Callie Beller Diesel
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Posts posted by Callie Beller Diesel
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It sounds like you’re using commercial dry mix, correct?
The only thing to be mindful about storing glazes outdoors in the heat is evaporation. Check your consistency and maybe measure your SG before each glazing session to make sure the consistency is where you want it. This should be done anyways, but life does happen.
More issues happen with cold. I had an unheated garage studio for a long time. Freezing glazes isn’t the end of the world, but it does make dipping glazes hard pan. You can rescue them, just be prepared for it to take a while, and you’ll absolutely need to re-sieve. As long as the plastic container they’re in is still flexible and there’s room for ice expansion, even those will survive. Continued cold under the freezing mark can make plastics brittle, but I think that’s not going to be an issue for you in San Francisco Bay Area.
A note about the article that Peter linked: if you have some solubles in your glaze, you might want to be more mindful of the temperature if you aren’t using your glaze for months at a time. You can tell if your glaze has solubles if the water that rises to the top of the bucket is not clear. If the temperature gets to about 15*c (59F) or lower, over the course of a month or so, glazes with either soluble boron and calcium, or lithium can start to form assorted solids. The lithium ones will be flat-ish, and have an octagonal or hexagonal shape. Those can be re-dissolved in hot water and added back into your glaze so you’re not changing any chemistry. Boron/calcium ones will be little round guys. I have yet to find a method of re-dissolving them. If you’ve only got a few of the borocalcium ones, they can be discarded without too much damage, but be sure to use up the full batch before adding any more ingredients to your bucket. If you remove too many, you can affect your glaze’s chemistry.
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What I mean by firing for my clay body is that instead of trying to finesse the glaze, I bisque with an eye towards a clean burn off: slow and thorough, and as Min mentioned, paying attention to a couple of specific zones. I also will go slowly in the first part of my glaze fire (up to about 700C) just to hedge bets. I fire my particular clay body hotter than the manufacturer recommends because otherwise it doesn’t meet my porosity standards. Rather than firing to a higher temperature, but I do a drop and hold schedule and let heat work push the cones over so my clay doesn’t bloat.
I started doing all of this because I was trying to get a clear glaze to actually look clear over a red clay body. The clear I was using looked great over white clay bodies and I had no problems with it even over the darkest underglazes, but I was having a heck of a time with micro bubbles over just the red clay. I’d already tweaked glaze recipe and application problems, so I started doing all the firing adjustments above. In the process I noticed that it improved the appearance of my other glazes, and gave me more consistent results all around.
Some helpful links are this digitalfire article on pinholing, and this video/article from an industrial ceramics site. Note that the last one assumes that the reader is working in an industrial setting, and adjusting the firing cycle is one of the least practical solutions. Because we’re working on a much smaller scale than that, the firing cycle is one of the first things we can look at. The digitalfire article is a good starting point for troubleshooting, and has lots of links to other helpful stuff. You’ve already gone through a bunch of it, but there are some other things it mentions, and digitalfire is a good resource to know about in any case.
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I do a bunch of work that involves combining a red clay and white slip, and what I’ve found is that when you apply it and how much water is in the slip does make a big difference in how well the 2 stick to each other. But my white clay has a lot less flux in it than yours does. I also found that firing for my clay body solved a huge boatload of glaze problems.
My inclination would be to try 3 things and see what works best. The first two are adding more opacifier to your homebrew white, and doing a bit of a line blend with your most recent iteration of the original engobe, decreasing the frit 3110 in increments of 2%.
I think what’s happening is that the engobe is melting early enough that it’s keeping your clay body from being able to offgas properly, leaving some residuals that are still trying to break loose in the glaze. Despite what they used to tell us years ago, colouring oxides do have an effect on the melt, and cobalt and copper both get moving kinda early, slowing down the release of those residuals. Iron is also melting, but it can also act as a fining agent, and it releases bubbles more readily.
