PeterH
-
Posts
1,481 -
Joined
-
Last visited
Content Type
Profiles
Forums
Gallery
Posts posted by PeterH
-
-
10 hours ago, neilestrick said:
My students use a fair amount of Standard 266
Two googles that might be worth trying, and an example hit from both.
site:glazy.org "standard 266"
https://glazy.org/recipes/22329
Shows a base glaze with several different colourants.
"standard 266" glaze selecting the "images" option
https://www.flickr.com/photos/133519868@N03/32484512766
Finally ..
Glazy has an Alfred Blue at https://glazy.org/recipes/217896
... and the referenced "University of Maryland Glazes" article is on p32 of ...
https://ceramicartsnetwork.org/docs/default-source/uploadedfiles/wp-content/uploads/sites/6/2015/06/ceramics-monthly-feb80-cei0280d.pdf -
Maybe loosely relevant.
@ChenowethArts has previously posted on ocarinas, although hasn't visited here since Jan '22
...his website seems to still be online http://www.paulchenoweth.com/ but dates seem to be '21
... contact page (was?) https://www.paulchenoweth.com/?page_id=718 -
-
22 minutes ago, Crooked Lawyer Potter said:
What are the characteristics of a liner glaze? Does the term simply denote its position and function in the interior or are there certain qualities distinct from regular glazes?
https://digitalfire.com/glossary/liner+glaze Liner Glaze
The term "liner glaze" refers to two things. First, it is a technique (links below), where the inside and outside of a piece have different glazes that meet at the rim. Second, it refers to the practice of choosing a glaze for the inside food surfaces of utilitarian ware based more on its durability and resistance to leaching, running, crawling, blistering and crazing (problems common with reactive glazes). Glossy whites, transparents or modestly colored glazes are most common as liners. Liner glazes can have other practical purposes also. An example is their use in combination with intensely colored or variegated glazes, such are often runny and form a lake in the bottoms of vessels - this can lead to glaze compression failure.
... -
10 hours ago, Rockhopper said:
Have never tried it, but remember reading somewhere in this forum that skunk hair works quite well. Don't recall who posted it, but they mentioned keeping a bag and gloves in their car, so they could collect such hair from road-kill when the opportunity arose.
Mark C in this thread?
-
17 minutes ago, Pres said:
Google searches on Japanese pottery throwing methods do bring up quite a bit of information. You may find some Utube videos that will help you also. Years ago, I was having problems with S cracks in the bottom of small vessels off of the hump. . a utube video showed me to make a pancake on the hump and then bring up the sides and then pull the walls. This was a Japanese method.best,
Pres
A good example of the type of video you might hope to find, which also illustrates a potential problem. Pres explains the technique works because it helps align the clay particles in a good way, but this is not obvious from seeing the video. You really want to know both how and why, although seeing how can help you discover why.
-
On 2/6/2024 at 4:03 PM, Callie Beller Diesel said:
I’ll tag @PeterH
Firstly I think Callie is right that you may have more success looking for videos. The short video format might favour highlighting little tips and tricks. I suspect that "the East" may tend towards a culture of immersion in the process rather than highlighting details of the process.
Sorry, couldn't find any books, but a few minor hits and follow-on questions on the pros and cons of:
- types of wheel: electric, kick & banding
- throwing vs trimming
- asking Denicehttps://www.benthampottery.com/throwing-pots-left-handed/
Throwing Pots Left Handed
...
Throwing is a two handed process. In Japan they spin the wheel the other way and that is nothing to do with right or left handedness. Just carry on as normal. The psychology is interesting. Potentially the focus may be on the inside instead of the outside of the pot which affects the results in an interesting way
...
I’ve been throwing for 43 years, teaching for 20: left handed potters throwing counter clockwise have the advantage, as the left hand is inside, and easier to control the form that way.
...
I am left handed and learned right handed. All you are doing is having the strong hand inside the form like they do in Japan. Handedness isn’t important on an electric non-kick wheel.
...
I find that the issue isn’t often with throwing but with trimming. Most people can learn to throw either way, but trimming is a whole other story. I teach with my wheel turning clockwise and just explain and demonstrate the different hand positions
...
Given that for most of us our strongest hand is also the one with the finest control I'm not even sure that having the same spin for both throwing and trimming is necessarily optimum. (Although constantly switching may outweigh any advantages.)A couple of videos from
Trimming Mugs/bowls Without The Wheel
https://community.ceramicartsdaily.org/topic/13230-trimming-mugsbowls-without-the-wheel/?do=findComment&comment=97096
Pedantically a misnomer, as both videos show trimming on a wheel-head, but using it like a banding-wheel.
https://youtu.be/f64J6C48ZSo
https://youtu.be/3mmJwnhPivICouldn't find anything significant on electrified kick wheels, but did find this.
