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Everything posted by andros

  1. Dear all Hope this is the correct place for such a question… Recently I started to use for the first time some colored glazes (before I’ve always used uderglazes+clear glaze, cone 07. Never a problem). I've bought some commercial ready-to-use liquid glazes (cone 08-07 ) by an Italian producer (Colorobbia, line HSC). I know that those glazes are intended primarily for hobbyists and schools, so they should be quite forgiving, and is pretty viscous so its certainly added with CMC or something else to be applied with a brush... I did some tests with small objects like beads and pendants for necklaces but unfortunately some colors give always some defect... basically they “crawl” in some zones and make some pin hole...! I know that it could be due to excessive thickness of glaze, but otherwise for some colors it happen also with thin layers and others (if the thickness is smaller) have an inhomogeneous texture, they do not spread well… this is pretty odd because some other colors have never given problems… being all part of the same line I suppose that the basic composition is always the same, and only change the stain. There’s certainly something that I’m doing wrong but sincerely I don’t know what… !!! Somebody could have any idea?
  2. Glaze issue

    Finally I've done it! I have applied a couple of your suggestions: thinner glaze layers, no sanding, clean with water and soap (not only water) and work with gloves. And finally I've succeeded in obtain a decent result! (neglect the one on left-bottom, it's a failed test with underglazes...) Thank you again for your suggestions!
  3. learning to use underglaze

    If, as I belive, CMC is the acronym of Carboxymethyl cellulose, then it is available in any... shop specialized in supplies for pastry! I have already used it for some glazes, but the first time I bought it to make sugar paste icing for a cake... If I have understood something I'm going to add both CMC and a little bit of bentonite (no way to get VeeGum-T ) as a surface hardener (to allow to put more layers without the one below is spoiled). Thank for the tips!
  4. learning to use underglaze

    I have underglazes. At a first I got confused because of the deeply different approach to undergalzes between Italy and US. I never thought that they could be used in any other way but as watercolors, and seeing how it was used many times in the US I thought that they must be two different things, but actually they are not! The only difference is that italian uderglazes are not intended to be used in "the pure form" but only very thinned, as watercolors, so they are in the form of powder (and therefore it does not have any type of thickener or suspending agent) or in the liquid form, but with the wording : "concentrated color, to be thinned with water before use", so they probably have only suspending agent, but nothing that helps brushability or to harden the surface. The main Italian supplier is Colorobbia: http://www.colorobbiart.it/catalogue/?lang=en
  5. learning to use underglaze

    I think that this is what I'm looking for! Actually I don't know the exact composition of my commercial powder underglazes but I think that it doesn't differ a lot from an US underglaze... Unfortuatelly I'm not able to find it in my region... VeeGum-T appears to be a commercial name for smectite clay, that is a very generic name that comprises many different clays... Could bentonite act at the same way?
  6. learning to use underglaze

    Some days ago I noticed to have in my my inventory some Duncan underglazes... I had not used them for so long time that I forgot to have them! I have always used them very diluted as watercolors. With them I made some tests and actually I noticed that they are different from italian underglazes not for the composition of the color itself but just because they (duncan) are problably added with some sort of gum to meke them "brushable" and to form a compact layer. I tried also some italian liquid underglazes and although they don't form a compact layer like Duncan underglazes, it's still feasible to use them like "US underglazes", the only problem is that they are sold in very very small jars (less than 1oz) and to use them in the "pure form" make them definitely not cost effective... In my inventory I have also many jars full of powder undergalzes. I tried to use them to make solid layers but is unuseful to say that is not possible because once dried they return to be powdery and is not possibile to make multiple layers. Does anybody know what I can add to powder underglazes in order to make them brushable and to form a compact layer? Maybe some CMC or other? Of some colors I have some lbs (a lifetime supply if used as watercolors!) and I think it's worth trying to use them like "US underglazes".
  7. Hi folks! I've just been given to me what I hoped to be my first own electric kiln. It's a very very small stackable top loading kiln. The chamber is more or less a cube with 12"\13" (32cm) side. Microscopic but mine! Unfortunately it doesn't work... () because it's not able to go above 1300F (700°C)... It's too a small and old kiln to spend money to replace the heating elements, even because the control unit is very "primitive" so I would have very small control on temperature rising velocity ecc.. Just to not toss everything, I thought to convert it in a updraft raku kiln. It's a lot of time I've planned to build one raku kiln and I think that this can be a good occasion since I can save the cost of the isolating blanket. I'm little scared that the kiln will be just too small to have an evengas heating but at that point the cost of a barrel and a ceramic fiber blaket will be not so high... I read a ton of threads here and elseware but just I couldn't find out an indication on what the diameter of inlet and oulet should be... I will use a weed burner with a torch diameter of 6cm so I thought to make both the inlet (in the bottom) and outlet (in the lid) of 8cm... I need to buy and use a hole saw (and I want to retain the "scrap") so I want to be pretty sure that I'm not going to enlarge it because are too small... I'm going to put a cordierite"flame spreader" 5cm high above the inlet hole. Somebody could give me some tip or tell me if this stuff will never work properly??
  8. Umpteenth question on raku kilns

