Jump to content

PeterH

Members
  • Posts

    1,413
  • Joined

  • Last visited

Everything posted by PeterH

  1. It looks like this URL may show both sides of one of the 3 parts of 183F https://www.ebay.co.uk/itm/134337508508
  2. https://digitalfire.com/material/petalite Petalite is a lithium aluminum silicate mineral (more simply a lithium feldspar) that is commonly used in clay bodies. It is valuable because it provides an insoluble source of lithium and has the highest Li2O:Al2O3 ratio of any natural mineral. Lithium is a strong alkaline flux and is effective over all temperature ranges. It imparts lower expansion and gives a unique color response to copper and cobalt in glazes. Some commercial versions have a chemistry that fairly closely matches the theoretical chemistry given here. Petalite is most prized for its mineralogical properties. It is especially valuable in imparting thermal shock resistance to clay bodies because it has almost zero expansion when heated above 700C. Bodies with 60%+ petalite can take a direct flame and rapid water cooling without failure. To make a plastic clay body mix petalite with as much ball clay as needed. For a casting body, use as much kaolin as needed to achieve the desired casting properties. Bentonite can be added to either type of body to increase the petalite proportion. One serious problem with low expansion petalite bodies is that it is very difficult to achieve glaze fit. All common glazes will craze. This is compounded at lower temperatures where the limited low-expansion silica and alumina necessary for melting raises glaze expansion. For some low-expansion bodies, it is almost impossible to match a glaze
  3. Yes -- and it will probably be impossible to de-mould. ... although I have a very vague memory that I seen mention of a sacrificial "core" -- which burns-out/crumbles during the firing -- being used in some circumstances. Somewhat tongue in cheek, a picture of ancient Peruvian pan-pipes from https://digitalassets.lib.berkeley.edu/anthpubs/ucb/text/nap002-003.pdf My understanding of the paper is that the pipes were cast individually and then joined by adding additional clay by hand (although the set of individual pipe moulds for a complete panpipe were held in a common mould structure). Seriously, what is the intended usage of your end-product. It will enable us to understand the importance of the precision you seem to be demanding. It might also mean that the inevitable shrinkage & warpage of clay products during both casting and firing may render your product unusable for your intended purpose (a point already raised by Mark).
  4. Any idea of the manufacturers code for this item? For example looking through https://img1.wsimg.com/blobby/go/a473195b-32be-4831-aad8-e122a50bcf46/IN THE KILN CERAMIC GREENWARE-BISQUE LIST.pdf gives ... but I failed to find more details on the site. Searching for 183F elsewhere give: https://bisquebusters.com/products/scenery-mountain-train-3pc A more general search found this, but without a manufacturers code https://www.ebay.co.uk/itm/134018515130
  5. There are also a couple of Nigrosh's Egyptian Paste recipes under glazes. PS Googled site:glazy.org Nigrosh
  6. Low Fire : OTHER Ways to Work in Clay Leon I. Nigrosh? If this is the right book 2nd hand copies seem quite cheap (<$5). https://www.bookfinder.com/search/?full=on&ac=sl&st=sl&ref=bf_s2_a1_t1_1&qi=jZ9txr1bouNCtZ9PoXMfx.wd7CM_1704364091_1:11533:21043
  7. Are you trying to make a set of panpipes or a high-tech industrial component? It would help if you gave us an idea what you are trying to make, and the use to which it will be put. This gives the experts some criteria to judge the merits of alternatives production techniques. Two minor points. - If you use multi-part moulds don't draft-angles become irrelevant, although parting lines may require tidying. - Is extrusion an option?
