Clay particle orientation and joining slabs

[andrewiles]

So Andrew you are not using the plaster in the bottom of those storage containers? You're having good luck without that? Nice rectangle!

No, I don't have any plaster handy. But also, I think the wet box is more for keeping the clay wet indefinitely rather than drying slowly. My approach has been to roll out the bottom, feet and extrude the sides on day 1, then dry under cover lightly. On day 2 build the pot and dry under cover lightly. On day 3 do some touchup and then start slow drying process in the storage box. Only done this twice so far though, so we'll see. I haven't bisqued anything yet after doing this.

It seems to be working so far. I'm taking it very slow, so if the pots stay uniform I'll speed it up a bit more next time.

 

[ABCarve]

Yeah, I'm, finding that when people say dry slowly and evenly, they mean it. I had a pot at the local studio under a plastic sheet and against a wall. It dried out in about a week but had a warped side from where it had dried much faster away from the wall.

Now I'm drying my pots in some storage containers I had laying around. I open the lid for a bit each day. Once the lids go back on the humidity jumps back to 99% within a few minutes -- amazing how quickly the clay releases water.
View attachment 420120

Grog grog grog. How much grog/filler is in your mix? If it’s a clay body is for throwing it’s probably not what you’re looking for. Try a sculpture clay.

 

[sorce]

make a small pot as an experiemnt

Be aware that a small pot is, due to the proportionality of shrink, a small experiment.

Larger gives more to read.

You can just roll and extrude long pieces and measure the shrink.

Sorce

 

[andrewiles]

Grog grog grog. How much grog/filler is in your mix? If it’s a clay body is for throwing it’s probably not what you’re looking for. Try a sculpture clay.

Unless I order something online and pay who knows how much in shipping I'm looking at limited options here. I'm trying this: https://seattlepotterysupply.com/co...nge-cone-6-vashon-buff?variant=39390198890635 right now but they don't say how much grog is present. Sent them an email just now. It still shrinks 12% when fired.

I've been mostly using this: https://seattlepotterysupply.com/collections/mid-range-clay-4-6/products/sp698-eclipse-pottery-clay which actually shrinks less even though the grog is at <5%.

Dunno, can you recomment an online source of a good high grog clay that I can try? I'd be willing to order a 50lb carton once and pay for shipping, just to compare the results with what I have locally.

 

[ABCarve]

547 Red Sculpture

C/2-6 Contains fine and medium grog. Good for tile and sculpture. Low absorption at cone 4-6. Cone 6 Average Shrinkage 10.0% Absorption 0.25% Product Number: 10547

standardceramic.com

This is ^6 and .25%.

 

[ABCarve]

Putting a lip on the pot, either internal or external will help. I’ll slightly bow the walls outward to mediate as well.

 

[andrewiles]

547 Red Sculpture

C/2-6 Contains fine and medium grog. Good for tile and sculpture. Low absorption at cone 4-6. Cone 6 Average Shrinkage 10.0% Absorption 0.25% Product Number: 10547

standardceramic.com

This is ^6 and .25%.

Thanks. I'll give this or something like it a try.

 

[Pyewacket]

I'm schlepping hardiebacker ware boards to the studio now. I've had a bowl blow out the bottom (during glaze firing) from uneven drying - there's been a changing of the guard there as of a few months ago and a lot of stuff grew legs and walked, we were having to dry stuff ON the plastic bats for awhile. No ware boards.

It is very dry here and the other day several of my newly thrown items turned up half dried out before I realized a door was open ... So those got squashed. I'm hoping the superior wicking ability of the hardiebacker will help to even out some of the drying issues (by accelerating drying of the bottom to catch up to the rims). It's worked for me in the past.

That, and paying more attention to whether fans are on or a door is open when I've got stuff out.

I like throwing a lot more than coil and slab so I've been seeking less groggy alternatives. I have a few stoneware options available semi-locally (6 to 7 hours drive, I live in a clay desert) in the 1% absorption range.

 

[August44]

Are you thinking "HARDY BACKER" HAS MORE ABSORBSION THAN REGULAR DRYWALL? You have to watch heavier pieces and rotate and flip them for even drying. I also keep plastic tight on then initially, so they start out with even moisture. Let them dry slowly. Quick dry gives you what you got.

Put where you are from under your logo

 

[mwar15]

I’ll put the pot on drywall that is covered with a plastic bag,put the clay on the plastic bag and then put that inside another plastic bag. It is to get everything equalized moisture wise. It essentially is the same as your tote

 

[Pyewacket]

To each their own. I personally won't use wall board. But lots of people do (obviously).

I'm not trying to speed dry, just want the bottoms to dry more in line with the rims. I wrap in plastic at the studio. But when all you have for ware boards are glazed tiles and plastic bats, the rims are still gonna dry faster than the bases. At home (when I get set up, I'm still getting situated after a move) I use damp/dry boxes (whichever I need).

