PeterH
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Posts posted by PeterH
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Thin pickings.
If you have access to Clay Times Magazine Volume 16 • Issue 86 this article might be of interest and/or provide pointers.
... index and some pages (but not the article) in https://issuu.com/claytimes/docs/claytimesbackissuesbernadettecurran... my interest was based on
Description of the show in
https://taradawley.wordpress.com/2010/02/03/1053/
... but couldn't find anything significant therePS Stumbled across this "what's in a name" paper
American Shino : A Case Study of Cultural Borrowing in the World of Traditional Ceramics
https://konan-u.repo.nii.ac.jp/?action=repository_action_common_download&item_id=4047&item_no=1&attribute_id=22&file_no=1
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Some ideas on glazing non-porous bodies in this thread.
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21 minutes ago, cemoore said:
Thanks Peter, I read the links and will check out bone china. Sounds like a material that's outside my current skill level (everything is at the moment with slip casting), but maybe aspirational. I like the idea of being able to glaze after grinding and knowing there won't be discernible shrinkage.
I was definitely NOT suggesting that you used bone china, it warps/slumps too much. Just using it as the classical example of high-bisque low-glost approach. If you do read up on it I would concentrate on how they get the glaze to stick to a non-porous body: pre-heating, additives, ...?
Will you need the puck to be glazed on all surfaces? If so using stilts is one option, another might be to glaze the "bottom" in an additional lower-fired glazing.
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Casting bodies don't need to be very plastic, and can have comparatively low shrinkage.
https://digitalfire.com/glossary/slip+casting
Slip cast ware can dry-shrink as little as 1.5% (compared to 6%-8% for plastic stoneware bodies).https://www.potterycrafts.co.uk/Products/pottery-powdered-clays/P3101
Shrinkage (w-d) 2 - 4% & Shrinkage (d-f) 6 - 8%So maybe 4% for bisque to fully fired?
However you could high-fire to maturity, grind, and then either high or low-fire to glaze -- so zero shrinkage. Bone-china is traditionally fired high-bisque low-glost (it needs to be supported when fired to maturity).
Glazing a mature body presents problems, as it isn't porous, but is probably doable (AFAIK industrially various additives are used).
PS Solid casting is possible, unless the gradual build-up of clay obstructs the inflow of fresh slip. A hockey puck seems a pretty undemanding shape.
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Just or the record, there are several 3D printing pages at digitalfire.
3D Printing a Clay Cookie Cutter-Stamper https://digitalfire.com/video/3d+printing+a+clay+cookie+cutter-stamper
3D-Printing https://digitalfire.com/glossary/3d-printing
3D Design https://digitalfire.com/glossary/3d+design
3D Printer https://digitalfire.com/glossary/3d+printer
Project: 2019 Jiggering-Casting Project https://digitalfire.com/project/15 -
1 hour ago, TroyMorris said:
Hi everybody, I was ready to place an order for a pricey baking stone for bread/cookies/pizza until I realized (DUH!!) that they are made of clay!! So, should I be able to make one? I have a couple of inquiries:
- What kind of clay is it? I have Laguna 55 cone 6 white clay, Laguna 66 cone 6 handbuilding clay, a cone 10 woodfire clay, and I believe I have a cone 10 B. Combine with grog.
- I'm still not very good at producing wide flat things, so can I roll out clay with my roller and then cut it to the right shape?A search for "pizza stone" or something similar will throw up a lot of hits.
As you will want to include archived threads in your search, best to use a browser search something like
site:community.ceramicartsdaily.org baking stone... which found the following threads, with a fairly common theme - buy a kiln shelf, if only because you cannot get a suitable clay.
Starting with an eerily similar question to your own.
- Rae Reich, Kelly in AK, Min and 1 other
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4
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May I suggest that you make a few more birds, a little practice/experimentation goes a long way.
Then maybe try for a hollow bird
How to make a hollow bird form using thumb pots... Make a small through hole with a skewer to let any steam generated during firing escape.
You can make some bowl-ish items by draping thin
classclay slabs over a balloon.
e.g. clay over a balloon https://www.pinterest.co.uk/jazzdd76/clay-over-a-balloon/
... which also mentions a few projects, such as
More balloon ideas at Pottery Ballon Technique https://www.pinterest.ca/black3200/pottery-ballon-technique/
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35 minutes ago, Min said:
Hi Maria and welcome to the forum!
Is this the Turner's White recipe you used? If it is did you include the zirconium opacifier both in the past and with this current batch?
