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jo4550

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Everything posted by jo4550

  1. There is no reason why you shouldn't fire decals in a gas kiln. The main thing is to have a very slow temperature rise to 400-450.C so that all the combustibles can burn out. At all times keep the kiln in an oxidizing atmosphere to 800.c. You need to keep a clean atmosphere so even over-oxidiziing is advisable. For many years I fired both lustres and decals in my gas kiln very successfully. Johanna
  2. Duncan Gold Luster Question

    You may find that lustre on stoneware fires better at the higher end of the lustre firing 800-820.C. If you come across any books on lustre you will find that different firing temperatures are given for different categories of glazes. These categories are usually glass, earthenware, soft paste porcelain, hard paste porcelain. Stoneware falls within the hard paste porcelain range of firing temperatures whereas cone 6 glazes would fall within top end of soft paste porcelain. Lustre relies on bismuth oxide to flux or bind to the surface of the glaze. Johanna
  3. is gilding / gold leafing food safe ?

    The best way to remove purple spots is with a gold eraser.
  4. Duncan Gold Luster Question

    It doesn't matter what brand of gold or lustre you are using you should not be present in the same space as the kiln when you are firing these. The toxicity of gold fumes is present till at least 450.C. You will notice that is when the smell also disappears. You should never work in the same space as a kiln when it is being fired. Fumes are being emitted all the time.
  5. Silver Lustre

    Silver lustre tarnishes. Nowadays industry uses platinum lustre instead as it does not tarnish.
  6. Decal Help Please!

    Stephen, ceramic toners will not work in a conventional laser printer. The printer needs to be altered to accommodate the use of the ceramic toners. I believe some Ricoh printers are retrofitted for this. The polymers (plastic bead like substances) adhere the colours to the decal paper. Mason stains are not milled fine enough for laser toners and they need to be mixed in specific proportion with the polymers. There are also 2 different systems out for ceramic toners. One has a flux in the toner mix which allows the decal has at approx 800.C. The other has a flux in the covercoat which is applied after the printing. This allows the decal to be fired at the temp required, eg for glass, overglaze or inglaze temps. Regards Johanna
  7. Decal Help Please!

    To determine compatibility with laser printers, look up the MSDS sheet for the toner cartridge the specific model uses. Some laser printers use polymers as the main pigment ingredient. These won't work. Others use iron, listed as ingredients beginning with the prefix "ferr." This what to look for. The HP I have uses 45% iron in the toner pigment. As I understand it the polymers, when melted, are the binder of the colourant to the paper in laser printers. Originally carbon was used as the colourant for black and this is still used by most laser printer manufacturers. However HP definitely uses iron oxide (also written as ferrous/ ferrous/ferrite) for their MONO laser printers. To add to this, the reason a colour laser is not suitable, is that the printer drum has to go to a higher temperature to melt the polymers used for the other colours. This higher heat melts the laser decal paper onto the drum thus rendering the printer useless. Regards Johanna
  8. is gilding / gold leafing food safe ?