I've been using hardiebacker exclusively in preference to plaster for 10 or 12 years. Works a lot better, makes a lot less mess. And, its portable, which plaster slabs are not really. If it gets waterlogged - which I have to say has never happened that I can recall - it'll dry out way faster than a waterlogged plaster slab. Which I HAVE seen happen (with plaster) when you are trying to dry out your reclaim. Not the greatest for spiral or ram's head wedging or kneading because it is VERY efficient at drying, but who does that anyway (JK!). I've been stack 'n slam for 50 years. Takes way less time and way less contact. Spritz the hardiebacker with plain water so it doesn't automatically suck all the water out right away LOL!.

But I'm getting a Peter Pugger here in a few months anyway, so that puts paid to the reclaim. AND the wedging.

I've got some cut now to use as throwing bats, just have to measure and drill the bat pin holes. The only thing better for popping your piece off a bat without having to wire is Hydrostone (which yes, is TECHNICALLY a type of plaster but its way better than the ordinary stuff, especially the Plaster of Paris people still insist on using instead of the pottery-specific types). I may skip that - turns out I can get some Hydrostone bats not too expensively "locally" when I make my clay-and-plant-buying trip in a few weeks.

 

[August44]

To each their own. I personally won't use wall board. But lots of people do (obviously).

I'm not trying to speed dry, just want the bottoms to dry more in line with the rims. I wrap in plastic at the studio. But when all you have for ware boards are glazed tiles and plastic bats, the rims are still gonna dry faster than the bases. At home (when I get set up, I'm still getting situated after a move) I use damp/dry boxes (whichever I need).

I've been using hardiebacker exclusively in preference to plaster for 10 or 12 years. Works a lot better, makes a lot less mess. And, its portable, which plaster slabs are not really. If it gets waterlogged - which I have to say has never happened that I can recall - it'll dry out way faster than a waterlogged plaster slab. Which I HAVE seen happen (with plaster) when you are trying to dry out your reclaim. Not the greatest for spiral or ram's head wedging or kneading because it is VERY efficient at drying, but who does that anyway (JK!). I've been stack 'n slam for 50 years. Takes way less time and way less contact. Spritz the hardiebacker with plain water so it doesn't automatically suck all the water out right away LOL!.

But I'm getting a Peter Pugger here in a few months anyway, so that puts paid to the reclaim. AND the wedging.

I've got some cut now to use as throwing bats, just have to measure and drill the bat pin holes. The only thing better for popping your piece off a bat without having to wire is Hydrostone (which yes, is TECHNICALLY a type of plaster but its way better than the ordinary stuff, especially the Plaster of Paris people still insist on using instead of the pottery-specific types). I may skip that - turns out I can get some Hydrostone bats not too expensively "locally" when I make my clay-and-plant-buying trip in a few weeks.

You work clay way different than I do!

 

[Pyewacket]

You work clay way different than I do!

In what way? Tools are not the same as working the clay ... Just curious.

 

[penumbra]

You work clay way different than I do!

We all do it a bit differently, yet we all get it done. Results do vary.

Thanks. I'll give this or something like it a try.

This one, #547, is the one I use for most of my Stone Age pots. Very groggy and breaks with edges like a rock.

 

[andrewiles]

We all do it a bit differently, yet we all get it done. Results do vary.


This one, #547, is the one I use for most of my Stone Age pots. Very groggy and breaks with edges like a rock.

Yeah, grog makes a huge difference. I picked up some 420 and while I haven't figured out how to keep a smooth finish, it maintains shape. Probably try 547 next.

Still quite straight, after bisque:


My first rectangular pot using throwing clay turned into an abstract wave by the time it was done in the kiln

 

[sorce]

. I picked up some 420

I would test a quick piece or 2 before making too many pots with it. There was a calcium problem with the grog that may not have been fixed. Makes for lime pops which, if you're like this woman who was making busts and glaze firing them once, can ruin a brand new kiln!

Reckon it may be best to make unglazed pipes!

Sorce

 

[andrewiles]

Final pot for now. Probably pick up again in the fall. This one is 21 inches by 12 inches. Biggest I can do in the studio's kiln.



I've made 9 pots so far and most ended up warped or saggy in the end. This is the best so far, with straight lines and no wobble. Glaze is a bit wonky but that wasn't the focus up to now.

Things I've observed to get to this point:

• Grog is good. Lots of it. I can't keep straight lines unless it's a sculpture or tile clay. Other factors like clay particle orientation seem minor in comparison.
• Clay extruders save a lot of time for the sides. Bonus for having a 3d printer to create templates.
• Foam molds really help, even with drier clay. I feel like this removed a lot of the "years of practice" requirement to get clean sides and corners.
• Slow drying is good. I found drying in a big storage bin helped, since I could repeatedly close the lid to let humidity jump 100%, equalizing the moisture content across the piece.
• Midfire center support helps. I found that on pots this big the center sags without center support during the final fire. I used a thin piece of clay matching the thickness of the feet.
• Glazing is some dark art I don't understand yet. Need to work on that.
• This is really a detail-oriented art. To get clean lines I had to spend time. On molds, on ribs, on touch up, on drying.