  8. I was fascinated by mainstream and "alternative" photographic techniques as a child. So some book knowledge and no practical experience with images on clay. What is the name of the process you are using? @blackthorn has been a/the major contributor to several threads on photo-lithography and other image transfer techniques. He seems to have tried many processes, often with mixed success, and the best results I remember are from a ink-jet printer based idea, mentioned in a weakly-related thread. In reply to your specific questions: There are several types of linseed oil (raw, refined, stand, etc.) and it seems like they have either recommended a particular type (all different) or just said "linseed oil". Some say to use gum arabic and others don't mention it. There are lots of process and gum arabic is used in at least two different ways. 1) Relying on the fact that oil and water don't mix. For example a very simple process of taking an image from a photo-copy. Photolithography on Clay https://pistrucciartworks.wordpress.com/2011/03/20/photolithography-on-clay/ 2) Using gum as the basis of a photo-emulsion, where the gum hardens when exposed and the unexposed gum can be washed away. [Having the same problems as newsprint -- limited tonal range and sometimes needing the use of half-toning.] Some process issues Trouble w/ Cyanotype on Bisqueware Discussion of three variations on the theme: classical cyanotype, gum bichromate and gum with masion stains. PS There are H&S issues with gum bichromate
  9. Just my take on this. Certainly as a term "memory" has its problems, not least the implication of some sort of consciousness. However "local platelet alignment" is a real property, that can cause the previous history of the clay to influence its future behaviour. An effect that sometimes has practical significance. Techno File: Clay Memory https://ceramicartsnetwork.org/ceramics-monthly/ceramics-monthly-article/Techno-File-Clay-Memory# Crack H in Hamer & Hamer http://ceramicsfieldguide.org/pdf/materials-handouts/ClayCracks.pdf PS "Squeezing out water" may sometimes relate to changing platelet alignment so there is less inter-platelet space to hold residual water. A similar effect occurs during hard-panning, but in this case caused by excessive deflocculation rather than physical manipulation.
  10. I've no practical knowledge, so treat this all a here-say I'm interested in how you get on, but ... - I don't think either bones -- or seashells -- will survive high firing sufficiently intact to act as a stilt. - I doubt that bones will help form a "glaze" in the same way that seashells do. Firstly I think shells are used as a separator between the pot and clay wadding placed inside the shell. Shells seem a much better shape for this than most bones. Effective Side Firing https://ceramicartsnetwork.org/pottery-making-illustrated/pottery-making-illustrated-article/Effective-Side-Firing# While wadding is traditionally only used in atmospheric kilns to prevent pots from sticking to the shelves, it is necessary for side firing in electric kilns. Sea shells turn to powder (calcium oxide) during the firing, and will not support the weight of a pot. Using wads under the shells prevents the pot from falling onto the drip tray and sticking to it. Secondly the chemistry is different, perhaps critically so. Shells in Ceramics https://www.weloveclay.com/read/53007/53007/ Why then were shells not adopted more widely? Australian wood fire potter Owen Rye has pointed out that though ancient potters were keen observers of their craft, none could have understood or intuited the science of shell use. The shells themselves are formed from calcium carbonate which, when heated, converts to calcium oxide or ‘quick lime’, a powerful flux. In isolation, calcium is one of the most refractory oxides, only melting at 2572˚C+. But combine that calcium with alumina and silica and you have what is known as a ‘eutectic’ – a combination of oxides that melt at a lower temperature than they would on their own (in this case, a much more manageable 1170˚C). Why then were shells not adopted more widely? Australian wood fire potter Owen Rye has pointed out that though ancient potters were keen observers of their craft, none could have understood or intuited the science of shell use. The shells themselves are formed from calcium carbonate which, when heated, converts to calcium oxide or ‘quick lime’, a powerful flux. In isolation, calcium is one of the most refractory oxides, only melting at 2572˚C+. But combine that calcium with alumina and silica and you have what is known as a ‘eutectic’ – a combination of oxides that melt at a lower temperature than they would on their own (in this case, a much more manageable 1170˚C). All this means that on the interface between shell and pot there is a melt that leaves a shell-like scar on the surface of the clay. As the shells are stuffed with clay to prevent them from collapsing, the same happens on the inside. The core of the shell remains pure calcium, which is dry, friable, expands when wet and can be easily removed after the firing. An aesthetic bonus of using seashells is that they contain small quantities of salt. During the firing, this salt can volatilise, leaving a subtle halo of salmon pink or orange on lighter coloured clay bodies. Shells decompose into calcium oxide, bone eventually decomposes to a mixture of calcium oxide and phosphorous pentoxide, which may well prevent a suitable eutectic forming. Also bone ash tends to retain some of its structure, probably making both oxides less available for forming a "glaze". https://en.wikipedia.org/wiki/Bone_ash Bone ash is a white material produced by the calcination of bones. Typical bone ash consists of about 55.82% calcium oxide, 42.39% phosphorus pentoxide, and 1.79% water.[clarification needed] The exact composition of these compounds varies depending upon the type of bones being used, but generally the formula for bone ash is Ca5(OH)(PO4)3. Bone ash usually has a density around 3.10 g/mL and a melting point of 1670 °C (3038 °F). Most bones retain their cellular structure through calcination.