    Hello Kennedy It is normal for some glazes to change on a refire especially when you are approaching the softening point (I do not mean melting point) of the glaze. This is the point where the fluxes start to be active. This has become very obvious when running the laser decal classes and searching for the softening point for the decal to adhere. There is a fine line where the glaze doesn't react and this is at the lower end of the temp scale. I would hazard a guess that your glaze has a flux that has a very wide firing range and it is perhaps Gerstly Borate. You seem to have reached a point at cone 06 in your glaze where the glaze is already outgassing and the cooling at 06 halts the process and and traps the gases changing both the colour and the integrity of the glaze. To resurrect this glaze AND burn off the lustre find a cool spot in your glaze firing and take back up to top temp. This should restore the glaze. I say cool spot as refiring is almost like going a cone higher than the original firing. I would have attempted to save the gold and platinum surfaces by adding a couple more layers (with firings in between) and firing to your gold firing temperature before I took the drastic step of burning the lustre off. To remove small areas of lustre it is common to use a gold eraser but it has to be used carefully as you can "matte" the surface of the glaze that you are rubbing. Lustre can also be removed by using hydrofluoric acid but I personally wouldn't go down that path for H&S reasons. It also mattes the surface of the glaze where the lustre has been removed. Cheers Johanna
  9. There are a couple of issues here but I would like to start off by pasting an excerpt from the Heraeus fact sheet on Lustres as I have run out of space to add any more attachments. This can be found in its entirety at http://tinyurl.com/lvt6m7c Heraeus is one of the largest overglaze and lustre producers/suppliers in the world. They are based in Germany. 1 General Information Lustres are based on metallic compounds dissolved in organic solvents. After firing they form a very thin layer (less than 0.1 μm). Typical characteristics of lustres are their brilliance as well as their metallic iridescent brightness which occurs after firing on smooth substrates. The lustre loses its iridescent effect on matt surface and appears matt. Lustres are suitable for the decoration of glass, porcelain, bone china, earthenware 2 Firing Range 480-630° C / 896-1166° F for glass and lead-crystal. 650-900° C / 1202-1652° F for porcelain, bone china, earthenware and tiles. 3 Precious Metal Content Lustres contain less than 6 % precious metal or are precious metal free. 4 Properties 4.1. Mechanical Resistance The mechanical resistance of lustres does not achieve the same standard as most ceramic colours and precious metal preparations because the formed lustre film is very thin. Therefore, we recommend that customers test the decorations under their own conditions to achieve the required resistances. From this excerpt you will see that lustres applied to tiles used as a splash back may be a short term measure as constant cleaning with an abrasive will soon wear off the lustre. However I am assuming that you have taken this into consideration. I am finding it hard to get a good image of the tile to show that it has a creamy base so I cannot comment on how many firings this would have had but I suspect only one overglaze firing. As you can see from the excerpt lustre can be fired anywhere up to 650-900° C / 1202-1652° F depending on the surface it is on. The controlling factor is the softness of the glaze that it applied to at the temperature you are firing to. The softer the glaze becomes the more the lustre will sink in. This is especially so for low earthenware glazes. As I have said in previous posts Duncan products are rarely, if ever, used by the porcelain painters (the main users of Overglaze techniques). They buy products that are are manufactured by the suppliers and not just repackaged and rebranded as in the case of Duncan overglaze products. I have also never heard of lustres being described as Lustre Overglaze. Regarding Duncan's instructions that you supplied here are my thoughts. 1. Any glaze or surface is overglaze compatible. (I don't understand the need for this statement) 2. The firing temperature is suspect. Maybe it is a typo and it is meant to be cone 016. I don't know whether they are offering a normal lustre because lustres starts to burn off after 900.C and they state to fire to 1000.C I would normally recommend firing a cone 6 glaze to 760-780.C however I have refired them successfully to 810.C In your situation where you will need extra mechanical strength I would suggest you run a test and see how the cone 6 glaze interacts with the MOP at 900.C. It is a chore but you won't know until you try as each glaze behaves differently. The MOP that I use is a Fay Good product and can be purchased in the USA from China Painting today. Here is a direct link http://tinyurl.com/mg3ml75. #Ceramics Monthly January 2013 contains a techno file on Lustres #Pottery Making Illustrated May-June 2013 has an article on how to use lustres. Johanna DeMaine
  10. Here is a youtube link of an old Wedgwood 1930's film that shows you the sprigging process. Here is also a link to 2010 CAD archived feature on sprigging http://ceramicartsdaily.org/education/ceramic-art-lesson-plan-making-sprigs/ Johanna
  11. Hello Sue What you are describing is quite prevalent in refiring glazed ware at at China paint temperatures. It is often called mildew but it is actually black spotting that occurs on the UNGLAZED surfaces when the clay body has NOT been fired to full maturity. Hence you will normally find it under the work (where it touches the shelf)and footrings. It is not trapped carbon from poor bisqeing. It is mostly found in older pieces that have been around a while. It is carbon being trapped in the open pores of the body and this can be generated from a variety of sources. The carbon can become reabsorbed and trapped from the media being used so it is more prevalent to occur from oil based mediums than water based mediums. This coupled with poor circulation and ventilation in the kiln during firing allows the pores of the unglazed clay surfaces to reabsorb this new carbon. This carbon can be burnt out with repeated firings especially if the temperature is raised slightly higher. The easy answer to all this is that if you are making things from scratch make sure you fire to the full maturity of the clay or otherwise get a clay that vitrifies at the temperature you want to fire to. Then this problem shouldn't occur. Always make sure you have the lid or door of the kiln slightly ajar in the overglaze firing until at least 650.C This allows the gases generated from the mediums to be dispersed. Always allow plenty of space between the shelves in the kiln during an overglaze firing. Always try to fire to the highest temperature in your overglaze firing depending on your glaze type. eg if using porcelain fire to 800-820.C rather than the lower 760-780.C option. This allows more carbon to burn out. If at all possible fire your pieces lifted OFF the shelf by little wads or pins. I have attached a small .pdf made from page 125 of "Ceramic Faults and their remedies" by Harry Fraser. This deals with this topic in greater detail and it saves me from having to type it all out. Black spot.pdf Regards Johanna Black spot.pdf
  12. is gilding / gold leafing food safe ?

