Callie Beller Diesel

I do have a colleague that did some work with bone China, and I think the difference is in bucket rheology. I didn’t have a really extensive conversation with her about it. While it might be technically chemically the same on paper, usually when you have a naturally derived material vs a synthetic one, sometimes there are practical differences. She did say it was a massive PITA to work with. If you’re looking for translucence, you might also consider haloycite based porcelains instead. Polar Ice from Plainsman is one, and I’m sure there are others from US suppliers. You can get dry bags of them if you want to slip cast. They’re still primadonnas, but still more user friendly than bone China. They tend to be comparatively expensive because halloycite kaolins come from Australia mostly, but they’re very beautiful.

I think you’re overthinking it. Especially if you’re doing this as an exercise to be less precious about your work. First, raku is a very immediate way of working, with simple materials that are engineered only to a point. American raku pots don’t meet food safety standards, so you don’t have to be limited by tight chemistry constraints. You work sculpturally, so it’s not a big concern anyways. There are lots of cold processes that can seal a piece so it doesn’t discolour over time. When you see people talk about using floor wax on the end result, it’s not just for shine. Even in HS, we would spray our raku pots with clear varnish to keep them from reoxidizing. (Yes I did raku in high school. It was the 90’s.) What I’ve observed over the years is that as a given artist continues to work with technique, they do it to suit some sort of need they have as an individual. It either satisfies them emotionally somehow, or it provides a specific benefit to the end result. If someone starts with a laborious process and later simplifies it, usually they either got tired of doing the extra steps, they found it didn’t provide enough benefit in the end product, or they found something that worked better. It’s right there in the quote Peter mentioned: lots of other things will work too. If you don’t want to use the Amador, I’d look at the properties that it has that could be germane. Looking at the catalog entry on the website, Amador is a cone 10 clay that is “difficult to crack in firing. Durable and affordable.” So if you’re using it at con 06, it’s going to be refractory as heck, and won’t start to fuse to the pot. It’s a stoneware, which means it will probably have ingredients that give it good green strength that will allow you to handle it a bit roughly. I’m going to guess from my VERY occasional access to some US clays that it maybe isn’t prone to readsorbtion when you dip or pour the waster glaze on it. If you can find a clay body that fits those criteria, that would be a place to start playing. Bonus if the manufacturer sells it in dry bags if you want to use a bunch of it.

Every 18 months or so, I get an order from a local mental health organization that gifts mugs to their crisis line workers and volunteers. I will always do this order, even if it comes at an inconvenient time. It’s a cause close to my heart. I first picked up the gig when I was still transporting work to an art centre to be fired, and saw their request on a bulletin board for someone to design a mug. That was 6-7 years ago.

While my ADHD does appreciate and love a good technical info dump, I think we have to be mindful to tailor our answers to the working level of the person asking the original question. I’m trying these days to tailor my answers so they’re more concise, but provide reference links if anyone wants expanded information. I know I am often guilty of the long letter. I love that we get people from all levels of experience and working styles on the forum, and I think there’s an art to replying to questions so that they meet the OP’s needs and circumstances.

Without knowing the composition of the glaze, you can try altering the glaze with additional ingredients but it’ll be a random guess if it’ll work, and you’ll void any warranties from the manufacturer. And typically, adding feldspar isn’t a remedy for fit issues in any case. If you’re working with a commercial glaze, you’re better off asking your clay supplier what they recommend. They’ll know which clay/glaze combos work the best.

@Ja.Sc. I know you asked Pyewackette, but I also am grossed out when I find hair in my reclaim and have a dog. A second sheet can help keep the hair out, along with covering your reclaim buckets and keeping your hair well tied back so it doesn’t get into the slop bucket. A cover sheet on the reclaim can also help the slab dry more evenly, especially if your humidity is really low. It’ll slow it down a tad, but nothing major.

A grand a month is a good beginning. It’ll increase during the holidays too.

Ah! The flaking kiln wash reminds me. There are non-flaking kiln wash recipes if you’re frustrated with the one you’re using. I use the no-crack kiln wash from this article. If anyone has paywall issues or has used up their 3 articles/month, Sue McLeod has a blog post on kiln wash that mentions the same recipe. She gives some handy application tips (I like the paint roller) and the reasons behind the ingredients. I just use the version with no silica, even in my electric.

