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PeterH

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  1. Like
    PeterH reacted to Callie Beller Diesel in Glass frit in glaze   
    If she used glass in her clay, it’s ill advised on her part. I know it doesn’t stop some people if they don’t see anything going wrong immediately, but that doesn’t make it a good idea. The coe of bottle glass or other commonly available glasses including stains and frits used in a hot shop are too distant from that of most pottery clays. I’ve gone on clay/glass rants before. I don’t know that the internet needs another one.
    If you want a similar effect, you could try mixing a clear blue glaze as a paste, crumble it and fire the bits just enough so they sinter. This will keep them from dissolving when you add them to another clear or translucent glaze bucket. They should melt together for a similar effect. The Jungle Jems line does something similar I believe. 
     
     
  2. Like
    PeterH reacted to liambesaw in What glazes does Seth Rogan use?!   
    Looks like layered underglaze which is cut or rubbed off in places
  3. Like
    PeterH reacted to Hulk in Glaze Crazing   
    Delayed crazing may indicate you are closer to a good fit than a fine network of craze lines right out of the kiln, fwiw.
    Ditto on Tony Hansen's website, aye. Here's a repost from another forum thread:
    There are several crazing glaze themed threads on this site; try searching craze, crazed, crazing and read on!
    If you haven't yet found Tony Hansen's website, it's a real treasure, imo (as is this forum, thanks to all the folks who post here); here's his glossary entry on crazing:
      https://digitalfire.com/glossary/crazing
    From there, also see his many several articles on evolving low coe glaze recipes, reformulations, comparison of oxides, glaze chemistry and melting behaviours, oxide interactions, etc., etc.
    You might post the recipe you used, closeup pics of the crazing, and identify the clay as well - for more specific reactions from forum contributors...
    Here's a few results from this forum:
    Deep cracks in the glaze - Clay and Glaze Chemistry - Ceramic Arts Daily Community
    Crazing, Yes, No Or Maybe? - Studio Operations and Making Work - Ceramic Arts Daily Community
    Another Tony Hansen article
    Glaze Crazing (digitalfire.com)
    ...there are many others!
  4. Like
    PeterH got a reaction from Hulk in Glaze Crazing   
    Cracks, especially fresh cracks, can be difficult to see so it's helpful to rub indian ink onto the pot to highlight them. See 1:49 into this video.
    https://youtu.be/VqBkTfGcgmo
    Digitalfire is a good place to start https://digitalfire.com/trouble/glaze+crazing. It also gives several stress-tests https://digitalfire.com/test/iwct
    Once you give some details about you pots (body, glaze, firing) and perhaps a photo I'm sure some friendly expert will be along with more specific advice.
  5. Like
    PeterH reacted to Hulk in Amaco Glazing - cone 5 or 6 and firing help!   
    Hi Lara!
    Your glazing results will very likely be influenced by the clay you are using.
    Typically, glaze fire to bring the clay to full maturity - where sufficient temperature and time (together, "heat work") have vitrified the clay (Maturity (digitalfire.com) - and fully melt the glaze. Also typical, avoid over firing, which can cause a myriad of problems with both the clay and glaze, and under firing, which may leave the clay porous (immature) and glaze not fully melted.
    Please identify the clay(s) you are using, your firing schedule, and post pictures of your glazed work as well as examples of the results you're looking for?
    So much depends on the clay, thickness and size of the work, the surface of the work, how the work is bisque fired, the glaze(s) selected, how the glaze is applied, etc.
    Cone chart indicates just 53F degrees (at 108F rise per hour) between cones five and six, however, a half cone can make a big difference - depends on many factors. I'm firing to cone five now after starting out shooting for cone six. Some of the clays and glazes I'm using tolerate a wider firing range - looks fine at five or six - but two of the clays I use definitely come out better firing a bit cooler and also benefit from a drop and hold.
    Fahrenheit Cone Chart (clay-planet.com)
    Perhaps you are looking at glaze effects that result from layering two or more glazes?
  6. Like
    PeterH reacted to liambesaw in Glaze chemistry   
    Silicon carbide.  The larger the particle size, the more violent the off gassing is.  
  7. Like
    PeterH reacted to Bill Kielb in Replacing potentiometer inside Brent pedal   
    I think you have the answer If you are able to clean it then you should be able to measure it. Pots are rated end to end. To check linear or audio taper set the slide to midpoint and measure wiper to any side. If approximately half, then linear taper. If significantly different than half then audio taper. Very likely linear though. Post and tag the value here for folks in the future.
  8. Like
    PeterH got a reaction from Hulk in Replacing potentiometer inside Brent pedal   
    Look like it's Malatchi CTS Slider Pot 10k Ohm on https://www.surplussales.com//Potentiometers/Slider/Slider-1.html
  9. Like
    PeterH got a reaction from Nehal in What is an Organic Alternative to Wax?   
    You live and learn (slowly). I found ubay a few days ago searching for wax resist, and  suspected that it  is some sort of importing service. It offered several wax resists, but when I looked at  the ordering pages of a few they were all marked This product is restricted in your country. This also seems to be the case for the soy wax you mention.
