Hulk
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Posts posted by Hulk
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LeslieV, Please do post an update when!
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Hi Janet, Welcome to the Forum!
An excerpt from a Forum member post, "Be aware there are not many new glazes in the 3rd book not in the first 2 books."
Perhaps someone can confirm...
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Coating with slip - even a rather thin coat - adds moisture to the ware, as the OP notes.
Adding slip to the inside (a bowl, for instance), when the ware's almost dry enough to trim, I'll slip the inside, then wait for it to dry some/again before trimming.
For the outsides, I'll add the slip right after trimming.Slipping "too early," the ware can sag/slump a bit - too wet!
Slipping "too late" - idk, I believe I've erred to the early side only (so far). I wanted the slip and the ware to have a chance to equalize in terms of moisture, then dry together.Still good to be cautious though!
Test on your least favorite piece that's about the same size, thickness, material, etc. as your target wares? -
Check the reference guide Reference Guide | Mason Color Works
Most of the blues have refs:
1, can be used as a body stain;
3, max 2300°F;
6, with or without zinc- Bill Kielb and Nata Pestune
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The control board may have some adjustments, however, not finding any documentation on that.
Yep, call Speedball! -
Ah!
Could be the second clay on this page:
CERAMIT :: Plastic ceramic masses (clays)
Several of the words match up in the description...
The full string*: PC 02 W2 - 1180 S 0-21180°C is a solid cone 5
Looks like the clay is fully mature at cone 5 to 5.5 - aim for that, especially if the ware is to be at all functional.I've liked working most of the clays I've tried.
Many clays I've liked, there were problems with glaze fit (crazing) and high defect rate (which I attribute to large particles).
I'm using IMCO clays DC 3-5 (white stoneware), Red Velvet Classic and Terry Clay, however, I throw just about everything - the only hand building I do are the actual handles!
I also liked Laguna Clay WC403, a speckled buff, Cone 5All my glazes are glossy, excepting the Variegated Blue (from Bill Van Gilder's book), which varies between low gloss to a true matt, depending**.
Variegated Slate Blue | Glazy
It goes on well (when properly adjusted) and fires well***.I'd like to suggest looking into what students are using at the school's facility - where you can hear what folks have to say about the materials, and, And, see.
Hopefully, you'll get more input from other Forum members.
*Here's the naming convention key:
**on heat work, the cooling rate(s), glaze thickness, the clay, fumes from neighboring wares...
*** on the DC 3-5
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Hi Yasil,
Welcome to the Forum!
While waiting for responses/input/ideas, can you identify the heat range and clays involved?
Typical heats are low fire (up to cone 1 or so), high fire (cone 10 or so) and mid fire (cone 5/6 or so). Which heat range makes a big difference! Glazes for lower ranges may behave very poorly at higher temps, and those for higher temps may not melt well at lower temps
In my cone 5/6 experience, the clay also matters. The types and rates of defect; the fit*, and appearance/color are all influenced by the clay.
Does the school have glaze ingredients and a lab/station for mixing?
*Fit, where extremes crack/ craze at one end, and shiver/flake off at the other.
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Nice work mug!
My Studio is one bay in a three bay garage.
Heating/cooling - an issue, at all?
If so, a mini-split may serve, which would very likely require addition of an electrical circuit.
While at it, place receptacles where they may be needed, at appropriate heights.
Comfortable temps really help.Lighting has been mentioned.
The light from that one window - and the light from the windows in the garage door - is precious! ...and may influence the layout planning.Work surface heights, that's an individual preference; it's important.
Air movement and dust control
Having some movement - doesn't take much - helps wares dry.
On the other hand, moving air can disturb/distribute dust.
Where floor and work surfaces are easy to keep clean, there's less dust.Where's the kiln go?
How 'bout a door out the back to an enclosed patio (enclosed, but with provision to open up for max ventilation when the kiln is running)?