    Thank you for the reply! In order to ensure enough air moving iside the tiny chamber do you think that some sort of chimney will help? I'm going to keep the control unit, not indeed to control the heating elements (that has already been cut off) but because I need the reading of pyrometer (that probably will be pretty out of calibration but I can compensate it with some try with cones) so I could do without the possibility of peeking through the chimneyf... And anyway i could do some sort of peephole... This is just a temporary solution anyway... In a (I hope not too far) future I will replace it with abigger ceramic fiber chamber... is someone albe to figure out what is the maximum volume heatable with a weed burner with a nominal power of 80 KW (about 273.000 BTU?)
  9. Getting zinged by bisque

    Here I can see no clue... Corundum is just aluminum oxide "doped" with other elements that give its color (in the case of the involved stain appears to be manganese)... sometimes corundum crystalline lattice can be tensioned and cracks because of big doping elements (i.e. chromium in ruby, and this is why it's so rare to have big rubies) but this is likely to happen only in big mono-crystals, and in this case, In my opinion, there is no explaination in the composition of the stain. Some foreign element\agent should be involved...
  10. Getting zinged by bisque

    So weird... Looks like a kind of blistering... the behavior almost seems to suggest the presence of particles reactive to the water, like burnt lime (from calcium carbonate). This defect (even if not always is a defect) can occour in some clays for bricks, roof tiles and other outdoor objects. But hardly I can see this in a stain...
  11. I never made objects that are intended to contact with food, like tableware. But since I'm planning both to expand my production range than upscaling a little bit my tiny buisiness, I've been hitted by some posts that rightly mention "food safe regulation"... Since I live in Europe and regulations could differ a lot from US and EU I only hope that some Europeans that read could help me, because I don't know who knows anything about this matter and, being a non-professional, I can't ask for informations to craftsmen associations... On-line material is unuseful. My understanding is that is not not enough to use materials (clays, glazes) that are stated to be "food safe" or lead free glazes and so on... In addition my understanding is that the (tableware) producer must draw up and keep some documentation that demonstrates how he has made sure that his products are food safe. Also some "releasing tests" appears to be involved... Really to make and sell a couple mugs (maybe an hoobyist like me that sells sometime is some small country fair) does is needed all this procedure?
  12. Page 31 appears suggest that potters should perform testing only if they use problematic materials... this is very reasonable, but I do not find evidence in the legislation...
  13. I read online also some rumors (also from Higher Institute of Health members! This in some presentation made for ceramic industry) obut a revision of the directive itself... At least here the result of such a things is that nobody does nothing waiting futher developments... Anyway if something of more detailed for artisanal pottery will follow, for me is well accepted! Anyway a lot of very interesting and useful stuff from all of you!
  14. I think that this due to the fact that the aim of the EU document was primarily to "develop adequate methodologies for testing these articles" insted of make a methodic study about how metal leach s changes as the boundary conditions change... this is something that can be interesting for us (and in this way I will find much more time to study the interesting material posted by @Min. It's the potter that should be interested on how to avoid excessive metals leach. It is sufficient for the legislator to set thresholds that make sense ... isn't it?
  15. Handy Techniques