    Mildly emboldened I revisited the wax resist offers. While most of them are marked restricted some are not, and might be worth trying if the prices are acceptable. 
    https://www.ubuy.com.eg/en/search/index/view/product/B084DNSRVS/s/wax-resist-1-pint/store/store
    https://www.ubuy.com.eg/en/search/index/view/product/B00YAZKEHK/s/wax-on-resist-16oz/store/store
    https://www.ubuy.com.eg/en/search/index/view/product/B0019LPP0E/s/wax-resist-1-pint/store/store
    https://www.ubuy.com.eg/en/search/index/view/product/B001DKJNKE/s/grafix-wm2-white-mask-liquid-frisket-2-ounce/store/store
    https://www.ubuy.com.eg/en/search/index/view/product/B000AP1IR4/s/amaco-rubber-latex-white/store/store
    https://www.ubuy.com.eg/en/search/index/view/product/B0026AA9SK/s/jacquard-colorless-waterbased-resist-clear-2-25-oz/store/store
    https://www.ubuy.com.eg/en/search/index/view/product/B0026AA9S0/s/jacquard-8-oz-water-based-resist-none/store/store
    Anybody care  to nominate the "best" of these for pottery? In case @Nehal fancies trying an order?
    PS @Nehal could you check the soy wax offers and one of the above wax resists offers from inside Egypt?
  10. Like
    PeterH got a reaction from Nehal in What is an Organic Alternative to Wax?   
    You might find something of interest in http://users.skynet.be/russel.fouts/Files/Piece_de_Resistance_Published_Article.pdf
    Rethinking the concept of a resist and what makes it work, or not work, opens up a whole new world of possibilities for resist decoration. My efforts are now entirely directed toward the use of “permeable” resists. Resists that sort of resist and sort of don’t; that block while still allowing some interaction with the surface underneath. Once you understand how resists create barriers, you can broaden your resist decorating “palette” and use their special characteristics in your work.
    I believe that "indian-ink" can also be used as a resist, the Japanese use their own ink in sumi hajiki.
    Sumi Hajiki (墨弾き・墨はじき)
    A decorative technique that uses areas of resist, sumi hajiki literally means "ink repel." Sumi hajiki is created by applying ink under areas of colored pigment. During firing, the ink burns off, which also removes any overlying color and leaves voids in the pigment (Wilson 1995:118). This technique is commonly used to crease veins in leaves.
    Is Sumi ink the same as Indian Ink? India ink usually uses gelatin or shellac for a binder. It looks like sumi-e has just got the glue used to hold together the ink stick. No idea if prepared sumi-e ink has a binder or if it's just water & soot. ... I think the main difference is in the techniques more so than the inks themselves. [I believe that indian-ink's waterproof properties are caused by the presence of shellac soap, which is miscible (rather than soluble) in hot water, but not in cold water. One dispersed in hot water it stays dispersed until the water evaporates.]
  11. Like
    PeterH got a reaction from blackthorn in What is an Organic Alternative to Wax?   
    You might find something of interest in http://users.skynet.be/russel.fouts/Files/Piece_de_Resistance_Published_Article.pdf
    Rethinking the concept of a resist and what makes it work, or not work, opens up a whole new world of possibilities for resist decoration. My efforts are now entirely directed toward the use of “permeable” resists. Resists that sort of resist and sort of don’t; that block while still allowing some interaction with the surface underneath. Once you understand how resists create barriers, you can broaden your resist decorating “palette” and use their special characteristics in your work.
    I believe that "indian-ink" can also be used as a resist, the Japanese use their own ink in sumi hajiki.
    Sumi Hajiki (墨弾き・墨はじき)
    A decorative technique that uses areas of resist, sumi hajiki literally means "ink repel." Sumi hajiki is created by applying ink under areas of colored pigment. During firing, the ink burns off, which also removes any overlying color and leaves voids in the pigment (Wilson 1995:118). This technique is commonly used to crease veins in leaves.
    Is Sumi ink the same as Indian Ink? India ink usually uses gelatin or shellac for a binder. It looks like sumi-e has just got the glue used to hold together the ink stick. No idea if prepared sumi-e ink has a binder or if it's just water & soot. ... I think the main difference is in the techniques more so than the inks themselves. [I believe that indian-ink's waterproof properties are caused by the presence of shellac soap, which is miscible (rather than soluble) in hot water, but not in cold water. One dispersed in hot water it stays dispersed until the water evaporates.]
  12. Like
    PeterH reacted to Sorcery in Mixing local earthenware and stoneware   
    I have been experimenting with 3 different local clays like this. 
    I reckon the #1 underestimation is the longer bisque times in oxidation to burn out what is likely a higher impurities content. I have a photo here somewhere of a clay much less bloated with a longer burnout.
    I've found most of the best effects of local materials are most easily had by using it to decorate the outside. For a slab builder like me, this means ribbing sand into the outside, using the clay as slip glaze, or carving depressions to rib the clay into. The benefit/hassle ratio here is 90/10.
    Using it inside the clay, for an understandable use of local materials, is mathematically very unsound for finances, depending on the clay and situation of course. For my situation and clay, the benefit/hassle ratio is 10/90.
    I don't believe this changes until your local clay is good stoneware and your closest supplier.....isn't.
    Sorce
     