Hopefully technology is advancing towards a combined electric/kick wheel where you only need to kick where there are positive artistic advantages in doing so. As long-term kick-wheel use could be hard on the body: although maybe artistically good for the soul.
So my only conclusion is you consider which wheel/spin combination works "best" for each of your activities: such as
- opening-out
- main forming
- finishing-off
- trimming.Is there a clear winner, or is some sort of mixed strategy better?
@Denice any comments? You obviously have some regrets.
-
30 minutes ago, mr_glazy_man said:
I’m so glad you posted those links, I’m hung up on exactly this as well. If decomposition happens at 320C, I would certainly not be having the issues I’m having because my high fluxed (read: high boron) glazes begin to melt at around 750-800C.
I'm certainly out of my depth here.
Before I'd read the Digitalfire entries I would have readily accepted your last sentence. Now I'd like to see some sort of "acid test", as I wouldn't have anticipated either of these results.
https://digitalfire.com/picture/sagpedasyt
Switching copper carbonate for copper oxide in a fluid glaze
The copper oxide recipe is not bubbling any less even though copper oxide does not gas.https://digitalfire.com/picture/2387
This flow tester proves the colorant is not fluxing or bubbling the glaze
Another observation: I was suspicious that the micro-bubbles in the glass matrix were coming from the copper carbonate gassing during firing. But not so, as you can see, the flowThat is, testing the base glaze on its own or with the addition of non-outgassing copper oxide.
Maybe I'll be less paranoid in a few days time ...
-
8 hours ago, mr_glazy_man said:
As a matter of curiosity, what temperature does copper typically finish its offgassing?
While waiting for the experts to arrive ... I tried to find a decomposition vs temperature graph and went where the links led me.
Digitalfire contains a large amount of somewhat confusing information under both copper carbonate and copper carbonate basic (which is what is sold).
https://digitalfire.com/material/copper+carbonate
https://digitalfire.com/material/copper+carbonate+basicThe latter contains the most confusing decomposition graph I've seen. Not because of technical issues, just because its difficult to distinguish between the two lines presented.
Picking up on the annotation "At 320C the remaining product is CO and all H2O and CO2 are driven off in one step" I found this simpler graph.
https://www.researchgate.net/figure/TG-curve-of-copper-carbonate-NPs-sample-mass-30mg-heating-rate-10C-min-nitrogen_fig7_324064239
Which pretty unambiguously indicates that the copper carbonate decomposition/outgassing happens before 320C!Some of the items in the Digitalfire pages mentioned earlier may help make sense of the fact that glaze bubbling seems to be happening at temperature far above the decomposition point of copper carbonate, in particular
https://digitalfire.com/picture/sagpedasyt
The copper oxide recipe is not bubbling any less even though copper oxide does not gas.https://digitalfire.com/picture/1665
The top base glaze has just enough melt fluidity to produce a brilliant transparent (without colorant additions). However it does not have enough fluidity to pass the bubbles and heal over from the decomposition of this added copper carbonate! Why is lower glaze passing the bubbles? How can it melt better yet have 65% less boron? How can it not be crazing when the COE calculates to 7.7 (vs. 6.4)? First, it has 40% less Al2O3 and SiO2 (which normally stiffen the melt). Second, it has higher flux content that is more diversified (it adds two new ones: SrO, ZnO). That zinc is a key to why it is melting so well and why it starts melting later (enabling unimpeded gas escape until then). It also benefits from the mixed-oxide-effect, the diversity itself improves the melt. And the crazing? The ZnO obviously pushes the COE down disproportionately to its percentage.
... which gives a different rationale for adding zinc.
-
4 hours ago, Min said:
there is a glaze called Folk Art Guild White
https://glazy.org/recipes/67304
Which seems to react to the pots texture by "braking" reddish-brown on the high points.Here is close-up of another Bertoncello piece.
https://antiques-international.ch/product/bertoncello-ceramic-vase-square-shape-with-two-hole-handles-by-roberto-rigon-italy/
I've certainly not got a better idea of what's happening, but I really don't understand how that pattern is formed.If it is the result of firing single layer of glaze over a smooth pot I'm really baffled.
[Unless it's something really strange like a white crackle glaze leaving behind finger-wipe style colouration.]
-
On 2/5/2024 at 9:42 PM, Crooked Lawyer Potter said:
The defects do not appear anywhere except in the interior of mugs or glasses.
Are there any differences in glaze application methods/timing between your mugs/glasses and the other pots?