Article on Turner's white with some examples
It Slices, It Dices! Some Simple Glaze Tests Reveal a Ceramic Glaze That Can Do it All (well, almost)
https://ceramicartsnetwork.org/daily/article/It-Slices-It-Dices-Some-Simple-Glaze-Tests-Reveal-a-Ceramic-Glaze-That-Can-Do-it-All-well-almost
.. I notice it says under Colour Development
The second part of our project was to use Turner's White as a base, but just exclude the Zircopax (an opacifier). -
... and another method for reducing texture on your 3D printed master, spray paint.
See Smooth PLA | No Sanding https://youtu.be/rn4edNztaPU
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Speculation ... based on plaster apparently left adhering to your 3D printed mould.
Could some of your issues be caused by the "texture" generated by the 3D printing process. Are you are pulling the plaster out of the mould "against the grain" rather than normal to it at the points retaining plaster. (Is the issue texture-scale undercuts rather than PVA/plaster adhesion?)
If that's the case, these seem to be some of the ways other people have used to get a smoother/less-textured surface.
Sanding 3D Prints: How to Sand PLA & More
https://all3dp.com/2/sanding-3d-print-pla/
... includes How to Print Smooth PartsPLA Smoothing: How to Smooth 3D Prints
https://all3dp.com/2/pla-smoothing-a-beginner-s-guide/UK 3D printing epoxy ads
https://tinyurl.com/ebvhn2ed
https://tinyurl.com/2jvcuvn3PS The sacrificial mould technique would probably tend to remove the PLA from the plaster in a direction more normal to the local plaster surface and its texture, which might reduce damage. in some circumstances -- but I don't think it would work well at the edges of the handle.
PPS At one point I found an article advising that auto-restart (after power failure) was turned off to get a smoother 3D print, but I cannot find it again.
... this seems to mention the issue.
Power Loss Recovery Might Make 3D-Printed Blobs
https://hackaday.com/2022/10/10/power-loss-recovery-might-make-3d-printed-blobs/ -
I also found this forum because general searches found some very interesting postings on it.
When I want to use a general browser (mine is google) I default to using site:community.ceramicartsdaily.org
PS Just for interest I tried three google searches
"red clay" and community.ceramicartsdaily
"red clay" community.ceramicartsdaily
"red clay" site:community.ceramicartsdaily.orgWhich returned 12,700, 15,000 & 594 results respectively. (The order, and possibly the number, of results may/will-be influenced by my previous search history.)
Repeating the searches a few minutes later I got 13,400, 15,400 & 757 results.
Just reporting the number of results, not judging their quality.
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Tony Hansen strikes again.
in https://digitalfire.com/picture/2463
The incredible utility of 3D printing master handle moldsAs a parting-agent I use Murphy's Oil Soap on the 3D-printed PLA mold, this makes it fairly easy to extract the freshly-cast plaster molds (the sidewalls have a draft of about 5 degrees).
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42 minutes ago, High Bridge Pottery said:
Thanks Peter, I wonder what plastic they are using, maybe PETG as they don't seem apply anything to help the plaster release. I have done some printing with PETG but it's not as easy to print with as PLA.
Why not ask her https://www.instructables.com/member/Charlotte_J/instructables/
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51 minutes ago, High Bridge Pottery said:
I have been 3D printing some forms to cast in plaster but found it time consuming setting up cottle boards every time I wanted a new mold. Started working on getting a form that I could pour plaster directly into to make the mold.
I was reminded of a different approach to the same 3D printing idea. It used sacrificial 3D prints, and produced moulds with minimal excess plaster.
3D Printing a Mold for a Slipcasting Mold
https://www.instructables.com/3D-Printing-a-Mold-for-a-Mold/
Obviously horses for courses, but maybe something for your notebook.
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For non-brits, the UK 13A ring main is described in
http://wiki.diyfaq.org.uk/index.php/Ring_circuitThe ring circuit and BS 1363 plug and socket system were developed in Britiain during 1942-1947.(ref 1) They are commonly used in the United Kingdom, and to a lesser extent in the Republic of Ireland.
The ring circuit came about because Britain had to embark on a massive rebuilding programme following World War II.(ref 2). There was an acute shortage of copper, and it was necessary to come up with a scheme that used less copper than would normally be the case. The scheme was specified to use socket outlets with 13 Amp fused plugs.
...
The ring circuit was devised during a time of copper shortage to allow two 3kW heaters to be used in any two locations and to allow some power to small appliances, and to keep total copper use low.