A third suggestion would be to slow your bisque down, and let it soak without pushing any cones over. That should allow further off-gassing without changing the porosity of your bisque.
I don’t know if you have access to a machine like a Cricut, but if you make your stencils out of reusable vinyl, it could make them more “dip friendly.” Or maybe spraying the backs with some kind of adhesive or starch before applying them.
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@Up in Smoke Pottery and @Marcia Selsor have both been contributors to the forum in the past, although it’s been a while since I’ve seen either of them chime in. Tagging in case they’re lurking.
Marcia is probably one of the foremost obvara artists in North America, and if you get no love from any of the links here, I’d suggest reaching out to her via her website for some clarification points.
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I’ll sell seconds, but only in person so that there’s full disclosure and people can make informed decisions. Second criteria is anything that’s got cosmetic issues, but does not interfere with use, is structural, or that could possibly scratch a human or any of their belongings even slightly.
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I think there will always be people that ghost us, especially if they’re contacting via electronic means. I try to give folks pricing, terms and conditions before I start digging pieces out to take pictures of them to send. It can help weed out tire kickers. I also pointedly ask people to let me know how they want to proceed, so I’m not hanging out in limbo. There’s not a lot of tone in emails, so you have to go to direct communication tactics, rather than implied.
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I have found with red or other dark clays, a slow speed is just as good, if not better than raising the bisque temperature. It will depend a bit on your clay body. I don’t notice a huge difference between 06 and 04 bisque in the clay I use, but a slower bisque makes a noticeable difference.
- Pres, Min, Magnolia Mud Research and 1 other
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Glaze pinholes aren’t caused by organic additives to the glaze burning out. When we talk about organic burnout being a possible cause of pinholing, it’s from the carbonates/sulfates etc that are chemically bonded to the glaze materials themselves. Things like CMC, glaze additives and wax are gone and vented out of the kiln before anything starts to happen on a ceramic level. So, I don’t think you have concerns there.
As far as whether or not wheat dextrin will work to help stick the glaze to the pot or make it more brushable, it’s always worth an experiment in the name of science. As always, do a test with a small amount before adding it to a larger batch, and don’t use it on something that’s precious until you’re confident in how it'll turn out.
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If it was only the big flat things, then the most likely fix is to add a foot rim.
It’s still a good idea to do some porosity testing on that clay/glaze combo. If the clay isn’t mature, you could have issues if you want to be able to put pieces in the dishwasher or microwave. Digitalfire has some good tutorials on how to. https://digitalfire.com/test/shab
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A friend of mine who runs a paint your own pottery place uses Stroke and Coat for their underglaze colours, but she also covers all the pieces with a clear coat of glaze. Stroke and Coats can be a little on the dry/stiff side sometimes, and a zinc free clear glaze can help with that. The colours tend to be very stable, so if all you want is more gloss, that could be a very easy fix.
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On 1/2/2023 at 1:44 PM, Gonen said:
no , my question is if the metals by itself not in it oxide\carbonate form would produce the same color on oxidation firing as the oxide forms i use too ? because i think at high temperature and availability of oxygen\water it will do
So, the valence of the metal can make a difference in your glaze’s outcome, yes, but the degree that it happens to depends on the material, and sometimes the other ingredients in glaze recipe. Mostly, the oxygen or carbon atoms that are attached to the familiar colourants burn off, and aren’t part of the finished glaze at all. The purity of the source of the material will sometimes affect your outcome, and different valences of a colourant may melt differently which can also affect some glazes. Recipe substitutions are possible in many cases without having to first change black iron oxide into red iron oxide though, if that’s what you mean.
From a glaze calculation standpoint, the important thing to know is how many atoms are being supplied to the recipe by a given ingredient, and you can make substitutions if needed. For instance, you can substitute black iron oxide (Fe3O4) for red iron oxide (Fe203) in a recipe. You’ll need to weigh out less black iron to get the same effect. You can also substitute red or black copper oxide for copper carbonate. In the case of cobalt, the carbonate form supplies fewer cobalt ions to the mix, but both are powerful colourants and even small amounts of the carbonate form will give you a dark blue colour.
