Callie Beller Diesel

Are you sure that’s iron oxide? There’s lots of other possible solubles that turn brown.

While I add dry ingredients directly to my old batch at my personal studio all the time with no ill effects, if you’re in a teaching studio, you might want to mix the new batch separate and test it to verify everything went as expected before adding it to the old batch. And depending on how well the studio members/students are mixing the batches, you might want to let it run out as far as possible before adding new. If incomplete mixing is a habit, it can mess with the glaze.

This one from my students. If you manage to wear the skin off your pinky, vet wrap is a good way to protect it.

If you can’t get proper pottery plaster for a reclaim slab, you can lay an old sheet over wire racking and lay thick slurry out on that to dry.

We love updates! May the moss growing go well.

I used paper clay for a couple of years. It lives up to all that hype! It’s much more forgiving about when you attach pieces, so if you’ve got time constraints, it’s a great material. The 2 main things you want to watch are the stink from cellulose breakdown, and to be mindful that then end piece will be somewhat more friable than the same piece made out of regular clay would be. How much more friable will depend on how much pulp you add. The rot can be managed in a few ways, the easiest being to only mix up what you’ll use in a short time frame. The next easiest is to prepare a larger batch, and dry it out in really thin sheets that can be stored and rehydrated as needed.

If the mixture is homogenous, the shrinkage rates should wind up somewhere in between the 2 different points. You’re making a whole new clay body.

In all the years I had to transport work for firing, I found the best fix was to have small sealable sandwich bags of glazes to do touchups when you got there.

@semidoomed if the glazes are only being fired to cone 04 and cooled in a normal firing, the clay body won’t matter a great deal. If they do want to pull the pieces out of the kiln while hot, it’s a good idea to wedge in a bunch of grog if there isn’t any already to help ease some of the thermal shock.

Usually the good liquid wax emulsions do tend to be more expensive than the ones that tend to pill. The paraffin will be less expensive, and I second Hulk’s idea about a crock pot or an old rice cooker used to keep it warm.

Your kiln firing cycle sounds good, although the overnight hold may be excessive. For a 1 cm ( about 3/8” for the Imperial users) thick piece that’s bone dry, I don’t know that more than 3-4 hours is necessary, even allowing for a more humid climate than mine. We use a 4 hour hold at the teaching studio I’m at, and most learners make some pretty chunky pieces when just starting out. The end durability of the piece in your garden will be dictated more by your clay body’s fired properties and how they interact with your climate. Freeze/thaw cycles will be important, and I’d follow whatever recommendations they have in your area for overwintering terra cotta plant pots. Potterycraft doesn’t appear to offer porosity testing specs on their, but they do say it’s reasonably groggy (6/10). With a 30 minute soak at the end of your firing, I would expect your end firing temp to hit 1200, or a good cone 5-5.5. A bit under the cone 6 end point on this clay, so I would expect some porosity in the end piece. Enough to absorb some water over time, especially somewhere damp enough to grow moss.

As a regular red clay user, darker clays are going to have a different effect on glazes than lighter coloured ones do. Even leaving out the possibility of oxide interactions, the dark background behind any translucent/transparent glaze is going to reflect light differently than a lighter coloured background will. If you take this effect into account and work with it rather than against, you can get much more satisfying results out of your glazes, whether they’re commercial or homebrew. Darker clay bodies DO work well with commercial glazes, they just don’t look the same as the sample they only show on white clay, and that’s frustrating. I have no idea why they only show samples on white clay, because there’s a huge range of clay colours out there, but here we are. As a general rule, yes, if you’re using brush on commercial glazes, you will have to add more layers over a darker clay for best results. You’ll need the extra pigmentation to overcome that aforementioned dark background. Even on light coloured clays, a too-thin glaze layer is gonna go that yucky green or brown. With darker clays, doubly so. You may find that variegated glazes, or glazes with titanium or rutile will actually look much better on red/dark clays than they do on lighter lay bodies. The extra iron kicks those rutile blues into overdrive, and it’s really nice. If you want a result that’s closer to the samples, you probably also want to choose more opaque looking glazes, or even add a white slip over your red clay to pop certain colours. Or even use it as a way of getting 2 different effects on a piece with only one glaze. You are not likely to get light or pastel colours to come out true on red clay, unless they’re highly pigmented or contain a lot of opacifiers. Even then, they’ll have a more tonal cast to them.

@Crooked Lawyer Potteris your kiln vented? I’m not sure if it’s the atmosphere or the temperature that’s different, but if you’ve ever had a chance to look inside a pot that’s at temperature, usually either a raku or wood fire where you could see inside the kiln, you can see that there is indeed a difference in the glow on the inside bowls and cups, and it moves with the kiln’s atmosphere. (My optometrist would like a word with 20 yo me.) If that fluctuation is from gasses from the kiln atmosphere, or even from materials decomposing and being contained in more upright forms, venting might take care of it. I notice that your bisque temp is quite low as well. Have you tried going up to cone 06 for the additional burn off?

50 years ago, the standard was also cone 10 reduction, and I think cone 6 was filed under “interesting but impractical.” So the extra heat work took care of the difference that the silica mesh size would have made. 200 mesh sil-co-sil was all I could get back in the 90’s, so I used it. And I was firing at cone 10 at the time, and it was fine. When I made the switch to cone 6, I came across much of the same info you’ve already listed, and the 350 mesh was more available. I was less concerned with crazing at the time, but I can say that the mesh size makes a difference in glaze clarity at cone 6.