I liked having the kiln in the Studio for loading and unloading, not so much for how much room it took and having to manage the heat and fumes. Space. Heat. Fumes.Is there water just outside the rollup door and/or the person door?
That would serve, however, a plumbed sink might be nice; the drain could/should go outside, or through a "French drain" or a clay trap...Surround sound.
Great chairs that suit the workstation and the worker(s).
I'd think about getting a start on't, but not to lock in the layout, design decisions, workflow, colors, finishes, heights, which station gets which view, and, heh, everything.
- Min and Kelly in AK
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Hi Laurel,
Welcome to the Forum!
I'll move your post to "Community Marketplace – Buy/Sell/Trade/Free" subforum.You might include an image, if possible?
Here are a few archived threads featuring Estrin wheels:
Estrin Potters Wheel - Studio Operations and Making Work - Ceramic Arts Daily Community
Estrin Wheel - Equipment Use and Repair - Ceramic Arts Daily Community -
Hi Lana9, Welcome to the Forum!
Kiln shelves are "...support element...flat, rigid surface which carries the ware during firing, sintering or heat treatment."
Here is Mark C. with his car kiln*, where thirteen levels have been glaze fired.
The large flat horizontals are kiln shelves; the vertical supports between levels are posts.
Shelves and posts are "kiln furniture" - there are some other types of supports ...shelves and posts may be the most common.
Note that Mark's shelves are remarkably thin!
The thin (and comparatively light!) type are more expensive, however, they last well, leave more room for wares, and allow for a much lower total load (in mass).This article explores different types of shelving:
The 5 Types of Kiln Shelves You Need to Know About - Blog (baileypottery.com)*From a Ceramic Monthly magazine article, "Lessons Learned Over Time"
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Clay Art Center is listed as an IMCO dealer.
...however, Clay Art Center's website does not list any IMCO clays.
My bad.
I like their DC 3-5, Red Velvet Classic, and Terry clays (whitish, red, light tan - all 5/6). -
I also like the write up in Susan Peterson's book, The Craft and Art of Clay
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Hi Kinosfronimos, Welcome to the Forum!
Good question.
I'd like to suggest looking into potential colorants, but only using materials that are safe (at least low risk) for the potter and the ceramic ware user.Tony Hansen's page on "Common Ceramic Oxides" is exhaustive, when paired with "Uncommon Ceramic Oxides" (linked on the same page):
CaO (Calcium Oxide, Calcia) (digitalfire.com)...that's all oxides; some are used as colorants.
See also:
Colorant (digitalfire.com)
Please see paragraph beginning "Metal oxides (e.g. iron oxide, cobalt oxide, chrome oxide) can be completely safe or have considerable toxicity." (emphasis added)Really bright and vibrant colors that are also safe (digitalfire.com)
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Nice shape, burly foot!
I'm curious how thick is the portion that's cracked, after trimming is complete.
The foot ring appears to taper down to the portion that touches the table - thicker where it intersects with the cracked part, the web across the bottom.
Is the cracked part appreciably thinner than that surrounding ring? If so, would it not dry, shrink, and be held taught by the still damp ring around it?Yesterday I trimmed and handled two mugs.
At trimming, the bases are a bit damper than the upper portion. When set aside, there's a millimeter or so clearance between the middle of the base and where it would touch a table.
This morning, that arc has flattened; now there's two+ millimeters of clearance. -
Very fortunate to have only two or three "s cracks" over six plus years; on the other hand, I haven't learned much (by direct experience) about them...
The clay in contact with the bat (or wheel head) can't move about as much, and hence isn't "compressed" nearly as well, I believe.
I cut feet in just about everything, so the "uncompressed" bit is eliminated.In my process, the upper portion of the form is dryer/firmer than the bottom portion when it's time to trim; the bottom portion is last to dry.
The section within the foot ring, if it is able to dry out - and hence, shrink - well ahead of the surrounding clay, well, something has to give!