    Hi Kennedy You seem to be on the right track with your choice. Here is an extract from an article I wrote called "Health and Safety and Overglaze (in paticular lustres)" which is reprinted here on my website http://overglaze.dem...rg/?page_id=460 "My method of protection from fumes is as follows. I use a fume booth constructed by my husband together with a respirator while I have developed a method of working that limits my exposure to the hazards involved. I use a resist method whereby I estimate that 90% of my time is spent using lustre resist which is quite inert. The other 10% is the actual application of the lustre, as all the fine lines apart from some gold pen work is achieved by resist. I am confident that I am limiting my exposure to lustre. As well as this I wear a respirator. It is a Norton brand 7700 series silicone half face mask model with 2 N7500-1 organic vapour cartridges. It is extremely comfortable to wear despite the fact that I wear glasses. These cartridges are not suitable for clay dust etc. For that you need a particulate filter. However it is not enough to just wear the respirator. It must be maintained. When you have finished using it the inside must be wiped and then the whole lot stored in a sealed (clip lock) bag). This extends the life of the cartridges and keeps dust out. The cartridges need to be replaced when fumes can be smelled through the respirator. Norton has recently been taken over by North Safety Products. A web link to view is http://www.westernsafety.com/newnorthrespirators/newnorth1.html" Regards Johanna
  13. is gilding / gold leafing food safe ?

    http://chinapaintingtoday.com/store Look under Precious metals. I can recommend the Fay Good 12% liquid bright gold. It is a German product. It is the one I use. Another link to gold is http://www.thegoodstuff.com/ghlb1.html. This is also a German product. Germany has a history of producing the best gold. Golds and lustres are best bought from China/Porcelain painting suppliers. I don't know of too many painters who use Duncan products. They are aimed more at the hobby market. Regards Johanna
  14. Glaze Problem on slipcast items

    Several questions spring to mind here. How are you glazing? Are you glazing the inside and outside separately and in what order. If so what is the drying time between the inside and the outside? Are you brushing on the glaze? Are you spraying the glaze? I ask these questions as it seems to me that you may have a problem with crawling (glaze pulling away from the surface during the firing). I have experienced this when dipping glazes on thinly constructed work. The bisque becomes saturated when more glaze has been added to a surface. Bubbles or blisters appear on the unfired glaze during drying. These can be smoothed back by rubbing. However in the majority of cases the glaze crawls during the firing because of the lack of adhesion of the glaze to the surface. With brush on glazes this can also occur when subsequent layers can lift off the first layer be it ever so slightly. With sprayed glazes this can also happen when too thick a layer is applied in one hit rather than several thinner layers. One way or another the bisque can becomes saturated. Saturated areas do not have good adhesion with the glaze. With reference to your statement "about 70% of the problem pots have the problem on the side facing the elements" it may be that the side facing the elements initially heats up at a more rapid rate than the rest of the pot and trapped moisture causes further problems with poor glaze adhesion. I note also that your bisque temperature is higher than your glaze temperature. Could this be contributing to the poor adhesion? Regards Johanna
  15. Australian substitute