If you aren’t familiar with glazy.org, its a website that offers free glaze calculation software. If you want to figure out how much nickel powder you’d need to add instead of nickel oxide, you can plug your original glaze recipe in and tweak the numbers so they’re close before you begin real life testing. It saves a lot of time.
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There’s the factors that Kswan already mentioned, and all of her fixes are what I’d suggest too. Additionally, when I looked up your clay’s specs, I notice that the manufacturer lists a cone 6-9 firing range. It doesn’t seem like much, but it means that the clay won’t be fully mature at cone 6. It can create glaze fit issues that will be exaggerated by uneven glaze application, and going too fast through the wrong point in the firing/cooling. Some clay bodies also don’t like to be re-fired, with each firing creating more crystobalite in the clay. That makes pieces more susceptible to thermal shock.
In addition to Kswan’s fixes, I would suggest considering either firing the clay to maturity in one firing and using a cone 9 glaze, or choosing a clay body that has a top end maturation point of 1200C.
I find it odd that the bowl looks so similar to the other pieces in terms of thickness, but seems otherwise fine. I would do a flick test on that bowl, just to make sure there aren’t any hairline cracks that aren’t immediately visible. If the piece is whole, it will ring. If it is cracked, you’ll hear it. It makes almost a clicking sound.
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@Hulk car batteries will have lower cold cranking amps as they age, so they get harder to start in the cold. The brand and rating of the battery will also matter. 5+ years for one is pretty average in the northern climes.
I love the idea of a heat pump, but the air exchange ones don’t provide enough heat below freezing, even the ones with the snazzy defrost settings. I’d need a geothermal one because of the amount of time we spend below -15 C (5F) in a year. Retrofitting a vertical closed system heat sink is $$$$, assuming you can fit a large enough drilling truck into your back yard somehow. We simply don’t need air conditioning in the summer. Good insulation and a cross draft in the evening cools everything off just fine.
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The listing boasts of high purity, I would buy the 100g size to see how it compares. Just poking around the website a bit, it looks like they’ve got a number of common oxides that potters use, although the carbonate forms seem to be absent. The varying price point on the cobalt says to me there’s probably varying purity levels, or the mesh size might vary. If you’re okay with a slightly grainy appearance, or if you have a ball mill, this might not be an issue.
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Could just be a lifetime of accumulation, rather than a hoarding situation. My grandparents were raised in the depression, and didn’t throw anything out that could be used or reused. They had a certain amount of disposable income to buy things they wanted, in part because they often did reuse a lot of those things. Cleaning their house out after they passed took months, because we had to sort through what was useful and what wasn’t.
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@neilestrick do you know someone who could help this person out?
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Digitalfire doesn’t have it in chart form, but there is a fairly large listing of frits and their compositions. He’s starting to incorporate some information on eutectics, but I imagine it’ll be slow going. This entire website is a godsend to those with low or no budgets, and need for information.
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Another trick for accessing Adobe products (Lightroom will also resize images I believe) is to just subscribe for the free month and then cancel when you’re done. If you have trouble remembering to cancel subscriptions like this, use a visa gift card number that has a zero balance where they ask you to enter your credit card info. When they go to process the transaction in a month’s time, you’ll get a notification to update your payment info, and you can cancel or subscribe.
Advice for ware boards getting moldy?
in Studio Operations and Making Work
Posted
If your wareboards are moulding while you’re using them, you might be covering your pieces for too long. If you have to leave your pieces covered due to time constraints, put the plastic under the piece so the moisture isn’t getting to your plywood. It’ll also help to slow the drying down. If you can get back to your piece and finish it in good time, you might be wrapping it too tightly.