Where the bottom isn't appreciably thinner than the surrounding clay, very likely that helps...
The arc* in that section - if any - can flatten as it dries; that seems to help.
Mark, does your thumping stretch the bottom, hence providing some slack for drying?I'm burnishing that same section (within the foot ring) immediately after trimming; maaaybe that helps, a little.
*I'm trying for the base to have a slight arc.
On the final pass when the wares are thrown, I'm expecting the base to be lowest in the middle, by a smidge.
Then, when trimming, the outside follows the inside.
As the ware dries, the base flattens, a lil' bit... -
Glazes that see regular use*, six.
Liner glaze, translucent white
Clear Blue, Variegated Blue, Teal Blue,
Rutile Green,
Red (it's somewhat transparent)I also use several underglaze colors, all Speedball.
I'd like some yellow, both underglaze and glaze; the glaze, likely via a yellow stain.
*not counting remnants from tests and such
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Yep, allow to settle and take off the clear portion, then, without there's "enough" H202 to fully clear the stink, it will just be not as bad for a while, then recover its full form after not very long.
The other point, the smell recedes and clears as the clay reaches (dries out) sticky to "almost there" status.
That's been my experience.I was curious how much help a small squirt would be - would it take the edge off? For a few days.
It's getting to be Summer 'roun' here. The floor mop and throwing water buckets get yucky fast! -
I gave the red clay slop bucket* a squirt of hydrogen peroxide a few days ago. The clear(ish) water portion, much improved for a few days, however, the clay portion about the same stinky, and the clear portion, well, I skim it off periodically... ...mixing the peroxide about would likely help - I'd tried that, early on, but have just let it stink since, for once the reclaim process is well along - to the point where almost ready to ladle out on plaster - then stink retreats.
*Most of the reclaim gets thoroughly dried out. The throwing bucket slop goes to a settling bucket, where it will eventually dry out if left undisturbed long enough and become a dense disc.
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Is the kiln fitted with the Quad elements?
The bit of element in the pic looks really good.
Any chance one of the elements isn't heating well?
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Given the cup runs true when mounted up to the shaft, making or adapting something to attach as a wheel head might be straightforward?
Just lookin' at it, I'm imagining a wheel head that bolts up to the holes in the cup... -
Hi Delis,
Welcome to the Forum!
Looks like you're well over cone 6 there.
Half an hour of soak at peak, that would add a lot of heat work!
If you're thinking a soak is required*, try "drop and soak" - where you drop 100°F (~56°C) then hold.How long your kiln takes to reach peak temperature - the last 100°C or so - that's key, as Bill points out.
If the kiln is struggling to reach peak, you'll adjust the target/final temperature down...
If the kiln can reach peak temp easily and quickly, likely you're governing that final rate via the last ramp's programmed rate.
*Drop-and-Soak Firing (digitalfire.com)
I'm doing this... -
Typically used as part of glaze formulations, it is a primary ingredient!
For low and mid fire glazes especially, the finer (smaller particle) 325 mesh is recommended over the 200*; see "The difference between Silica 90 and Silica 45" about third of the way down the page, here: Silica (digitalfire.com)
Silica can be an important ingredient in clays as well.
Dust control can be - it is - important when working with Silica (and other fine powdered materials).
*I'd mistakenly bought the 200 mesh, which may have been a factor in my struggles to eliminate crazing in my liner glaze.
Between lowering the COE (via formulation change; thanks to this Forum for support and specific information and suggestions), adding a smidge of lithium (via Petalite), and an extended hold (100°F below target/peak temperature - "drop and hold"), the crazing seems to be well under control.
Still, I'm looking forward to getting a sack of the 325 mesh! -
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Hi yoony22, Welcome to the Forum!
Good question.