    Of the 3 main Ball Clays available in Australia (Ball Clay FX, Ball Clay R and Clay Ceram) Ball Clay FX has a very similar Chemical analysis. The TiO2 content is fractionally more whilst the Fe2O3 is slightly less. I have successfully substituted Ball Clay FX for OM#4 in glazes tests. However which ever you choose should be tested first as analysis change depending on what part of the pit is being mined. I have found the Glaze Program Matrix by New Zealand ceramist Lawrence Ewing to be spot on. This program has analysis of all the main materials used in Australia. It's database of materials used world wide is extensive. It is really easy to substitute Australian materials for materials used elsewhere and make the necessary adjustments. It is the best money I have spent on glaze calculation programs for my needs in Australia. Johanna
  16. China Decal

    Hi John I didn't see that these decals were any cheaper in price when I purchased them from Chinese Clayart but I guess they are made with "cheaper" materials. It is painful to have to throw them away as I pay at 50% on top of the value of my decal order in postage to get them to Australia and I have to buy in larger quantities to make it worthwhile. However I do go with the old addage "once bitten, twice shy" Regarding the "look" of these decals on purchasing, they look like and feel like clingwrap (term used in Oz for light plastic used in kitchens and very much like drycleaners plastic). The covercoat is also clear thus making it more stressful for failing eyesight. Working with it is a bit like working with spiders' silk. Regards Johanna
  17. China Decal

    In my experience there seem to be some really big issues with these decals. The first issue is that they are extremely fragile in attaching to the surface following the instructions given in Chinese Clayart, California.. They do not want to stick very well to the glaze surface once floated on. They are at risk of adhering to your fingers, squeegees or sponges once on. They will adhere to themselves very quickly if creased and are impossible then to smooth out. The second big issue is that they burn out very readily. Do NOT assume that you can fire them at the temperature you normally use for the conventional decals. The ceramic colour used fluxes at a much lower temperature and runs. I fire all my work to 810.C including decals as I work wirth porcelain and the glazes I use need that temperature to accept the overglaze at its optimum. In my opinion (I do have a lot of experience with decals), this type of decal is not worth buying as the failure rate is high . You would be better served finding ones that have the conventional cartridge paper backing as well as the heavier covercoat which gives greater rigidity yet flexibility and a much wider and reliable firing range. Regards Johanna
  18. is gilding / gold leafing food safe ?