-
-
11 hours ago, Crooked Lawyer Potter said:
I'm thinking it must be related to the different conditions that arise in the tight confines of the mugs interior (higher heat, perhaps?).
The "higher heat" idea was explored in this thread
... but I wouldn't be surprised if your problem was related to differences in inside and outside glaze application.
-
On 2/4/2024 at 7:14 AM, PaulaD said:
First time using this site. I made the mistake of buying the largest size of Palladium 5 gallons because I was brand new to dipping and never expected issues! Even though I bought it premade
A little googling that might help somebody else address the "craft" issues.
Can you clarify exactly what you bought, preferably including a link to the supplier/product.
To my surprise I did find adverts for dry-mix for a dipping glaze (in addition to zillions of adverts for the painting glaze).
https://s3.amazonaws.com/amacobrent/lesson_plan_files/attachments
... which includes
Mixing instructions (initial and re-mixing before use) in above reference, and as videos in
https://www.amaco.com/clay_how_tos/216The dry-mix advert was for 25lb of powder which by my (unchecked) calculations should make about 4.48 US gallons of glaze.
... assuming the density of the powder is 2.6, as suggested in https://wiki.glazy.org/t/brongniarts-formula/780.htmlIt would be nice to check the specific gravity of your glaze.
https://ceramicartsnetwork.org/ceramics-monthly/ceramics-monthly-article/tips-and-tools-specific-gravity#
As Jeff mentioned the appearance of this glaze is affected by its thickness.
https://s3.amazonaws.com/amacobrent/lesson_plan_files/attachments
... contains guarded advice on layering, so double/long dipping to thicken the glaze might be possible.
-
52 minutes ago, Hulk said:
From John Britt's "Mesh Size" article linked to Ceramic Arts Daily, 200 mesh used to be the glaze standard (fifty years ago), "Using 200-mesh silica now may be closer to using 325 mesh back in the day." and 325 will melt easier.
https://ceramicartsnetwork.org/ceramic-recipes/recipe/Mesh-Size#
-
How dry/firm was your clay? Are we talking about applying a firm-ish slab to a drape/press mould or building up wettish clay in some sort of "slip" mould?
If you abandon this first effort make sure you find out where & how it's sticking (e.g is it surface to surface or some sort of shape interlocking).
PS Googling pottery mold styrofoam turns up lots ideas to compare-and-contrast with your technique, for example
Using a Common Styrofoam Mold for a Platter, with Stoneware Slip over Kentucky Brown Bear Clay.
https://www.youtube.com/watch?v=O0yB3Uv3-pU
... a fairly arbitrary choice, the slab looks overdry to me but I cannot imagine it sticking in that mould. -
16 hours ago, Freya said:
@HulkThank you so much for the inputs! I will definitely do some exploration on the public education resources in Bay Area.
+1
There are also some very useful sites on the web, e.g. https://digitalfire.com
Just picking up on your reference to lead (and I agree it's best not used).
"Safe" a somewhat conditional term.
- The magnificent lead-glazed wall tiles that were still around in older buildings in the 60's would still - IMHO- be quite safe. (Hard to misuse on a dry vertical surface subject to minimal contact.)
- OTOH I remember reading of a lead glazed milk jug (which was probably quite safe to use for milk). But the owners squeezed orange juice into it every evening and left it in the fridge overnight to serve with breakfast! Definitely risky. But how do you know what your friends/customers are going to do with your pots?Some craft potters choose to use "liner" glazes for surfaces likely to come into contact with food.
https://digitalfire.com/glossary/liner+glaze
Liner-glazing is a very good way to assure that your ware has a durable and leach resistant surface. It also signals customers that you care about this.https://digitalfire.com/glossary/lead+in+ceramic+glazes
Lead is a melter in ceramic glazes and performs exceptionally well and must be misused to be toxic. It is also now environmentally pervasive. It is toxic and cumulative at any level of exposure.
... and had a history of frequent misuse, hence the [slightly over] reaction to its use. -
Years ago I moved from a soft water area (Liverpool) to a hard water area (Essex), and my skin stopped wrinkling when I had a long baths. (Also I needed to use more soap, as hard water reduces its effectiveness.)
A suggestion that the effects of moving from hard water to soft may be self-correcting over time.
https://kidshealth.org/en/kids/wrinkly-fingers.htmlI suppose you might try experimenting with:
- pre-exposure skin/barrier creams
- slightly hardening the water you use for throwing (slightly because it may effect the clay)
https://sciencing.com/make-hard-water-8191733.html
https://www.usgs.gov/special-topics/water-science-school/science/hardness-water
General guidelines for classification of waters are: 0 to 60 mg/L (milligrams per liter) as calcium carbonate is classified as soft; 61 to 120 mg/L as moderately hard; 121 to 180 mg/L as hard; and more than 180 mg/L as very hard.