  13. Like
    PeterH reacted to Bill Kielb in Analog pyrometer wiring?   
    Most likely the meter or it’s not built for a type K thermocouple. Odd! Anyway if you have a volt meter just test the thermocouple. It will read in millivolts (Dcv). You can confirm it rises just by warming with your hand once connected to your voltmeter or even torch the thermocouple a bit to get it to rise. You actually might try that hooked to the pyrometer meter you have,  just in case it’s not very responsive till you get up to a few hundred degrees.
    It takes such a small amount of voltage to operate an analog meter like you have which means  they are usually very sensitive to vibration. The pointer generally freely travels so bumping or shaking it lightly usually results in significant needle deflection. The return spring on that meter should be super light.
    The result is usually they lock the needle down for shipping so also make sure the zero adjust has not been preset to limit needle movement during shipping. Other than that, if you can do the voltmeter test it will confirm if the thermocouple is fine and the analog meter you have is stuck or bad. Generally bad thermocouples are easy to spot so hopefully the analog meter you have is locked down or is just not sensitive at low temps.
    Even cheap digitals have a big advantage in accuracy and mechanical longevity. Analog meters are not common anymore.
  14. Like
    PeterH reacted to tinbucket in Alumina (?) paper clay sheets   
    You may find this helpful. Although it is for a different application (I think?) the material is basically the same as Keraflex. Someone at Alfred University did some research on "tape casting" which is basically a ceramic matrix spread into a thin sheet using glycerine and PVA (Elmers) glue. A thin, flexible, unfired sheet of clay. Although the set up is relatively simple I think it will require some research and testing - the only advantages I see over Keraflex being availability and cost (although time is money). Good luck! Very curious what you plan on making with it. 
     
    https://static1.squarespace.com/static/527ac372e4b0d4e47bb0e554/t/527fd23fe4b0f7fd724aba83/1384108607291/tape+casting.pdf
    The student "cookbooks" in this second link also have some documentation of students' tests with tape casting. I don't remember where, you'll have to scan through and find them. The Alfred Grinding Room website is an excellent resource for other alternative ceramic processes as well. 
     
    http://www.alfredgrindingroom.com/recipes
  15. Like
    PeterH reacted to Callie Beller Diesel in Using Stains mixed only with water   
    If you want the simplest and easiest homemade underglaze recipe, mix your stain with equal parts of EPK and frit. So that’s a 1:1:1 ratio.  Bonus points if the frit you’re using is also one of the fluxes in your glaze, but it will all work. 
     
    reasons for those ingredients: 
    The frit helps bind the sometimes very refractory stains to the pot, and the clay is an extender. Stains can be expensive, so the clay is just there to extend the recipe and help make it more brushable. Edited to add: You will still get a saturated colour if you keep the clay to this level. 
     