    name='dontstareatthesun' date='17 January 2013 - 09:53 AM' timestamp='1358380420' post='27980'] The Japanese frequently use this technique. and that would be food/drink safe ? Hello Kennedy Gold for use in ceramics comes in the following forms: 1. Powder 2. Leaf 3. Liquid as Liquid Bright Gold (different concentrations) and Burnishing Gold. I have attached a PDF of the relevant section of Kenneth Shaw's "Ceramic Colors and Pottery Decoration" This will explain to you all that is known about gold and ceramics. And yes, fired gold leaf is food safe. I beg to differ with your initial statement that "but after some googling I found out that gold luster is not food safe" I would be interested in viewing your links on this. The other attached PDFs should settle your mind about the food safety of gold as well. Below is an edited copy of an email reply that I sent to Dinah Snipes Steveni in July 2012 after she contacted me regarding gold and food safety. "My first thoughts when I read this are: Rosenthal uses Liquid Bright Gold and Burnishing gold lavishly on rims of domestic glass and pots and the EEC has the most stringent guidelines for ceramics production in the world. For those of us who can afford it, dentist still use gold for fillings Gold powder/flakes are sprinkled on the food and eaten. Gold is a pure base metal and it is used in overglaze by extracting the salt of the metal through the use of aqueous regis. For LB (Liquid Bright) and burnishing gold it is then modified by adding mediums and solvents to facilitate its application. These burn off during the firing leaving the pure gold attached to the surface of the pot around 800.C depending on the glaze type being used. Gold itself melts at approx. 1060.C and starts to vapourize. Gold is also used as a powder and paste. I have attached 4 PDFs showing the use of gold, the MSDS and CAS# readings to interpret the MSDS. I get my gold from Fay Good (http://interdec-australia.com.au) and I am pretty sure they source their gold from Heraeus in Germany. You will see from the Fay Good MSDS that all components bar the gold resinate are either mediums or solvents. You can check their MSDS through CAS#. They all burn out, though I must say it is pretty toxic to breathe in the fumes during the firing. After 450.C all seems to burn out and you can breathe the air again around the kiln. The hysteria that surrounds the leaching with potters is that they don't do the research to fully understand what is going on. The main culprit with leaching is that lead is used as a flux for lower temperatures. If a glaze is properly constituted and fired to its optimum temperature it will not leach but there are too many variables with individuals and companies taking short cuts so that the use of lead frits has been regulated and lead oxide has been banned in the EEC ceramics industry. However many potters don't realize that once the kiln is contaminated with lead fumes it will be contaminated for a long time. I must point out here that neither gold nor lustres have any lead in their formulation. With the perceived leaching problems with Overglaze colours potters don't take the trouble to find out all the facts. Overglaze colours(commonly known as China Paints) are in fact just a very low firing glaze. In the past these have been based on lead as the main flux. Because people (both potters and decorators) are notorious for picking their own firing temperature instead of the maximum recommended, the lead is not always locked in. Now regulations have been brought in by the EEC that ware cannot have more than the allowable level of lead in the decoration from where it touches food or liquid so a whole lot of research has been done to find alternatives for lead as a low firing flux. They are now using a boron based flux. I don't know whether that has happened yet in the US. However in China they are still using lead so be careful when buying any overglaze colour that you can't verify its source. If it is not in contact with food then there is no problem in the fired state. The problem lies in its powdered state. Don't smoke and take care with the dust and also food in the studio. Don't lick or chew the brush which surprisingly a good few people do. Another thought that passes through my mind is that gold is really expensive and the price of the work should reflect this. Why would a potter then expect that a piece with a gold interior should be used? It is easily abraded. For me gold is used to make a statement. It is like the icing on a cake. However if you cut the cake you destroy the icing. Reading back through this I sense that this sounds very much like a lecture. I can assure you that it isn't. I just get very passionate about all the misinformation that floats around today. I see this as a result of everybody wanting to be seen as an artist without having any basic training or taking the trouble to acquaint themselves with the knowledge about what they are using. Everybody is trying to reinvent the wheel for their own ends but sadly without knowledge the wheels are turning out square." As I seem to have run out of upload space here is the link for the Heraeus PDF on the use of gold on dinnerware. http://heraeus-preci...china_home.aspx Regards Johanna Gold.pdf CAS 7440-57-5%20%20 GOLD.html MSDS Liquid Bright Gold.pdf Gold.pdf CAS 7440-57-5%20%20 GOLD.html MSDS Liquid Bright Gold.pdf
  19. is gilding / gold leafing food safe ?