It depends on which one. There’s a few possible replacements being tested, and they have different COE’s. Some manufacturers are also opting to eliminate talc from their recipes because it’s become harder to obtain a version that doesn’t occur naturally with asbestos and/or doesn’t fire some shade of amber from iron contamination. Talc is a source of magnesium and silica, and has been most often added to glazes to create mattes in larger amounts, or control crazing in smaller ones. if you add too much, you might get dunting under the right conditions. If the right structural stresses are in play, a change in talc source that your supplier might not have mentioned could have tipped the balance from a combo that was working into one that wasn’t. Talc has also been added to light coloured low and mid fire clay bodies to adjust thermal expansion rates, and some other things. It’s not usually found in darker clays like your stated one, so that wasn’t a likely source in this case. That’s the Cole’s notes version, and if you’d like an expanded rabbit hole with all the delightfully nerdy extra links, Digitalfire does provide! The notes on Tony’s efforts to reformulate a low fire casting body and associated glazes might also be interesting, even if you’re at cone 6. The principles are the same. Another firing mitigation tactic you can try is to place test tiles, other small pieces or even lay down extra kiln posts around the rim of the piece. They’ll create a heat sink so the rim/lip cools at a rate closer to the bottom of the plates. If you’ve been making this design in smaller versions, sometimes the larger one will require extra babying. I can vouch for it working on my pieces, and I notice kiln pack can affect things you wouldn’t think are a big deal. In any case, it’s easy to try.

In everything in clay, there are exceptions that prove the rule. If someone has said “you can’t!” I can guarantee there is someone out there who took that as a dare, and went and did it. But you don’t tell beginners like the OP that it’s common practice, or a good idea to do without a lot of caveats. It’s important to note Steve Branfman isn’t making functional items, whereas the OP was, and that’s a significant distinction. No one is putting flowers in a Steve Branfman vase. I’ve been tailoring my answers to the OP and their reference, or others who might be in a similar boat. It’s my opinion that beginners, like the OP, should not be using glass and ceramic together at all, IF they want pieces to last. Learn about the materials first! There’s a lot. If you want to learn through experimentation, cool! If you like science and chemistry, more power to you! Keep the results for your own reference though, and don’t give them away or sell them. If you have some skill in either ceramics or glass and want to start heading into more advanced territory by combining them, you already know there’s caveats to everything and probably aren’t getting a lot out of this thread. I’d advise against most people using Series 90 or 96 stained glass, or products from hot shop suppliers in ceramic applications, as well as recycled stuff. Bullseye is great stuff for kiln formed glass or copper foil/lead came, but it’s even farther off the COE values of most commercial ceramic products. Plus, a lot of it will alter in colour when fired above kiln-formed glass temperatures, or for too long. Bisque temperatures will kill dichroic effects, as well as many pinks/ purples, and some reds/yellows/oranges. Depends on the colourants used to make it. Glass processes use a wider variety of colourants than ceramicists do, largely due to how we use heat differently.

Some of the underglazes I’ve used did flash onto other pots or the kiln shelves, although they didn’t cause any adhesion. Probably worth a test just to make sure.

A possibility that hasn’t come up yet is if there’s any talc in your glaze recipe, or if you’ve purchased a new batch of materials or pre-mix, whichever you’re using. If your glaze contains talc, it has been subject to a material change in the last few months. The talc that was predominantly used for potters is now unavailable, and manufacturers and suppliers have been scrambling to reformulate around the substitutes that have different COE’s.

When I was learning, we used all the high fire reduction glazes in the wood and soda kilns. If it goes to cone 10, it should work in a wood kiln. Whether it’ll be the same colour or not is a different question The approach for most at the start is to use a celadon or maybe a tenmoku of some kind for a liner glaze. Consider that the flame and placement in the kiln will affect any decoration you do on the outside. You may wind up with dry spots, or you might get a lot of ash deposited that will obliterate any finely detailed decorations. The kiln will be doing a lot of your decorating work for you, so you want to think about how to work with it, rather than against. The edges of flame can leave delicate painterly brushstrokes, or your pot can get the full blast of the harshest part. Depends on what’s around your piece, and where it is. On the outside of pots, tenmokus or shinos can look nice, or even just gestural flashing slip or oxide wash decorations are the most likely to come through looking good against the very earthy palette that wood fire gives you.