If you’re making functional ware, spray paint isn’t going to be a good route. Sculptural stuff? Cold finishes all the way. It opens up sooooo many cool possibilities.

Mostly throwing large amounts of items on a slow wheel with soft clay is an exercise in economy of motion. In the absence of knowing exactly what you’re doing/not doing, it’s hard to troubleshoot exactly. A good resource to check out might be YouTube though, because sometimes a video can reveal a lot in a short amount of time. If you find it difficult to watch a video tutorial, something that can help is adjusting the playback speed. But if you need text versions, I’ll tag @PeterH, as he’s got a gift for tracking down all kinds of good articles. I’m curious as to why you’d want to use a kick wheel if you’re going in to production pottery though. Kick wheels tend to be harder on the body than electric ones, and that’s an important consideration when you’re looking at a job that can have a high propensity for repetitive motion injuries. Production pottery of any kind is about economy of motion and making things efficiently, so that you can make a lot. Any choice made about how you work that isn’t about efficiency has to have a compelling reason to be included in your process. If you’re using a particular technique that takes more time, you have to find ways of offsetting that elsewhere in the process. Or the results have to be able to provide enough value in the finished work to be worth the effort.

@tyler it could be a good idea to check with your local clay supplier if anyone who can do that for you. Every clay person I know likes to talk about what they like (clay) to anyone who will hold still long enough to listen to them. They’ll know someone who knows someone.

Usually I work things pretty close together, so I don’t need a lot of “long term” (more than a week) storage these days. Mostly I use a double layer of plastic to cover things, but I did get a large under-bed plastic tote for handles that I use in a similar manner to what you describe @Pres. I have to ask though: why the board or plate over the sponge? I’m picturing a small throwing sponge or similar, as that’s what I use.

I found a reference on the Laguna website that said they acquired the Westwood Ceramic Supply company. I’d suggest reaching out to them. I didn’t find any glazes in their current catalog with a WR number, but they may have older records.

Your new teapot is unlikely to cause you any harm, short of breaking it and cutting yourself on a shard accidentally. It doesn’t have any warnings about lead or cadmium, nor do I see any colours or textures in that line of work that would lead me to suspect any use of those materials. If you’re super nervous about anything and want some reassurance, you can get lead test kits for pottery on the ‘zon, but I’d be surprised if this item came back positive. In the product description from your link, where it says Material Icon, there’s a number of little care instruction and definition buttons. When you click on “Iron in Powder” (likely a translation vagary) it points out that there may be some dark specks that appear in the final piece from iron impurities in the clay. There’s going to be considerably less iron that could possibly come out of this teapot than, say, a cast iron frying pan. Glaze doesn’t work the way you’re describing, no. Whoever gave you that description may have been thinking of earthenware that was painted with some kind of lead bearing decorative slip or underglaze, but even that has some dubious underlying assumptions. First, not all pottery is made in the same way. Without getting overly technical, different kinds of clay that people use in different parts of the world will have different levels of porosity, firing temperatures, and a bunch of other stuff. So items made in Japan won’t use the same techniques or materials that get used in, Mexico, or the US, or even Canada. And studio pottery will not be made with the same materials/techniques as industrially produced items. But in general, glaze is used on a clay body to make it stronger, and to make it more waterproof and easier to clean than just the clay surface would be alone. Also, it makes it pretty! ****IF**** a piece of pottery were to contain lead or cadmium, it won’t be in the clay body. Those metals will typically be present either in an underglaze decoration (they make pretty reds, yellows, oranges and some greens), in some forms of china paint decoration, or in the glaze itself. It’s important to note that a lead free clear over a lead or cadmium bearing underglaze **might** not block all lead bleed through should those materials be present. It’s also important to remember that not all yellow/red/orange/green underglazes or glazes will have any of those things in them. There’s lots of ways to get those colours that don’t involve those metals, and are safe for daily use.

I’ve always lived in hard water areas (my city’s website lists PPM in the 180’s for most of the year), and my fingers have likewise always wrinkled with extended exposure to water.

It looks like it’s a mineral of some kind (likely iron) bleeding through the glaze from the clay body. It’s quite common in stoneware clay of any kind. Nothing out of the ordinary at all.

The studio I work at does something similar, and we wind up using hair dryers to set up the surface of the piece enough to take a coat of underglaze that isn’t streaky.

I try to keep to five glazes in my own practice. In recent years, it’s been 2 base glazes with different colourants in them, and that will get you a lot of possible variation to work with. If you try to have too many glazes, it gets overwhelming fast. 10-12 glazes is a roster you’d expect to see in a group studio or some other teaching environment, and it gets complicated to find that many that will work together well, without any of them being a PITA.

Trying it once isn’t definitive. Don’t give up quite yet. Firing it while still wet won’t get rid of the shrinkage, it’ll just all happen when it’s on the kiln shelf if you do that. If shrinking from wet to dry is caused by water evaporating, you have to find a way for there to be as little water as possible. So mix the slip as thick as you can and use darvan to create flow if needed, use calcined clay materials in your ingredients, and you may even have to go as far as adding some gum or other binder to the mix. It’s going to take a lot of experimentation and playing with materials to figure some things out in this area.