    Hello Neil Genuine gold leaf can be fired onto the surface of the fired glaze. Imitation gold leaf can't. Some research will corroborate this. Johanna
  20. Lusters article in CM by Johanna DeMaine

    Hello Mark As Marcia mentioned I live in Australia. However I find the that I can get any lustre colour that I want. It is true that only a few basic colours are kept by ceramic suppliers but this is a demand issue and not availability of colours. Lustres and overglazes have never been seriously stocked by ceramic suppliers. If there is no demand then the stock get diminished and then not restocked. Added to this is the fact that lustre needs to be kept refrigerated especially the gold based lustres which include reds, pinks and some blues. I came to the conclusion long ago that I would be better off getting my supplies from china painting/porcelain painting suppliers or more to the point their suppliers. Lustres go in and out of fashion even in the porcelain painting world and there are lots of little suppliers who just augment their arts practice and do not carry a great range. Changing the mindset about shopping habits is the first hurdle to overcome. Australia like USA is a vast country and we are seriously underpopulated. I now source all my overglaze supplies globally online. We are fortunate that we live in an era that online shopping is so easy now. I get all my lustres from Fay Good, Australia http://interdec-australia.com.au/ They have a full range of colours and they supply many people in USA. In the UK there is http://www.held.co.uk/. I can recommend both these suppliers and have never had to wait more than 7 days to receive an order. I am led to believe that they both stock Heraeus products. This company is one of the main manufacturers of overglaze and precious metal products in the world. The ceramics world is only a small part of their target audience. I believe there is Sara lusters in the States but I have had no dealings with these people so I cannot comment on the quality and availability of their product. By the way the ingredient causing "the luster headaches of the 70s" would be turpentine. Many oil painters also have a problem with this. Regards Johanna
  21. I would like to add to this discussion by adding the following for consideration. Firing to a higher bisque(looking at the vitrification temperature of the clay body) than glaze temperature, came about with the onset of the manufactories that produced ceramics in bulk and were interested in a high success rate. By bisquing to vitrification the warpage factor was dealt with before any time or effort was invested in glazing and decorating the ware which could be lost through warpage. It must be remembered that profit was the motivating factor for this. However this comes at a price as ware fired at a lower glaze temperature does not fully develop the glaze interaction layer (that is the zone where the glaze and the body interact). This is the zone where glaze fit comes into play as well the the development of certain glaze attributes. This can be seen by comparing the quality of glazes fired on high bisque at a lower temperature to glazes fired at a higher temperature at a lower bisque. These glazes do not have the depth or "soul" for want of a better word. They are more akin to a coat of paint than a full integration with the clay body. Another downside is that the glazing process becomes more problematic. The glaze has to be "doped" to be able to adhere to the non porous bisque. Industry has the technology to deal with this whereas for the studio potter it creates more difficulty in getting enough glaze on the ware to get a good depth of coverage. I work extensively with multiple firings at 800.C (cone016-015 depending on firing speed). However I still glaze at vitrification point (Cone 10) after a Cone 04 bisque. This allows me to add extra colour and effects to the surface with overglaze (otherwise known as onglaze or china paints). However these colours just sit on the surface and don't integrate with the glaze. However if I were to fire this higher say at Cone 04 upwards these colours (though NOT lustres) would begin to sink into the glaze and become not so intense. This then then becomes known as Inglaze colours. Overglaze work can be done at any temperature. Cone 6 glazes can be fired over a Cone 10 glaze as can any of the low fired glazes. The problem then is the same as for any overglaze work: getting it to adhere to a higher fired surface. Johanna
  22. I have just spent some time throwing and sandblasting some Southern Ice porcelain for new celadon work with overglaze for a solo show opening 22 September. Because of our geographical location there is a distinct shortage of competent photographers in our neighbourhood. Through necessity I have learnt over the years to photograph my own work. I feel that I have succeeded to some degree with my lustre work using a light tent. However I am now trying to photograph the celadon work to show the translucency and this is a whole new kettle of fish. I am aware that light placement and background colour is very important Can anybody give me some advice on how to tackle this problem. I would be very grateful for any help offered. With thanks Johanna
  23. Thanks for that. I will have to purchase the book for future reference. Will try to nut this out from Antoinette's advice. I will post my results. Regards Johanna
  24. Thanks John. I have a received a reply from Antoinette and am investigating the settings. Will put up a report of my outcome/results in the next week or so. Regards Johanna
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