  11. +1 for starting another thread. I'm used to seing rather chunky rubber block moulds on the net. As from 6:53 in this video. How thick are you printing the walls? Would these rubber moulds be self-supporting when casting into them, or would they need a "backup" mould to prevent distortion? ... which I believe is common practice in some areas. How to Make Backup Mother Moulds https://www.aldax.com.au/backupmould.htm
  12. I had a vague memory of possibly related postings using IR thermometers and/or IR cameras. Having been impressed by images such as this one showing an overheated relay lead. Turns out it was from one of your postings, What's your current position on these techniques? PS I also have a vague feeling that some mobiles were sufficiently sensitive to IR to give useful images.
  13. Help, I'm having trouble understanding these figures. Problem 1. 28+23+28=79Aamps, but the 240V kiln seems to be rated at 60amps. https://www.sheffield-pottery.com/SKUTT-KM1231-3PK-240V-1PH-p/skkm12313pk.htm ... note that 79/sqrt(2)=55.9, so it might be interesting to know if the current sensor is reading RMS or not. Problem 2 Currents of 28+23+28 indicate that the centre section has a higher resistance than the end sections. But the ends seem to have 2x 8.9ohm elements in parallel, and the centre 3x 11.3 ohm elements in parallel. https://skutt.com/images/KM1231PK-1PH-and-3PH.pdf https://www.armadilloclay.com/uploads/5/1/2/8/51288343/element_resistence.pdf So, ends should be 8.9/2=4.45ohms & the centre=11.3/3=3.76...ohms. ... where the centre has a lower resistance than the ends ... and the currents are very high at 240*2/8.9=53.9amps, 240*3/11.3=63.7amps and 240*2/8.9=53.9amps compared to 28-23-28.
  14. You may find these of interest if you are going to make your own paperclay. HOW TO MAKE PAPERCLAY | Chris Campbell http://www.ccpottery.com/colored-clay-lessons--chris/how-to-make-paperclay-.html Great if you have a heavy-duty mixed. If you don't you may have to resort to adding the damp paper-pulp to a pre-made thick clay slip, or adding dry clay powder to a wetter paper-pulp mix. In either case it will take longer to dry on a plaster slab due the the greater water content. Making Paper Clay Storage Easier and Less Stinky https://ceramicartsnetwork.org/daily/article/Making-Paper-Clay-Storage-Easier-and-Less-Stinky
  15. Interesting to be reminded of prior work, but from pp74-75 of the 2nd edition of Contemporary Studio Porcelain by Peter Lane (2003). The methods used to make the components for constructing his sculptural installations were developed during a ten-year period of intensive experimentation and intensive research. ... The procedure of actually casting thin slabs of porcelain is the the most difficult part of the whole process of manufacture because small mistakes can create big problems. The most common faults resulting from incorrect casting are: cracking, warping, and distortion with corners curling to destroy the flatness. The details of the process cover about a page of A4. Rolling paperclay seems likely to be a lot easier and more fault-tolerant. PS If you are interested in the book, it's available from A$40 via https://www.bookfinder.com/search/?full=on&ac=sl&st=sl&ref=bf_s2_a1_t1_1&qi=iA,O6ra27IBsie2OptRYjTAhne4_1702997710_1:9810:16802 ... check against other sources such as Amazon
  16. I would take a very careful look at Neil's suggestion. A very plausible cause of baffling problems, and you can check if it's causing your problems with a very simple wiring change. As Neil says it's a long shot, but if electrical interference is the cause it's going to be practically impossible to identify by normal diagnostic procedures. To me trying his suggested fix is a no-brainer, the cost/potential-benefit is so one-sided. ... but I'd continue exploring other options in case it doesn't work out.