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To measure the resistance you could measure it at the switch (turned off, maybe power off as well), or remove the connections from the switch and measure via the leads.
You can measure current with a clamp ammeter, although you might need to jury-rig a connection to do so. Just one of the power leads (live or neutral) has to be inside the clamp.
eg https://www.ebay.co.uk/sch/i.html?_from=R40&_nkw=clamp+ammeter&_sacat=0&_sop=15
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42 minutes ago, High Bridge Pottery said:
so it seems like they may have upgraded the elements to draw 2.5kw.
I've been thinking along similar lines, but wondering if they are 220v elements run at 240v.
As power is proportional to V^2, this would give (240/220)^2*2000 ~2380w at 240v.
... probably not good for element life, so your series comment seems even more appropriate.
PS
220v would give 2000w with a resistance of 220^2/2000 = 24.6 ohms. So if the current resistance is 26 ohms that's about 100*(26/24.6-1) ~ 5.6% gain over time. -
Can you post a picture of the kiln plate?
PS
I haven't yet found anything on CTL-17s on the net, but many of the CTLs seem to exist in 220v & 240v versions.The CTL28 is listed as a 3KW kiln for 220v & 240v operation in https://www.cromartiehobbycraft.co.uk/files/Kiln Downloads/CTL Range Leaflet (1st).pdf
But both 3.0kw and 3.3kw versions of the elements are offered here https://tinyurl.com/58knhuwy
... other models seem to have an optional N suffix, for which a higher wattage element is sold.Might be worth asking Cromartie what they think the resistance of your element(s) should be.
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Thread on ITC coatings.
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A couple of minor points if you are still trying to increase the crazing.
1) Always ink-up (part of) your test-tiles. It can sometimes be hard to see the true extent of the crazing. It also gives you a better idea of the number of cracks which occur after the initial inking.an example from Digitalfire
2) I understand that glaze programs are not too accurate at estimating the absolute COE of a glaze, but they are quite good at estimating the change to the COE that small change to the recipe/chemistry will make. So maybe you are reaching the point where they might be useful.
See Using Calculation to Fit a Glaze in https://digitalfire.com/article/understanding+thermal+expansion+in+ceramic+glazes -
It might be interesting to try a crazing test on your test-tiles, such as
IWCT - 300F:Ice Water Crazing Test
https://digitalfire.com/test/iwct
If only to judge the effect of any changes you make to the recipe/firing. -
For those trying to offer a match
https://www.potterycrafts.co.uk/Products/003500420073/CY120PS It seems to be selling it at half price in the UK (stock clearance?).
Duncan Courtyard Harvest Plains - 4oz £3.20 (exc VAT)
Promotional Price - Save £3.19 (Usually £6.39)https://www.potterycrafts.co.uk/delivery_rates
Rest of World Orders:
Orders Under 2kg in Weight: Carriage £ 24.99 -
If this reference is representative "vivid" manganese purples may be fairly thin on the ground.
A Plethora of Purple: Glaze Recipes for Earthenware, Stoneware and Porcelain
https://ceramicartsnetwork.org/daily/article/A-Plethora-of-Purple-Glaze-Recipes-for-Earthenware-Stoneware-and-PorcelainThe manganese containing purples illustrated are:
But here are well-lit examples of a very dark glaze with character from https://gotheborg.com/glossary/aubergine.shtml
... so maybe it's worth trying "aubergine" or "eggplant" as a search term.
There is an aubergine glaze recipe without a picture at:
... As reported elsewhere closed threads are not searched by this sites search engine. So such postings can only be found using a search engine such as google. In this case searching for
"aubergine gloss glaze" site:community.ceramicartsdaily.org -
30 minutes ago, Kelly in AK said:
Try searching for “manganese violet glaze recipe” or “manganese purple glaze recipe.” to start with and see what you find.
... but be aware that "manganese violet" is also the name of an organic artists pigment (i.e. low temperature only?).
https://en.wikipedia.org/wiki/Manganese_violet- Kelly in AK and Rae Reich
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2
using paper mache technique with clay
in Studio Operations and Making Work
Posted
The clay will shrink as it dries, which can be problem if the balloon doesn't slowly leak/shrink.
I found that a non-intrusive way to let a little air out of a balloon was:
- put a strip of sellotape on an accessible part of the balloon
- rub to get a good sellotape/rubber seal
- prick through the sellotape & balloon with a needle
- let some air out
- reseal the balloon with another strip of sellotape over the first
Try it on a spare balloon first.