Some oxides flux more than others, but usually iron is one you don’t need to add any flux to because it melts at such low temperatures. When you’re doing oxide washes, they’re not something you have to overthink chemistry wise. If the oxide you’re using needs a little extra sticking power, you use whatever you already have on hand. There’s not really specific ratios of what to use. It’s like adding salt to food: how much you use depends on how much you like. Any flux you have will work. Baking soda, frit, borate or borax, soda ash, or as your friend suggested, a little clear glaze that already has flux in it. No need to get anything special for the purpose.

+1 for peroxide. Just throw a shot of it in the bucket, and it’ll take the stink down until more stuff grows.

They don’t work especially without the ash or sodium to react with, no. They’ll just be regular looking slips in an otherwise unaltered reduction firing. They need the uneven application of whatever’s carried by the flame to do the interesting things that they do.

I suspect too that manufacturers tailor their casting bodies so they’re not pyroplastic. I’ve seen it done for things like brick murals.

I use Plainsman M390, and frequently do a white stoneware slip if I want a colourful, translucent glaze to pop. As long as your slip shrinks at the same rate as your clay body, you’re golden. There are lots of white slip recipes out there, and using a white slip over a terra cotta clay body to create a decorating background is a very common practice. Joan Bruneau comes to mind very quickly, and so does Ben Carter, who does the Red Clay Rambler podcast if you want to google for some lovely examples. I buy dry bags of M370 casting slip (same as the throwing clay, but without the bentonite) for my white decorating slip. It’s got the same shrinkage rate as the red, and I only have to add water to it. If I want to do textural work, I just mix it thick. If I want to have a clean surface for decorating, I have just brushed it on in the past, but I found I liked the smooth look of poured slip, so I do have a bucket that I’ve added some darvan to. I did find early that I have to carefully watch when I apply my slip, because my clay body is very susceptible to readsorbtion. Your clay may or may not react this way. It’s something to keep in the back of your mind. If it’s something you’re interested in, I can elaborate, but I don’t want this post getting too long if you’re not. I found when I was using coloured underglazes with a clear coat, if I didn’t bisque the ones I was using before applying glaze, the glaze didn’t absorb well over the UG. Even after bisquing, the pigment itself was a little like terra sig. It was really finely packed, and absorbed better, but not as much as the bare clay did. I was using Mayco brand, so other brands may be different. I also use dipping glazes I mix myself, and if you’re using brush on ones, this may be less of an issue for you.

It would also help us narrow things down a bit if you have a particular look you’re trying to get out of your work, if it’s sculptural or functional, what clay you’re planning on using, and a little background on how much experience working in clay you have. We get folks at all levels of skill here, and it helps to tailor our answers to you.

Is the clay body you’re using a porcelain or a stoneware? And is the speckling happening with any other glazes you’re using? Is it a really pronounced speckle, or is it really fine? If you’re using a stoneware, it could be that impurities from the clay are bleeding through with the extra heat. This would be confirmed if the problem is appearing with other glazes. If it’s only happening with this one glaze, and especially if the speckles are really tiny, the culprit might be the mesh size of either the manganese or the iron. If you can’t get a finer mesh size from your supplier, you could try ball milling the glaze.

+1 vote for 4321. It’s easy to work with, user friendly in the bucket, doesn’t run, it’s cheap to make, and if you need to substitute feldspars or different clays it’s a good intro to glaze chemistry software.

