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Ceramics and Toughness

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  • Ceramics and Toughness

    I've begun experimenting with new product design crafted in ceramic, specifically biscuit/bisque-fired earthenware, and quite like it's textural properties in the unglazed state. The product roughly resembles a deep soup bowl no larger than 12cm in diameter with a wall thickness of about 3mm.

    My question would be, how does biscuit earthenware compare with other ceramics in terms of toughness when dropped? Would a similar piece in stoneware, porcelain or another ceramic better withstand impact? Please describe their strength. Is their an additive used to produce a more resilient ceramic?

    Thank you!
    Silas

  • #2
    Hi Silas,
    suggesst you contact CERAM Research http://www.ceram.com/
    www.toppotsupplies.co.uk

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    • #3
      Ceramics and toughness

      Thanks for the suggestion. CERAM would no doubt be able to supply an authoritative answer, but before it becomes necessary to go down the route, any general experience among members here on the strength and ease with which earthenware, stoneware, and porecelain break would be of interest. Let's assume all of these have been fired to maturity (not simply bisque as previously mentioned).

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      • #4
        As the hardness increases I'm wondering if the brittleness increases? If you look at hotel ware however they always use a vitrified body. Of course the hotel ware market is very anti chip resistant which is the major failing of earthenware domestic ware.
        www.toppotsupplies.co.uk

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        • #5
          This is a difficult question really. I think it goes without saying that the higher the firing temperature the more resilient the ware will be (stoneware is vitreous and will withstand frost and it doesn't chip easily, earthenware is much less resilient, and biscuit fired ware is very fragile)

          All pottery / stoneware is likely to break if dropped, whatever it's been fired to (as I've found out to my cost on more than one occasion) Your question as to what breaks most easily depends on so many factors that it's almost unanswerable. What is it dropped onto? From what height? How thick is the piece?

          I totally understand your reasoning about liking the texture in an unglazed finish. A glaze obliterates much of the fine detail in sculptural work. For the same reason, we use iron oxide mixed with water, dip the piece and then wipe off with a sponge. Much of it will stay in the nooks and crannies and gives highlights and depth of colour without obscuring the detail. Fired to stoneware temp you can get lovely gradations of colour from beige through deep red right down to blue black.

          Re your original question I think one of the reasons you haven't had loads of replies is that none of us really know the answer and may not really understand the reasoning behind the question (at least I don't - I shouldn't speak for others I suppose :-)

          (Welcome to Leicester by the way. Where abouts are you? We're in Syston, near Melton Mowbray)
          Kate
          www.cuckoos-nest-fairs.co.uk

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          • #6
            Thanks very much Kate. I'm living near De Montfort University where I'm currently attending an MA course. Allow me to supply more details now on the nature of what I'm attempting to do. The product/piece would typically be placed in living rooms, mounted on a stand 1m high. It's in the shape of a half sphere with a wall thickness of 3mm. Any surface that it may fall onto is as varied as living room floors can be, but regardless whether it's stoneware, earthen, or porcelain, I assume that a fall from 1m would inevitably be destructive.

            I gather the higher the temperature firing clays are generally stronger. Hardness doesn't always equate with toughness (A very hard substance can in fact be more brittle) and it's toughness that's of interest in this application.

            The unglazed earthenware I've been using has had stains mixed into the body to achieve a few separate colours to offer the product in: a sandstone, a gray, and a plain off-white. The fact that the colour is through and through the body is of value in that the colours are not finishes but rather honest evidence of the material.

            A study of texture is also the focus now. The ceramacist I've been working with throws the pieces on a wheel leaving fine textures in the clay from her fingertips. We've experimented in both earthenware and stoneware. The earthenware has certain benefits in terms of shaping or manipulating the piece after firing, as three holes are to be made at the bottom of a very precise diameter, as well as the open face of the piece which also has to be expanded to a size with mm precise tolerances. The vast majority of the surface, however, remains untouched and the fine texture from here fingers is clearly visible and a pleasure to handle.

            As eathernware is relatively porous, oils from the hands in handling the piece will show up on the surface, particularly in the white version. To add a glaze utterly destroys the fine tactile pleasure and the visual sense of it. In practice , the pieces will not be handled much once installed in a room, but the question of how much an issue this porosity will be remains.