Atlanta refs to confirm your suspicions about water hardness.https://www.atlantisplumbing.com/articles/city-water-vs-well-water/
City Water Vs. Well Water
2. Generally speaking, well water is hard water so a water softener is recommended for homes that use well water.https://www.hydroflow-usa.com/georgia-water-hardness
Georgia water is considered soft water. The average water hardness for the Georgia resident is around 60 PPM. Atlanta, the most populous Georgia city has a water hardness level of 21 PPM which according to USGS water hardness measures is very soft.PS In this context mg/L = mg/kg = PPM
-
Re: memory in clay, just remembered this example.
Control of desiccation crack pattern using memory effect of clay paste
https://www.gruppofrattura.it/ocs/index.php/esis/ECF18/paper/viewFile/6064/1949
-
15 hours ago, Min said:
I looked up the Lavafleck and see that it has a firing range of 1200 C - 1270C. Clay is at its strongest when fired to maturity so if possible I would suggest raising the 1240C that you currently fire at. (and adjusting glazes as necessary)
+1
I found a potclays-clay-analysis.pdf file on the https://www.bathpotters.co.uk/ site.
https://www.bathpotters.co.uk/userfiles/file/potclays-clay-analysis.pdf
...which gives vitrification range 1250-1280 & firing range 1200-1280PS Finally found it on the Potclays site.
Click download file in the Clay Analyses box on
https://www.potclays.co.uk/Technical-Information -
On 1/24/2024 at 12:10 AM, s6x said:
I know there are glazes that will crackle, but I would like to have some serious, deep crackling, like in this piece, which I assume was achieved by adding slip at some point... but how do you do this in a manner that will make the slip seriously crack, but not fall off?
I like how the surface of the piece in the photo is red on the bottom, but the top crackling layer is white. Was this effect achieved by manually painting the cracks? or is it possible to apply a red glaze first, before a white slip is applied on top?
My first impression that it's not a normal crack pattern, which are often well described by
Hierarchical crack pattern as formed by successive domain divisions Pt 1
https://www.researchgate.net/publication/235540544_Hierarchical_crack_pattern_as_formed_by_successive_domain_divisions_I_Temporal_and_geometrical_hierarchy
Which seem to have a family resemblance to many crackle glazes, and this crackle slip
https://glazy.org/recipes/56903
... which isn't looking too like Aneta Regel's work to me.
Perhaps this is because there are "large" grains inside the shrinking "slip", causing both local "hot-spots" in the tension and impeding the free propogation of the crack within the mixture. -
On 1/22/2024 at 4:14 PM, Simon77 said:
Is it possible to slip cast in a waste mold?
If by waste mold you mean a sculptor's mold that cannot be removed from the casting without being destroyed ...
I think the answer has to be no, as the fragile casting would not survive any process that required the the mold to be destroyed to free it.It may be possible to make a reusable multi-part slip-casting mold from the original clay master. If this can be done without undercuts which would prevent freeing the casting from the mold.
>The thing is that i have a larger sculpture ...
... although large slip-filled molds are heavy and must retain their form during man-handling: e.g. use of natches for registration, holding things firmly together with straps, ...
-
Is the video you mention the Ceramic Review ""masterclass"?
The accompanying article is at
https://www.ceramicreview.com/articles/material-beauty-2/PS A couple of quotes I found interesting.
https://tlmagazine.com/nomad-vibrant-colours-and-playfulness/
Stone (both presented and represented in her work) makes an important contribution to the materiality of Regel’s artistic practice. Her technique of mixing porcelain with gravel, placing stones into the clay, and subsequently allowing the clay to shrink and crack around the rock inside the kiln makes for a sensational sort of indeterminacy as the artwork rises to the challenge of forming and reforming itself.https://artsandculture.google.com/asset/raining-stones-aneta-regel/xAGlSpRuwPcv-g
-
How did you get on?
PIT FIRING WITH TEAK LEAVES
in Educational Approaches and Resources
Posted
I think it very unlikely that an organic plant-based dye would survive the firing process.
Some ideas on colourants in:
A Pit Firing Color Palette
https://ceramicartsnetwork.org/pottery-making-illustrated/pottery-making-illustrated-article/A-Pit-Firing-Color-Palette
Ferric chloride requires the use of adequate safety precautions. Read the literature if you are going to try it. A starter might be
http://jsbarts.blogspot.com/2015/10/use-of-ferric-chloride-safety.html
Some ideas in this thread, perhaps this post is a good place to start