I think to proceed further, esp. with glazes, I'd probably need to buy a kiln. Not sure yet if I want to invest in that. Since I want to make large forest pots I'd need a large kiln. So, ahem, $$.

Appreciate all the feedback from folks over the past few months. It's been really helpful.

 

[JeffS73]

Final pot for now. Probably pick up again in the fall. This one is 21 inches by 12 inches. Biggest I can do in the studio's kiln.

View attachment 434425View attachment 434426View attachment 434428

I've made 9 pots so far and most ended up warped or saggy in the end. This is the best so far, with straight lines and no wobble. Glaze is a bit wonky but that wasn't the focus up to now.

Things I've observed to get to this point:

• Grog is good. Lots of it. I can't keep straight lines unless it's a sculpture or tile clay. Other factors like clay particle orientation seem minor in comparison.
• Clay extruders save a lot of time for the sides. Bonus for having a 3d printer to create templates.
• Foam molds really help, even with drier clay. I feel like this removed a lot of the "years of practice" requirement to get clean sides and corners.
• Slow drying is good. I found drying in a big storage bin helped, since I could repeatedly close the lid to let humidity jump 100%, equalizing the moisture content across the piece.
• Midfire center support helps. I found that on pots this big the center sags without center support during the final fire. I used a thin piece of clay matching the thickness of the feet.
• Glazing is some dark art I don't understand yet. Need to work on that.
• This is really a detail-oriented art. To get clean lines I had to spend time. On molds, on ribs, on touch up, on drying.

I think to proceed further, esp. with glazes, I'd probably need to buy a kiln. Not sure yet if I want to invest in that. Since I want to make large forest pots I'd need a large kiln. So, ahem, $$.

Appreciate all the feedback from folks over the past few months. It's been really helpful.

Nice pot Andrew, it's been really informative following your progress in this thread, thanks for posting.

 

[sorce]

I think to proceed further, esp. with glazes,

You can cut through a lot of confusing BS about dipping, brushing, coats, and how each differently relates to each of specific gravity, type of brush, length of dip and porosity of clay being dipped, which also then has to be bisqued perfectly to a specific cone, rinsed or not, blah blah blah....

And just focus on actual thickness of glaze by just looking at it or with a scratch in an inconspicuous area which can then be thumbed more inconspicuous.
And how 2 glazes react when layered, mixed, or otherwise combined.

Of course, because the most important thing is to fire slower and longer than most community kilns care to or can fire, pinholing, crawling, and every other of the numerous "problems" no one can ever figure out with glazes may plague the process.
As soon as you get up over 16 hours, the only problem results from 2 glazes that just don't play well together. One easily solvable problem with just good notes.

Every ingredient in a glaze melts at a different point and over a different length of time, Phil goes over this in an episode of The Potter's Round Table.
It's important to understand how cones work to measure temperature and time to understand how this makes sense as it relates to glaze chemistry functioning correctly during fire.

If these lines represent materials and their melting ranges during a fire.....


Observe how many possible new interactions we create with fluxes and non fluxes during a longer firing.


By drawing out the firing, we draw out the length of each materials period of activity and interaction. This is the problem preventer.

With short firings, we allow for some materials to go mostly through their process without possible interactions of others. With no stiffener available in the matrix, a flux may be too strong. With no flux available in the matrix, a stiffener may go dry.

You shall have a kiln and with patience and determination have it for FREE!

Get alerts on OfferUp and Craiglist for kilns.

Me and my guy are fittin' to build him a minigama out of halves(ripped lengthwise) of electric kilns over a dug pit floor lined with firebrick.
Making plans to use an old kiln as a bourrybox to fire another larger one with wood.

All this stuff has been "acquired", not purchased.

You Can do it Cost free, just get and remain plugged!

I reckon there are no less than 2 schools in each state with equipment they would give away to the first person willing to move it. Like entire Gas Systems and such. Mad electric bodies.

Will It!

I think it was our boy Nick Lenz with me the other day, heels out the dumpster that brought me to this seedling starting mat I found the other day.
Now I can get my Okra started.....

Okra as in...

Ok Ra....let's do this shit!

Will It! I willed myself a deck full of lumber for my raised beds, 2 rain barrels, some old fence to pretty them up, some clover from a bag of excellent compost materials, a lawnmower, almost everything I need to do everything I need to do.
I reckon it's cuz I vowed to share excess, the world wants you to have what you want if you want it to appropriate levels. My neighbor enjoyed one of eight bottles of wine I procured the other day. Me, I just been drunk!

Sorce

 

[andrewiles]

Yeah, and I could go with a small old kiln to start, to test clays and glazes. And only find something bigger once I was confident I had the fundamentals down.

Creating and mixing glazes does seem like a lot of fun. Just need control over the kiln.