction from Rae Reich in Not sure why the glaze did what it did   
    Thank you all so much. I do not have any knowledge or experience with the chemistry of clay and glazes so I appreciate  what you're sharing!
    Benzine, I wonder what you mean by contaminated... the clay? the underglaze? the clear glaze?
    Bill Kielb,  I've taken a few more close ups. They may not be the same exact spots you indicated on your photo. I'm not sure you can see much more and I can't seem to get any closer.
    Neil, the edges of the bare spots are definitely not sharp, they are more rounded.
    liambsaw, youare speaking a foreign language! I sorry, I don't think I know what a stained slip is or an engobe and you completely lost me on the flocculated and Fishsauce slip,  haha.  Although I am really curious it being a lot cheaper than underglaze. Too, I prefer to incise the lines vs raised.

  2. Like
    tinypieces reacted to Pres in Looking for a template for round, wide mug   
    Hi Nancy, You may find some help here, if you start with a cone template and add a circle end to it. Look at the site, I can answer questions if you don't understand all of it.
  3. Like
    tinypieces reacted to neilestrick in Not sure why the glaze did what it did   
    Based on the close-up photo, those edges look pretty crisp to me. In crawling, the glaze pulls away from the clay and globs up around the edges, and I'm not seeing that. I usually equate shivering with the glaze coming off after the firing, but in this case it looks like it popped off earlier in the firing, because it appears to have melted into the glaze, which wouldn't happen if it was popping off after the glaze had hardened. As Bill said, it may be a moisture thing. How long do let the underglaze dry before applying the clear glaze? Do you let the pieces dry completely before putting them in the kiln for the glaze firing?
  4. Like
    tinypieces reacted to Bill Kielb in Not sure why the glaze did what it did   
    Since this is all speculation I would start ruling out things. My first would be thoroughly drying these with a really good preheat just below 200 degrees just to be sure that trapped moisture regardless of how minuscule did not cause this to burst early on leaving particles in the immediate area.  After the preheat,  I think I would stop the kiln and inspect. You could always throw these in an oven for an hour or two at about 175 degees. If you are brave there is the microwave which if cycled in small  steps would reveal the moisture as localized heating.
    My feeling is, this visual evidence is significant. In my lab I would put them in an evacuation chamber and pull the atmosphere down to 30 microns which would eliminate all possible moisture.  You are not gonna do that. My next thought is (already dry) I would put it in front of a fan, scan it with my infrared camera and see if there are obvious spots that have cooled. Very efffective way to detect moisture evaporating. Again, you are not likely gonna do that.
    my last thought would be to take a sample one and gently go around it with a torch to see if I could make a spot or two eject. As you can tell I am seeking the real answer. Most folks would likely do the long preheat and hope that it is indicative for future firings.
  5. Like
    tinypieces reacted to Min in Not sure why the glaze did what it did   
    I'ld go back to basics, try the underglaze alone, no glaze, and bisque fire it on.  Run 2 tests simultaneously, underglaze on green ware and on bisque. Bisque fire them both with no glaze and see if it stays attached to the clay. After bisquing try tapping the underglaze with a knife handle, see if any flakes off. Put the underglaze on with 3 thicknesses, 1 coat, 2 and 3. 
  6. Like
    tinypieces reacted to hitchmss in Not sure why the glaze did what it did   
    @tinypieces if you want you can use the @ symbol in front of a forum member's name and it will allow you to "link" or notify them that you are directing a comment towards them.
    I regards to whether or not its shivering or crawling, even if the edges are rounded, leaning towards a crawling issue, it might not be as easy as that to deduce. It could be shivering off (the opposite of crawling) and just melting into a rounded shape in the clear glaze you fired. Because its a "flat" surface, it would easily melt into the clear glaze and give the appearance of crawling.
    Id think that if you were having a "fit" issue (shivering/crawling), we'd see the same result almost everywhere. Whereas its sporadic; Im wondering if you are applying numerous coats of this underglaze, and you have thinned it down, that there may be TOO much water in your second/third coats, which are loosening(clay "ridges" become saturated with water, which decreases the "suck" that porous bisque has to wet glazes) the physical bond the first layer has with your clay. Then, either when the clear glaze is applied over top, you arent seeing the underglaze being "brushed" around, or it is peeling away, like crawling (even though its technically not a "fit" issue) in the firing, and melting into your clear.
  7. Like
    tinypieces reacted to Babs in Repairing greenware   
    Spooze does work but dont uese on handles  on mugs etc
    For less shrinkage i use paper added to spooze.
    Make sure the join is totally dry before bisquing, can sand iff roughness prior to firing.
    May have better results rebisquing prior to glaze fire
    If unfired piece is totally dry, can spray or zponge to redampen area .
  8. Like
    tinypieces reacted to oldlady in Repairing greenware   
    tiny, if the broken part and the pot have only separated with a jagged edge, you might try to repair it.  BUT only if the broken part is very small.   to try it, put the two  bone dry pieces together and support the pot with a nest of towels or some other thing so the broken part is straight above, vertically perfectly above the pot.  
    here is the magic that might work.  take a paint brush, at least a number 6 round camelhair or sable brush full of water and touch it to the very top of the broken part.   let the water run onto the piece and the pot so that the break is visibly wet.    then walk away for at least 24 hours.   do not touch it until you can see that the entire thing is absolutely dry.   
    it might work.     if it does not, you have learned to toss something that breaks.
    BTW, this is a good way to add sprigs or other decorative  additions .