    I have used gerstley borate to mix stains in. It makes a preferable brushing medium, but it will also alter the colour of some stains, so test a bit first. 
  16. Like
    PeterH got a reaction from Babs in What is the best posture for sitting at the potter's wheel?   
    A couple more variations on the theme:
    In the Studio: Get Up, Stand Up https://ceramicartsnetwork.org/pottery-making-illustrated/article/get-up-stand-up/
    Ergonomic Throwing https://robertcomptonpottery.com/index.php/vermont-studio/forming-techniques-2/forming-methods-wheels/
    ... I was interested/surprised by an idea in the latter

  17. Like
    PeterH got a reaction from Magnolia Mud Research in What is the best posture for sitting at the potter's wheel?   
    A couple more variations on the theme:
    In the Studio: Get Up, Stand Up https://ceramicartsnetwork.org/pottery-making-illustrated/article/get-up-stand-up/
    Ergonomic Throwing https://robertcomptonpottery.com/index.php/vermont-studio/forming-techniques-2/forming-methods-wheels/
    ... I was interested/surprised by an idea in the latter

  18. Like
    PeterH got a reaction from Babs in Kiln “noodles”   
    @Babs Correct me if I'm wrong, but Fibre Rigidiser might be a good search term.
  19. Like
    PeterH got a reaction from Angela D in Kiln “noodles”   
    @Babs Correct me if I'm wrong, but Fibre Rigidiser might be a good search term.
  20. Like
    PeterH got a reaction from Angela D in Kiln “noodles”   
    There are some manuals at https://paragonweb.com/support/instruction-manuals/
     
    At least this one Duncan EA-092 and EA-122 Instruction Manual LX855 shows a fibre interior

  21. Like
    PeterH reacted to liambesaw in What do we know about Iron Chromate?   
    Chromate is hexavalent chromium,  iron chromite is not.  They are not synonymous, that's the confusion I am referring to above. 
    Iron chromate, highly toxic, water soluble, carcinogen.  
    Iron chromite, slightly toxic, insoluble, not carcinogen.
  22. Like
    PeterH reacted to liambesaw in Is this crawling?   
    Pinholing, high viscosity melt, probably due to the magnesium content.  With a more fluid melt the bubbles may heal themselves, but I've found the manganese they use in those speckled bodies gasses off a LOT and late in the firing too.  Need a glaze that's less viscous in my opinion
  23. Like
    PeterH got a reaction from Hulk in Clay analysis, where to go?   
    Nope, try this   https://tinyurl.com/y3rztakd
    The two papers on Norway are at
    https://njg.geologi.no/images/NJG_articles/NGT_52_4_335-369.pdf
    https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.606.1395&rep=rep1&type=pdf
     
    PS If there are still problems I'll send google search strings
  24. Like
    PeterH got a reaction from Hulk in Flocculation and specific gravity   
    You may find this of interest. Adjusting Glazes for Application by Pete Pinnell https://www.claytimes.com/articles/glazeadjusting.html
    My reading is that you need to re-flocculate a glaze if you have deflocculated it!
    In Pete's words
    So why would anyone deflocculate a glaze? Well, most of the time it's not done on purpose. The alkali can dissolve out into the water from some of our materials. Yes, we try to use only insoluble materials in our glazes (i.e. materials that will not dissolve in water), but in practice some of our materials do exhibit some solubility. The amount of solubility is very small, but since the clay content in most glazes is also small (often less than 10%), even a little solubility is enough. Some of the common materials that can cause this are wood ash, soda feldspar, nepheline syenite, many common frits, and lithium carbonate. I like to think of these as our problem children: they have qualities that make us want to keep them, but they can still make our lives miserable!
  25. Like
    PeterH reacted to Min in Flocculation and specific gravity   
    I used to use a graduated cylinder when testing specific gravity but found using a 60 ml syringe is faster. It does hold a little back when you empty it so I draw up some water first, plunge it out then tare out the scale with the syringe on it. Then I draw up the glaze, bring it to the 50 ml  line and rinse off any glaze that gets on the outside of the syringe, weigh it then double the amount. I find it less messy than using a graduated cylinder plus it's faster. I have a few I bought super inexpensively from Aliexpress. (which should be called Alislow as it takes forever for stuff to get here)

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