    The kitchen is my primary source of tools, as for many other people. A wire cake cutter is far more useful as a clay cuter. Pastry rings can be fine to make clay disks. A sturdy aluminium syringe for biscuits is my favorite portable small extruder... needless to talk about the wooden rolling pin ...
  16. One thing is not so crear to me... maybe because I'm little dummy or I paid insufficient attention, but...(I'm referring to the test report found by @High Bridge Pottery Pottery) Hollow articles appeared to be tested in the interior, i.e. they are filled with acetic acid or another test liquid ("The articles were filled with the test liquid to a level no more than 1 mm from the overflow point"). But at p19 also the external surface appears bitten... This is something that is not so clear (to me) also in the EU directives. Do only the internal parts that are destined to contact food need to be tested? Could I (for example) make a mug externaly lead plated but with a safe glaze inside? Another thing... should I test every single shape I'm going to make? Does is not sufficient to test the couple clay-glaze fired at a given temperature? I don't think that there is significant difference between a mug or a bowl if produced with the same clay and same glaze...
  17. I've just read an interesting article (titled "Detailed and Unstructured", Witten by Lori Martin) in Pottery Making illustrated from the Jan/Feb 2018 issue. I find this technique interesting and similar to another technique that I love: cuerda seca... I've just only a couple of doubts... First: does really is possible to apply a colored glaze over a clear glaze (2 coats!) without have the colored glaze leaked\blended? Should I take some precaution in order to avoid problems? It's not the first time I see somebody who does such a "design", but everyone else did not put anything "in the background"... Second: What kind of colored glazes could be used for that job? Expecially for the black outlines... they does not appears as normal "glassy" glazes... The only american brand easily available in my area is Mayco, and I've noticed that some glazes like "stroke & coat" are pretty different from glazes I was used to use...
  18. That's something! The only Italian Language pottery forum I know is technically dead... it's not a case that I'm writing in a forum that is intended to be international but is basically US born... This is also my impression (only an impression, I admit) for Italy... This is very interesting! It would be a very precious thing to have a firsthand witness about how it does actually works! I don't think that in this case there will be deep differences between Italy and France ... Let me know, please!
  19. I'm sorry, my comment were intended only as a joke. I would never want to go into this speech first. This in general, much less here... Anyway I admit that my post was very (maybe to much) controversial with the law, but only with the fact that it looks to be very disheartening for small craft potters. Nothing to complain with the right necessity to protect people from poisoning (and in this way I also appreciate the intent of the law) but personally I'm only discouraged of not being able to understand how I could be compliant with the law in my case (and I think in the case of many craft potters) or at least by the fact that it appears so complicated, and I'm afraid I cannot have the resources to be compliant. This not exactly because of the law itself, but (mostly) because are missing easily available clarifications and clear explanations about the real practical impact. Anyway once uderstood what I have to do, and how, and once understood that it's not so complicated as it appears at first glance, I wuold very happy to be compliant... and yes, I would feel even better too, because I would be 100% sure to offer a safe product, given that I give it especially to my friends... For once, Italy has adopted the directive without distorting it! The Italian decrees are a copy and paste of the directives ...
  20. I'm convinced of the fact that all Americans who read these things will find all very odd... Because all this stuff is very very European!! So bizarre, convoluted and complicated ... I've just taken a look at the huge maount of directives and decrees (3 EU regulations, 2 EU directives and 2 Italian Ministerial Decrees!!)... In Italy the situation seems to be the same as France. Unlike UK I have found no trace of any guidance, memorandum, and something else that mentions "craft potters and one-man operations"... Incredibly I can't found any comment or post in any forum or other... this is very strange because in Italy is full of craft potters (not in my city!) and I can't believe that nobody is concerned about all this mess... The absurd thing is that everything appear to have been thought only for industries, because it's true that is told that everything must be scaled in order to avoid excessive burden for small companies, but at the same time the directives appears to require some "management system" in order to ensure traceability of materials... So, should craft potters be certified ISO 9001?!?!?? Probably not, but... The most absurd thing anyway for me is the fact that everywhere is mentioned the "company". It is given for granted that the pottery "producer" is a "company". Also a one-man operation is a company and this is ok... but what about people like me that are allowed to partecipate to some country fair and sell something on occasional basis without having a VAT number? For my little and negligible business I don't need to be enrolled in the "chamber of commerce" and I don't need to have a "company"... Does all this regulations and decrees apply also to me ot not? If yes (and I think it is) how it applies to me?(I don't expect that somebody answers to those questions...) As always, when it comes to dealing with the EU\Italian law, the mystery deepens ...!!! Two things for @Sputty... First: I find that clarification in English by far more understandable that italian political jargon!! Second: I think that UK potters will comment "let's go with Brexit!!"
  21. Damn, what a mess! Thank you al lot @Sputty... it will take a lot of time to find the courage to face all this legislation!! Probably in a few weeks I'll ask you for more clarifications ... but not before!
  22. For majolica I used a normal white glaze (not tin glaze) and everithing was ok... as I told in another post I aways applied one coat of underglaze pretty diluted, according to italian tradition. In this way colors don't appear "solid" and uniform like those applied with multiple layers but anyway they appear bright... Anyway I understand that normal underglazes and stains used over a white glaze (tin or not) don't have usually enough flux, so it's necessary apply at least a thin layer of clear glaze as a finishing coat. Of course this layer should be applied by dipping or sprying because brushing would rub out the colors... Maybe this can be the reason for your pale colors? For majolica exists colors made expecially for that (called "overglazes") with more fluxes, but also many majolica artists in Italy uses underglazes with that precaution, so they are not forced to have may different kind of colors...
  23. Mug dimensions

    Unfortunately I'm not able to be helpful for you, but thank you for have forgiven my open to misinterpretation words! Have beautiful holiday you too!
  24. learning to use underglaze

    @oldlady and @Roberta12, , thank you for your help...! Simply in these days I'm getting so confused... I sow so many new techniques (that in US are pretty usual but in italy are not) that I do not know what to think anymore! As I told I used underglazes for at least a decade but always as a "watercolor" according to italian tradition, duliuted, because... I was taught this way! Now I see a deeply different way to use that and I wondering if are even another thing... I don't know... maybe italian underglazes has less clay content or more stain content... I saw some underglazes (US) recipes but but in Italy those recipes doesn't exist. Exists only commercial underglazes so I don't have a comparison. I know that the ingredients are the same as US undergales but I don't know the proportions. Moreover in Italy there is a website that sells pottery materials and it's the almost the only one that sells one american brand (Mayco). I tried some glazes like jungle gems and stroke and coat. Those products was really good and pretty different form italian products. They have also mayco undergalzes but the descrpition of those underglazes is enigmatic and ambiguous (this site wirte "undergazes-engobes"!!)... I want to buy some pieces to try if they are really different but so near to Christmas I need to wait some days before to get them! Moreover I want to use my italian underglazes with the US manner... I'm so impatient to do this! But now my tiny studio is so crowded with other stuff that i would combine a disaster! After holiday period I will try and (hoping not to bore you) I will let you know the results!

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