This Tony Hansen article references a lead test kit: Is Mexican Terra-cotta pottery lead-glazed? Yes. Does it leach? Yes. (digitalfire.com)
...try "pottery lead test kit" as a browser (and/or A**zon) search string - lots of results!What temperature(s) are they firing to?
My guess, low fire would be much more suspect than mid fire.Are they mixing their glazes? If so, are the materials visible/available?
Is the glaze mixing area anywhere near the workspace?
Are the kilns nearby? Where do the kiln fumes go?
Could Someone Give me Advice on Glazing Techniques for a Smooth, Even Finish?
in Clay and Glaze Chemistry
Posted · Edited by Hulk
added
For insides, I'm pouring in and pouring out.
For outsides, I'm dipping - mostly upside down - excepting for wares too large for my glaze buckets, then I'll pour over.
The pour overs don't come out evenly, hence, I'm embracing the look in those cases...
I'm brushing underglazes and using brushes to touch up and for highlights, etc.
Several factors come to mind:
A-1 factor (for me) is adjusting the Specific Gravity (aka SG, how wet) and thixotropy of the glaze; see Tony Hansen's articles and video clip on the subject*.
SG, when lower (I'm working between 1.39 to 1.47, depending on the glaze), one must hold the dip longer to get the desired thickness - there's more time to complete the moves. On the other hand, there's more water absorbed into the clay, and hence, the drying takes longer.
I don't mind longer drying time in exchange for not having to Hurry Up when applying glaze.
Thixotropy, critical notion, where the glaze behaves as a liquid when it is moving, but gels when not moving.
With a good adjustment, the glaze doesn't run, sheet, drip nearly as much. At all.
Measure SG, hence it is a constant and repeatable factor (write them down).
Measure thixotropy as well, but how?
I stir at a repeatable speed, then count the revolutions to full stop, like Tony's doing in his video clip.
Note the "bounce back" when the glaze comes to a stop, all together.
This is key!
A-2, technique and repetition!
Practice! Here's where choosing a larger kiln (7 cubic feet is bigger than I really need, mostly) helps; there's more pots to work on!
Pour in - enough glaze so there's enough to get around the rim on the pour out without struggling.
Pour out - aim for an even stream - just fast enough for no dribbles - where the end of the pour just meets up with the beginning - voila! An even coating!
Dip - push the ware down, withdraw slow and even; speed is important - too fast, and even a well-adjusted glaze may slump a bit, and too slow, well, the glaze layer will be too thick.
Run the last drops around and around the rim before righting the ware; keep a damp finger handy, wait, wait for the glaze to just loose its sheen before smoothing any drops, there.
Other:
Mix it! Stir that glaze! As necessary, before each action; some glazes, only takes a few minutes for the surface to get watery - stir it. Stir it.
Find the hot wax, wax resist, tape, rubber band, ?? techniques for borders/edges that works for you.
Keep a small sponge handy for picking up drops off waxed portions and et cetera, and a bucket with water and a large sponge for cleanups.
Inspect carefully after the glaze if fully dry - touch up any pinholes, crawls.
Helpful tools: kitchen whisks for stirring; a long scraper for stirring the bottom edges of those buckets, where the whisk can't reach; turkey baster, ear syringe for squirting glaze and sucking it up as well; kitchen ladles for pouring - ladle that works for you, no dripping; a funnel to get glaze in narrow necked ware - where the turkey baster would work, but a funnel is easier.
That's more than enough for now?
If somewhat else comes to mind, I'll add it!
*How to Gel a Ceramic Glaze (youtube.com)
Thixotropy (digitalfire.com)
Added:
Check thickness of the dried glaze layer - scratch away a small bit to check, then patch it back.
or
Incorporate small accent(s) - apply a square/diamond/circle/?? bit of tape (masking tape); when the glaze is dry, wax around the tape; when the wax is dry, pull the tape, check the glaze thickness; fill the spot with a complimentary/contrasting color.
I'll use the "tape trick" when applying glaze via spray.