            I've found similar unglazed products, a water pitcher from Sweden for example, where the material was of a bone china with a wax applied in lieu of a glaze allowing the pitcher to be handled. It's effective, but the material, it's look and feel, is not as appealing as the unglazed earthenware.

            Ultimately, the piece will need to be precisely reproducible in batches (between dozens and hundreds) using a mother cast from the ceramacist's original. What is sought is a way to maintain the pleasing tactile and finish aspects of the earthenware currently used, yet hopefully increase its handleability and resistance to marks and oils from the hands, and its toughness in the event of a fall. I suppose that I'm attempting to provide a product which has traits and qualities of a crafts piece, but is at the same time, doing so with an industrial kind of discipline. I seek to retain the warmth and pleasing tactile experience that the human touch leaves mapped onto the surface, but at the same time it must be precise in form and entirely reproducible, accurately.

            In terms of strength, I'm certain the piece will remain abuse-intolerant, but whatever can be done to improve this aspace needs to be fully explored. Reproducing it on some scale is then the next concern. I understand Stoke-on-Trent is the centre of the industry here but facilities in Asia may also be worth considering. After some further research on methods of reproducing the piece, a visit to a UK studio of facility capable of reproducing the piece perhaps in Stoke or elsewhere will be in order. Any recommendations and advice would be most welcome.

            This is the piece, before modification. The texture on the interior fascinates me and should be brought to the exterior as well.

            texture.jpg

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            • #7
              Yes I wondered why you were asking this too...why would you want to make anything out of ceramic and then drop it ? Better use wood or metal if that was what you were planning to do with it

              Firing any clay to it's optimum maturing point is the way to get the most strength from it. Biscuit ware is not fully fired and therefore the pottery will not be at full/optimum strength....

              it depends also on what sort of clay is used. Like the others have said stoneware is tougher than earthenware. but stoneware themselves clays vary in their constituents and this affects their fired strength.

              My guess is that when bisque ware is dropped it will shatter into many peices whereas when fired stoneware is dropped it may break maybee in half or into larger and fewer pieces.
              http://www.dosrodgerspottery.co.uk/

              Comment


              • #8
                Originally posted by Silas View Post


                Ultimately, the piece will need to be precisely reproducible in batches (between dozens and hundreds) using a mother cast from the ceramacist's original. What is sought is a way to maintain the pleasing tactile and finish aspects of the earthenware currently used, yet hopefully increase its handleability and resistance to marks and oils from the hands, and its toughness in the event of a fall. I suppose that I'm attempting to provide a product which has traits and qualities of a crafts piece, but is at the same time, doing so with an industrial kind of discipline. I seek to retain the warmth and pleasing tactile experience that the human touch leaves mapped onto the surface, but at the same time it must be precise in form and entirely reproducible, accurately.

                I understand Stoke-on-Trent is the centre of the industry here but facilities in Asia may also be worth considering.
                Thanks for the further information. But now I'm even more intrigued to know what exactly the piece is. The picture showing only a part of it is like a little 'teaser'. Is it functional ware, or is it a piece of art? If the latter, why do you want to reproduce it in hundreds? What is the purpose of the three holes? And why are you so preoccupied with it falling? All ceramic ware is breakable if not treated with care - is there some intrinsic feature of this particular piece that makes it more vulnerable to falling or being dropped? Or even (the imagination is really running riot now!) is it to be thrown on the floor at a Greek wedding??

                Please enlighten us before I start losing sleep trying to work it out (I love a good puzzle anyway!)
                Kate
                www.cuckoos-nest-fairs.co.uk

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                • #9
                  It's an enclosure for an audio-visual product such as a television or a stereo (although neither of those is exactly what it is, sorry!) where both its functionality as well as design aesthetics play vital roles...in short, it's all about product design. The use of ceramics would not normally be the first choice in terms of the function the material needs to fulfill, but it contributes heavily to the product's uniqueness in its market niche. The intent is for potential buyers to have the same level of regard for the item as they might have for any ceramic artist's work. The item is perfectly spherical (which would make it more vulnerable to falling) and sits in rubber ring base or is affixed atop narrow stands.

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