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Cadaola

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About Cadaola

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  1. What Is Wrong With This Recipe?

    In my test tiles the glaze behave nicely. I suspect clay, carbon material and glaze firing too fast being guilty, so I will try to bisque and glaze fire differently. I think that if the problem is carbon material not burned away I should have the same problem also with other glazes that istead work properly, even if it is true that sometimes I have a small crawl problems with a transparent glaze... I will let you know. If you like the result and want to use this glaze, in my test tile I obtained a blue I really like by adding 2% manganese, 0.4% chrome ox. and 5% rutile. (I post a picture) I did not try it yet on pots, so I don't know how it will behave... All the best! Paola
  2. Glaze Squirt On Kiln Shelves

    I received a lot of input from all of you and I'll try to find my way. I will let you know about my results (hoping they are positive). It will take a while (maybe months) but I will tell you for sure! Thank you for your support and help! Best wishes! Paola
  3. Glaze Squirt On Kiln Shelves

    I think you should rethink about your firing schedules for bisque and glaze. 85C is quite fast for the last step of glaze firing and if you are going this fast than the top temperature should have been 1230 C, but since you hold it for 15 min than the top temp is 1221 C Also depending on how good the elements are it is possible that the kiln can't fire this fast. Do you use self standing cones, or make your own cone pack? David I took the glaze firing schedule from digitalfire: http://digitalfire.com/4sight/firingschedule/mastering_glazes_cone_6_firing_schedule_83.html I usually use a more simple firing schedule: GLAZE: 120°C (248F) /h to 600°C (1112F) 135°C (275F) /h to 1230°C (2246F), soak 30 min. I have an electric kiln. which firing schedule do you use or recommend me to use? (I don't use cones, because the kiln seller told me they are not useful because the kiln is high performance and fires very precisely with the same temp all inside... but I will buy them now, that I understand I can reach cone 6 without necessarly reaching 1230°C (did I understand correectly?) Thank you :-)
  4. What Is Wrong With This Recipe?

    http://www.sciencedirect.com/science/article/pii/S0032591004001196 ...and this one.
  5. What Is Wrong With This Recipe?

    http://www.sciencedirect.com/science/article/pii/089268759500030T I found this article about calcinating colemanite...
  6. What Is Wrong With This Recipe?

    I am in europe but not at home in these days... i realize looking back at the recipe that i forgot to mention the coloring oxides i actually used for glazing the pot and that may affect the final result... In the base recipe i added 0.4% chrome oxide 5% tin and 6% rutile. Thank you David for your tests! I will read your post carefully when i an back home trying to understand... It is possibile that when i substituted colemanite with Frit and i had the spitting problem, it was caused by thick application... Because i am discovering now that i tend generally to do so and only recently i am correcting this bad attitude. Rayaldridge, you did not misunderstand me.
  7. What Is Wrong With This Recipe?

    "When I said that about firing too fast, I meant in the glaze firing." Probably true... "What does the glaze look like after application, but before firing? Does it have a lot of little cracks?" No cracks. "Maybe the glaze is too fluid, but the pattern in the last picture doesn't resemble what happens when a too-fluid glaze runs off a pot. Usually if that happens, the pot is firmly attached to a big puddle of glaze. That looks to me like the glaze fell off the pot in little chunks and collected around the pot, before it melted." Because I had several times spitting problems I don't trust my glazes and when I suspect a glaze (boron glaze are among the most suspected!) I put the pot on a ring to elevate it from kiln shelf and avoid to stick to it. "The blobs of glaze on the shelf are standing up pretty high." True! "It's an intriguing problem, but it must be very frustrating for Paola." I agreeeeeeee
  8. What Is Wrong With This Recipe?

    True: the problem in that case was actually the thickness of application. I solved the problem with tenmoku+chun blue and blu-green matt glazes by thinnig the layers, I fired then in the same kiln of the recipe of this topic (also same layer thickness), which on the contrary still give me problems...
  9. What Is Wrong With This Recipe?

    The reason for calcining clay is to reduce problems with glazes having high clay content from cracking after drying and chipping/falling off the wares before firing. Clay in the glaze shrinks as it dries. Calcined clay (EPK) will not shrink as much. Ok, now I know the difference between calcinating and fritting (maybe). I thought that calcinating and fritting was the same process: a kind of bisque firing of a material in order to give it better qualities. I mean by fritting you made less soluble a material (for example the boron) and now I know that by calcinating you eliminate extra water. I imagine that fritting needs a different and more complex process than calcinating and it is true, it is a pity, because I have plenty of colemanite and it would be perfect if I could simply transform it in a better material just by bisque firing!
  10. Shiver Or Crawling?

    How much flux would you recomend to add?
  11. Glaze Squirt On Kiln Shelves

    I refired the small object adding some glaze on the bare surface and it came out well (not perfect, but ok). I fired this second glaze kiln with a different curve in order to avoid the spitting problem and it worked well only in part: for the tenmoku-chun blue it worked well (no spit on the shelf) even if the surface quality changed a lot, but it is still pleasant (and I changed the temnoku glaze with an iron red glaze). (see small cup picture) I also changed application methods: I dipped or poured instead of brushing, and I added some water to the glaze in order to obtain a thinner layer of glaze on the pot. That was useful. I had a problem with another glaze (with boron content), but I already posted about it, so I don't say again here. Here the firing schedule: 55°C/h to 110°C hold 30 min 200°C/h to 1080°C no hold 85°C/h to 1200°C hold 15 min 275°C/h to 1000°C no hold 70°C/h to 760°c no hold and cool naturally
  12. Shiver Or Crawling?

    Actually sometimes it occurs over the green underglaze too Thanks for you suggestion I will try to add some flux. I also experimented a more bloaty effect if the underglaze is applied at a too dry stage of leatherhard. So I put it on at not too dry stage, but it works only sometiimes.
  13. Shiver Or Crawling?

    "In the last picture it looks like the underglaze isn't adhered to the pot and is lifting up during glaze firing." Exactly! I apply the commercial underglaze at leatherhard stage.
  14. Shiver Or Crawling?

    BISQUE: 60°C (140F) /h to 120°C (248F), soak 30 min. 100°C (212F) /h to 600°C (1112F) 80°C (176F) /h to 980°C (1796F), soak 30 min. I always clear my bisqued objects with compressed air and sponge them with just a little water. In this case I thin gun sprayed the glaze, and waited 2 days before firing. The green glaze is an underglaze already bisqued at the time I glazed over with the clear glaze. I am sorry, because of my poor english, I don't understand what you mean for water smoke... could you explain to me? Thank you!
  15. What Is Wrong With This Recipe?

    Does anyone has already tried to "calcinate" colemanite as Wyndham is suggesting me to do with EPK? Could it work? I really want to thank you all a lot for helping me, I live in a small town, I know some potters around the region, but none of them has interest in experimenting or sharing... they all buy commercial glazes because they don't want problems (and I don't blame them for that, sometimes I feel like I should do so too!), so I really am alone in my way and you are the ones who encourage me to go on and even understand my poor english :-D Your enthousiasm, competences and kindness are overwhelming. So thank you, with love, Paola
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