As someone who lives farther north, although I’m not super humid: MOST of the time, none of the kiln firing stuff is an issue, but it might happen a couple times a year. It will be a non-issue if your studio is heated. If you have a kiln in an unheated shelter of some kind, a hairdryer or heat gun won’t cut it to warm the thermocouple. You’ll burn it out. You will want to get a small electric space heater, and pop it in the kiln to run for a little bit before you load. Bonus, this will make loading more pleasant! You need the inside of the kiln to be above freezing so your thermocouple can register anything. For the coldest times, Keep the thermal mass of your pots and kiln furniture in mind if you store them outdoors/unheated. If you have an old cone sitter kiln with no electronics, none of that is an issue. You can just turn it on and go, whatever the temperature. Humidity wise. In the beginning, you’ll want to be able to check your pots a few times a day to get the feel of how it’s working. My “humidity” can fall as low as 35% in the winter, although that’s a pretty dry week. Speeding up your drying is not the problem that time of year! Rims and edges will dry out very quickly, and I’ve seen freshly thrown pots go to nearly bone dry in 12 hours or less. If you make a lot of pots, I recommend building some form of damp cabinet, even if it’s just a matter of having lightweight vapour barrier plastic that you can drape over your shelves. If you don’t make too many things, you might be able to get away with clear plastic bins. You don’t need plaster inside if you don’t want, just a reasonable seal on the box. Or if you want to go old school, dry cleaner plastic over your wareboards. A spray bottle, or some damp sponges inside a container or damp cabinet can help slow things down as well. Flip anything that needs trimming as soon as it can support itself: rims will dry a LOT faster than the thick part you left for the foot, and trapping the humidity inside the pot is very effective at keeping things even. You’ll want to cover mugs for an hour or so after attaching handles to let the pieces marry properly. Right now because it’s a La Niña year, I’m getting rain, the air is heavy and it’s weird! 95% humidity is alien to me! If I had to live with this on a more regular basis and had to turn things around faster, I’d get a dehumidifier. While it’s slowing my drying, it’s not currently impeding my production too drastically, although I did add a one hour soak to the start of my bisque to make sure everything was fully dry before climbing above 100*C. If you’re going to be working in an unheated building like a shed, garage or barn, when the weather cools off, it takes longer and longer during the day for the inside to warm back up. It shortens the number of weeks you can work comfortably in your studio. If you want to work year round, you will have to insulate the building and find a way to heat it. The most fuel efficient thing when it gets really cold is to keep a minimally insulated building at a relatively steady temperature, and if you have a thermostat, not move it more than 3*C/6*F up or down if you are adjusting it when you’re not there. Much more than that, and you waste the energy you saved when you rewarm the space. Even though wet pots are more or less okay until the actual freezing point, working in an unheated studio when it’s cold is unpleasant. When I was still working in rental house garages, I found that once the weather dropped below 10*C/50*F overnight, the cold clay would hurt my hands when I was wedging. I’ve heard of some keeping their clay in an old unplugged fridge/freezer/cooler, but I’ve never tried this personally. I highly suggest using hot water for throwing. While I haven’t tried this personally because I found the tip after I got a heated space, others have suggested using a thrift store crock pot in studios without plumbing to heat their throwing water. Something else to watch are your glaze buckets. Some glazes, especially ones that contain lithium, or borocalcium frits (looking at you, Ferro 3134) can precipitate out some solids if they’re stored below I want to say 15*C/59*F. I don’t remember the exact number off the top of my head, and if someone else does, I’d be obliged. The lithium crystals can be incorporated back into the glaze by dissolving them in hot water. The little calcium balls are much more resistant to being added back in. They don’t redissolve, and it’s a right nuisance to grind them down again. You need a mortar and pestle and a lot of frustration to work off! If you only wind up with a few of them, or small ones, it’s not a big deal, although the lithium glazes will have a much lower tolerance for material loss. If your glazes sit for 2 months and you get a lot of them though, it can affect your chemistry. My suggestion is to keep these glazes somewhere at least room temperature, and don’t allow them to freeze. Or, if you mothball your studio for the winter, use up what you have before the cold and mix fresh in the spring. If your glazes do freeze by accident its not the end of the world, although it is a job of work to get them back in working condition. If the buckets freeze solid, they’ll hardpan like nothing else I’ve ever seen. Some will recommend scraping the solids off the bottom of the bucket with a large loop tool, but I favour a commercial sized kitchen whisk. You will be tempted to pull out a drill and a paint mixing bit: don’t. That will compact it harder. It’s slow going, but you can work out the lumps and re-sieve.

If you do them all in a batch, or at least all the ones you currently own, you have a reference for when you’re using them. As you acquire more colours, you can make the testers for them as you go.

Not weird. Happens a lot in warm climates, or anytime stuff gets in your reclaim. If dandelion fluff, or any of the other seasonal stuff gets in and is left undisturbed long enough, it’ll germinate.

+1 for all comments about moppability! Easy cleanup is important. In addition, if you have a separate room as opposed to a corner of an open basement, have a pair of studio shoes that go onto your feet religiously when you enter the room, and come off when you leave it, even to go across the hall for water. This will make sure dust doesn’t get tracked through the rest of your house. If your basement is dark, a coat of white paint is something I’d really recommend. Also, you will never be sad about additional task lighting. Don’t let your reclaim get too far ahead of you. A larger reclaim bin is not the good idea it may seem like on paper. Do small batches more frequently if you can.