  9. Like
    tinypieces reacted to hitchmss in Not sure why the glaze did what it did   
    slips are basically clay bodies (like what you work with) in a suspension of water. I.e. thinned down, kind of like reclaim. Fishsauce is just a recipe, just like there are different clay bodies. A slip is designed to go onto leather hard or wetter/softer works; engobes are slips that are designed to go onto bone dry, or bisqueware. A stained slip is just a slip with color(ants) mixed into it. The best black Liam mentioned is a "color" mixed by the Mason Company, who makes Mason Stains.
    Flocculated is a little more complex, but essentially a flocculant is a material which causes the particles to clump together, like a FLOCK of birds. A deflocculant causes the particles to repel each other. Not sure about Liam's flocculated slips, but I use a deflocculated slip, which basically makes the water wetter, which means it will shrink less, which provides a number of benefits. A flocculated slip would be one that would benefit in the attaching of handles; a vinegar(flocculant) slip will help increase the bond between attachments.
    Its much cheaper than underglazes because YOU would be mixing the materials together, instead of paying a company to basically do the same thing. Its not rocket science, kind of like baking a cake. Does require some precautions regarding the dust and the dangers of working with raw materials (and colorants more specifically), but easily done. It also means you can mix "custom" colors that a manufacturer may not offer.
  10. Like
    tinypieces reacted to Bill Kielb in Not sure why the glaze did what it did   
    Looking at these pictures it looks like the underglaze was ejected from the location. At each of these sites I can see residual underglaze adjacent to the decoration so something made this pop off prior to the melt.
    My guess at this point is trapped moisture or air that when heated, literally made these spots delaminate and land nearby in the base glaze.  
  11. Like
    tinypieces reacted to Min in Not sure why the glaze did what it did   
    If you put  underglaze on too thick or use multiple layers and don't allow each layer to dry before putting the next layer on the underglaze can lift from the pot. Looks like this is happening on the spoke shaped lines and the short lines, is this what you are referring to? I've only ever had one underglaze shiver but that's another possibility. 
  12. Like
    tinypieces reacted to Benzine in Not sure why the glaze did what it did   
    I've had a couple underglazes shiver, or otherwise come off the ware.  However, I don't know if it was an issue with the underglaze, or possibly a contaminated surface. 
    It's very rare that I've had it happen.
  13. Like
    tinypieces reacted to Bill Kielb in Not sure why the glaze did what it did   
    this is lowfire clear to 06 so it should melt over anything. Your picture really looks like the glaze shivered off in several areas but maybe more revealing is the minor amount of black underglaze scattered around these areas. The glaze and some of the underglaze appears to have been ejected locally before this melted which likely means the underglaze popped off early in the firing.  I would love to see a close up (in focus) of a couple of these spots. If you have a tripod or very steady hand and good lighting you likely could zoom in with your phone and get some detail. Of course the whole mail it to yourself thing might be necessary. In the picture below, the areas circled may be most revealing.

  14. Like
    tinypieces reacted to neilestrick in Not sure why the glaze did what it did   
    Is it shivering or crawling? Are the edges of the bare spots sharp like it flaked off (shivering), or rounded like it pulled away (crawling)?
  15. Like
    tinypieces reacted to Rockhopper in Repairing greenware   
    In addition to "spooze" (mentione above) - there's a commercial product called APT-II (apt2products.com) that's sold for this sort of thing - but, as they say "results may vary".  I've only tried it once - and it the piece still separated during the bisque firing.
    Depending on the size & shape of the brake, you may be able to  smooth the edges with a damp sponge, then take some similarly sized additional 'bites' out around the rim, and smooth them as well,  to make it look like an intentional design element.  (Lots of folks are into  'modified' pottery)
  16. Like
    tinypieces reacted to Callie Beller Diesel in Repairing greenware   
    Congratulaions! You now have a most excellent test tile. 
  17. Like
    tinypieces reacted to shawnhar in Repairing greenware   
    Same here, I've gotten a couple of leather hard pieces to attach, and some not, but once they are fully dry, none of them stuck.
  18. Like
    tinypieces reacted to liambesaw in Repairing greenware   
    Look up spooze, it can work sometimes, but on leather hard mostly.  Bone dry is not worth it at all in my opinion, the clay has already shrunk so far that adding anything wet to it will shrink out of the way again, so you might repair the same crack multiple times over the course of a week and still have it crack in the bisque firing.  On an elaborate sculpture you've been working on for weeks it's worth it... On a dish you can throw again in a few minutes, not worth it at all
  19. Like
    tinypieces reacted to shawnhar in Repairing greenware   
    Hate it so much! Just broke another handle on a bone dry mug yesterday, it was on my bisqued shelf and I grabbed it by the handle to load it in the kiln, whoops!
  20. Like
    tinypieces reacted to JohnnyK in Repairing greenware   
    Just last week I picked up a leather hard bowl by the edge and broke a piece off. my choices were: trash it; trim it down to half its size: or break the rest of the edge of the bowl and call it art. I chose the last option. For grins, I'm going to Raku glaze and fire it and see who might be willing to buy it as a piece of art. 
  21. Like
    tinypieces reacted to Pres in Repairing greenware   
    Time better spent making a new piece than putting in the time to fix the old one.
  22. Like
    tinypieces reacted to Mark C. in Repairing greenware   
    Make a new one and move on is the best way to fix this problem
  23. Like
    tinypieces reacted to liambesaw in Repairing greenware   
    Nothing worth trying in my opinion
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