  17. I'm certain you will enjoy experimenting with paperclay. Just measured my printer paper, it's 0.06mm thick (a stack of 500 sheets measures 3cm). I cannot see you getting anywhere near that. OTOH playing with home-made paperclay years ago I achieved 2-3m very easily with a rolling pin. I just rolled it out on under a cloth on a slightly porous surface and draped it onto a balloon. Handling thin sheets, especially when drying, may be an issue. Pouring slip seems to be trying to cast it. I cannot see you getting thin sheets this way -- or getting them off the casting surface either. Weakly related article. THE MAKING OF PAPERCLAY PORCELAIN BANNERS https://www.grahamhay.com.au/harrison1998.html I mention it because he achieves 1.0-1.5mm with rolling. Which I suspect you could do with most paperclays. Using a light weight cellulose/cement batt as a backing, spread a jumbo garbage bag over the batt, held in place with paper clips. Spead a layer of paper clay mix fairly evenly over the plastic sheet with a spatula. Place another sheet of plastic garbage bag over the top and roll out the clay in all directions with as much pressure as you can muster until it oozes out off the batt on all sides. Alternatively, the batt can be placed on the slab roller and reduced in that way. Keep rolling until it is as thin as you can get it. PS Not relevant to you, but an interesting idea I haven't seen before, using ceramic fibre to strengthen the clay during firing (after the paper has burnt out). He apparently needed to do this because he was using very highly/deeply textured sheets. Firing is to Orton Cone 8 in 4 to 8 hours, depending on the decoration. If the marks are many and vigorous, a longer firing is required to stop the tile splitting up along the incisions. This is why the ceramic fibre is added, as it doesn't bum out like the paper but persists. The paper does a sterling job at room temperature of binding the surface together but the tell tale waft of smoke at 250,C spells its end, and that is when the normal paperclay tile will crack if the fibre isn't added, as the fibre remains intact until elevated temperatures resisting any tendency in the tile to crack apart along the stress lines created in the decoration. Eventually the ceramic fibres dissolve into the ceramic body glass, which is created by the high proportion of nepheline syenite in the recipe.
  18. If the only fault is the elements -- and they are run at the correct voltage -- surely they must be drawing the wrong currents. That's all an element does, turn electricity into heat. So using current-sensing to measure the per-section currents when at full blast gives an end-to-end test of the elements. (Providing that the current sensing is wired correctly.) If the elements -- when fully powered -- are meeting the design specification for power output, then it looks like their duty-cycles aren't correct for at least part of the firing. PS Question for the experts. Do the solid-state relays switch at a sufficiently high frequency for the current sensing to accurately measure the time-averaged current?
  19. >I use zone control and my center elements do not seem to be able to keep up, so the kiln continually stalls out, usually without an error code. >Even in single zone the center section of my 1231 pk fires cooler than the top and bottom. The single-zone result is surprising, as presumably the different element resistances in the top/bottom & centre sections are designed to avoid/reduce temperature differences between sections. [Presumably with caveats about extreme differences in the loading of the sections.] So checking that the various sections are drawing their design power when the kiln is running "flat-out" seems a good first step. The current sensing technology provides a per-section current measurement, and an eyeball check can confirm that the current-sensing loops are indeed round the wires going to the appropriate elements. What currents do you get for the three sections?
  20. Rightly lots of talk about measuring resistances, voltages and currents with a meter, but doesn't this kiln have current sensing technology? https://skutt.com/products-page/ceramic-kilns/km-1231pk/ What does this say about the power going into each section at full blast? And I suspect that it should be pretty easy to eyeball that the current sensors are reading from the right elements.
  21. Good advice, but I think it should be site:community.ceramicartsdaily.org For example google PeterH community.ceramicartsdaily.org gave me 76,400 hits, while google PeterH site:community.ceramicartsdaily.org gave me 186 hits PS Note that these figures vary between users and invocations. A second call produced 957 & 76,400.
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.