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SweetheartSister

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  1. Oh, that makes sense! So put in the freezer for a day, take out and straight away pour over boiling water in the sink? Do you carry out this test with every single batch of mugs you fire, or just the once if you're duplicating the variables such as firing time/temp, layers of glaze used, same glaze and same clay etc?
  2. Oooh okay, that sound straight-forward enough to do. Is it important to make sure that you're testing with the exact item, e.g. using a cast out pendant to test rather than a different casting/piece of clay which is a different size? Like if I were to glaze a mug and a pendant in exactly the same way and fire them for the exact same schedule, would the results be different due to scale of the items? It makes the most sense for me to cast out some pendants as tests, but I'm just really curious as to what the variables are here
  3. Thank you Roberta12, Min and Neilestrick; it seems that the verdict is to try the overglaze on top of dry underglaze so that I don't have to fire 3 times. I'm going to do some test pieces and see how that goes. In the future I would definitely like to put a clear overglaze on some of these designs, but I am still fearful of crazing happening even a year down the line, which is what has happened on some of my earthenware pieces. Is there a fool-proof way to be sure that the glaze fit is definitely okay? I actually contacted a factory recently about batch producing some of these pendant designs in earthenware, but when I asked if they would eventually craze, they said definitely. I also spoke to my kiln supplier on the phone and he said that porcelain is a much safer option regarding crazing because it is a much less porous clay than earthenware. As I'm selling these, I just want to be sure that they will last a long time so that my customers are happy
  4. Thank you for this very detailed explanation, Min. I honestly appreciate it so much. I feel a bit stupid, firing the underglaze to vitrification temperature - I know that glazes don't take well on vitrified clay so I'm not sure why that completely went over my head. With regards to these pendants, they actually look really nice as they are without an overglaze, so for this batch I will leave them as is: 20190923_074045 by Rachel Brown, on Flickr If I wanted to repeat this process to accomodate a transparent overglaze in the future, do you think the following would work: 1. Bisque fire casts to Cone 05 2. Paint on underglaze and fire to cone 015 to burn off impurities 3. Paint on overglaze and fire to cone 7 (will mature at 6) to create final, vitrified piece. I don't think I could do liambesaw's suggestion of painting onto greenware, as the pieces are so fragile before bisque firing - it is very easy for example to chip off an ear on a pendant once dried. With regards to crazing, the supplier has recommended this exact overglaze to pair with the slip I am using from the same supplier. It is designed specifically for porcelain. So hopefully it will be okay, so long as I fire to the correct temperatures.
  5. I have a few dozen porcelain pendants in the kiln right now. This is my first time using porcelain and since having a bad experience with crazing on my last pendants (in earthenware) I really don't want to mess it up. This is what I've done so far - 1. Bisque fire to Cone 05 at medium speed. Although I have now discovered that if you don't put a hold on my electric kiln, it will shut off when it reaches each temperature and will not soak the ware at that temperature. So going by my pyrometric cones, they reached cone 06 (orton cone puddled) but did not quite bend my 05 cone. 2. Then I hand painted my pieces with Amaco Velvet underglazes and set the electric kiln to cone 7, firing at medium speed once again. This means it will definitely mature at cone 6. Firing range of the slip I'm using is 1220 - 1300 celcius. Cone 6 is 1220. I've put orton cones in again to be sure that the ware reaches cone 6 and therefore vitrifies. 3. The final stage will be to apply the transparent overglaze. This also has a firing range of 1220 - 1300. Should I fire at Cone 7 again? Should I fire on the fast setting or on the medium again? I have a Paragon Firefly kiln and according to the manual the medium speed is 'standard', the fast speed is 20% faster and the slow is 20% slower. I want to make sure I get these right this time, but feel quite nervous. These porcelain pendants will be used as part of fine jewellery pieces and I want them to last many many years and not craze on the surface. Thanks so much everyone.
  6. Thanks Bill and Liam for the advice. I'm going to experiment with it and will let you know if it is successful
  7. Just a little thought I had today...if I wanted Cone 6 fired porcelain to have a satin/low gloss finish without the use of an overglaze, do you think that I could achieve this using a rock polisher? I'm talking about very small items - pendants and beads. I would be interested to know if anyone on here has ever tried putting porcelain in a rock tumbler machine before?
  8. Hi Min, thank you for that suggestion because I would have never thought of that. If the method I'm trying today doesn't work out then I will certainly give that a go!
  9. The problem is that I can't really dry foot them. They need to be glazed all over. They are very small, 1cm -2.5cm each. Surely there must be ways to stilt or suspend porcelain that needs to be glazed all over, such as dolls? These are the pendants (pre-bisque fire) They have holes in the heads where the pendant bails will go - they could slot onto wire uprights on these. 2019-09-14_12-59-59 by Rachel Brown, on Flickr
  10. That is good to know Bill, thank you! I'll give the alumina and wax a try
  11. Thank you for your helpful response. I do have a homemade bead rack which I've used with success in the past, but with the case of these pendants, the holes do not go the whole way through the sculpture, meaning that they can't be threaded onto a bar. So the only way to suspend them is by slotting them onto an upright piece of wire stuck into a clay slab. It has worked for me many times with earthenware, but this is my first time using porcelain. I'm hoping that as the pendants are so very tiny, they won't slip down onto the sticks and get stuck. They are very light weight. I guess I won't know until I try.
  12. This might be a silly question, but I remember reading somewhere that porcelain cannot be stilted because it becomes very soft during firing and will slip onto the metal wires. Is this true? I have a collection of small porcelain pendants to fire, ranging from 1cm - 2.5cm. I was planning on bisque firing them on a shelf with kiln wash to 1000 celcius. After underglazing, I was going to suspend them on a homemade stand which is basically a slab of clay with nichrome wire sticking out of it. Each pendant has a hole in it so it can be suspended without the underglaze/overglaze touching anything. This is what I have done successfully in the past with earthenware, but will it work with porcelain? I'm aware that I will need to make a new stand in porcelain which will be okay during high fire. Many thanks in advance for your advice
  13. Does anyone know of any companies, preferably in the UK or Europe, who will batch manufacture porcelain for designers? I've found a few places in the UK who will do so in earthenware, but not porcelain. Any leads would be super appreciated! Looking to just get pieces cast/bisqued ready for hand painting.
  14. I've been advised that earthenware will always craze eventually, because it always remains slightly porous. Is this true? I've been advised that porcelain is a better bet for product longevity. I make and sell ceramic jewellery. Have been using earthenware up until now but am considering porcelain. The only thing is I've heard it takes a lot longer to slip cast. Would love some opinions on this from the experts on this forum
  15. Both I guess - I want to know if they are particularly dangerous for me to use, and also if they would be any danger to the wearer of say a pendant decorated in china paints. I have used Amaco underglazes on my earthenware jewellery in the the past, so maybe I could try these again on porcelain, although I'm away that the colours would change at high firing temperatures.
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