Mudfish
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Posts posted by Mudfish
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Custer 48.3
Epk 25 (used calcined for a third of this)
3.8 parts whiting
Original formula called for 22 parts dolomite, which I subbed the talc/bone ash, because I am out of dolomite.
Also, I added 3 percent manganese carb, and 3 percent titanium.
It shivered on the rim of a few mugs, and I'm assuming it was from a light application of white slip that I applied at the greenware stage
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Yes, it must have been the talc, and yes, I got a 5 gallon bucket full. Is there anything I could add that might help?
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No, the glaze that shivered is not a matte. I subbed the 22 parts dolomite in the formula with 10 parts bone ash, and 12 parts talc. The rest of the formula called for 48.3 parts custer, 25 parts EPK, (which I used about half calcined Epk for that), and 3.8 parts whiting. I'm just guessing that it was the materials I subbed for the dolomite that made it shiver, and it was also much more glossy than I expected
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out of dolomite at the moment and looking for a good matte/satin matte white-ish base glaze. Does anyone have any insight into this cone 10 glaze "Horsely's Satin Matte White?
* Custer 49.19
* Whiting 29.95
*Om4 21.62
* EPK 3.24, Zirco 12%, Titanium 4.8%, zinc 4.8%
How does this formulation react over colored slips, especially? I sometimes have trouble with shivering. Shivering happening on rims and over slip/colored slip applications. I use stoneware. Standard #153, cone 10, and sometimes I use Standard stoneware white #181. Thanks, everyone
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I have an Estrin Clay Mixer and would like some advice on how to remove rust from the blades and the bin area. I have used it and the motor works great, but the rust chips off in the clay and makes throwing not so smooth, plus these rust chips melt right through the glaze and leave ugly splotches.
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continued success with these large platters. Thanks again to all
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Any advise out there about good pop up tents and suggestions for how to weight them securely? I have been using a Show Off and pro panels, but it is just so labor intensive to set up by myself - I feel like I've been through boot camp by the end of a weekend show. I've heard that some pop ups will not work with pro panels, and of course, the nightmare stories of pop ups becoming large kites during high winds. Thanks
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Just unloaded the kiln today and to my great relief these platters have NO cracks ! I'm so happy to be batting a thousand this go-around. I hope these results continue. What I did was to lift the bottom edge while throwing these forms to round out that area, omitted the grog, paid more attention to closing up damper for the cool down, and I fired on a fairly thick bed of silica. Thank you all so much
- Babs, Callie Beller Diesel, Hulk and 4 others
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On 3/30/2023 at 8:23 PM, Bill Kielb said:
Just some things that strike me
For cracks happening at bisque, I would look for production techniques and handling prior to. Grog has never really helped me develop much extra strength. It generally Does open up the body.So cracking at bisque when the body is just being sintered maybe very telling
For production I would always start with compression, real compression not just pushing down though. For bottoms, out to inward ribbing, not so much in to out …….. rims - ok, push down ……… walls - ribs are great. I would also not over work during the trimming stage, hard to do with lots of grog, I get it. Are we adding grog for appearance and is this creating weak areas for cracks to originate? Well mixed - homogeneous? Gently ring your bisque, often hairline cracks can be discovered at this point.For firing, I would definitely make sure it was constructed well and for sure, make sure it can slide easily on the kiln shelf which means silica or alumina or something to let this grow and shrink in all directions. In its present form it looks fairly rough maybe due to the grog so getting this right might take some doing. Your last picture almost looks like there is a shelf pluck mark, top right.
it would be great to examine the bottoms of all these to see if the rough multiple foot rings likely contributed to some of the failures.
I would start with the cracked bisque though, this may be telling you something.
Thanks, Bill I will pay more attentiion to trimming and making the bottom smooth. I will abandon the grog idea. If cracks are happening during the bisque, they are too fine to notice, and they expand in the glaze fire. Cracks have happened during the bisque firing, but it is hairline cracks that are visible, so I don't continue on with glazing. Maybe all of these cracks are happening during the bisque firing and they just are not visible until the cone 9-10 temps
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I will try this idea also. A couple of years ago, I did try a version of your idea, here. I don't remember flipping the slab over to rib both sides, though. Anyway, the form ended up cracking all around the join as it was drying. I abandoned the idea but maybe I should have kept trying.
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Thanks, Babs. Yes, I do support these forms when I flip them over to dry. I use sponges, soft cloths..,etc. to support the center so they won't sag. I turn the forms often, and keep them loosely covered so that they dry evenly. I think I will omit using grog as I don't think it is helping. I will look for the book you suggest - I'm sure its on Amazon. I have made several more of these forms, but with a more rounded bottom edge, as Pres suggested. I'm hoping that is a solution to the problem. I will probably be bisque firing them with my next kilnload in about a week and I will let you all know if they survive the bisque fire
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Marc C. I do fire down in hopes the wares will cool off slowly and avoid these cracks. Also, I use a slow cool to avoid pinholes and to assure the glazes stay matte. My kiln is a downdraft, 9cubic ft. I really feel like I compress enough both ways - outward to inward, and vise versa.
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5 hours ago, Retxy said:
I'm a newbie here with glaze formulation constantly on my mind. I noticed some shivering of your glaze where the base rises into the sides of your platter... Are you sure this is not from a glaze fit issue? Does it happen with all your Glazes or just this one? I'm SO sorry, I know your pain.
yes, the one platter does have some crawling - probably too much glaze was sprayed on.
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Jeff. I will pay attention to the grog additions, as I really dont measure, just kind of sprinkle. As for the water usage, I see where that would cause shrinkage/cracks also. If I ever get this problem resolved, I will post pics of my work without the hideous cracks! Thanks everyone
- Jeff Longtin and Rae Reich
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thanks, Pres. I have one of these forms on the wheel right now, and its at a stage where I can lift the outer base to a rounded rise. I will give it try. I have made smaller diameter platters with a more rounded rise and had no problems with cracking, so maybe that is the remedy. Appreciate your help !
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I have tried all the suggestions I have read on here about this topic. coils, cookies, sand, grog, even a "heat sink" idea that I read about on this forum. I still get cracks during the cone 9-10 reduction glaze firing. Sometimes cracks happen during the bisque firing also. With the last firing, I programmed in a slow cool - 100f per hour to 1500f, however, the controller apparently errored after that and shut the pilot off for the rest of the slow cool program. When I caught the error at 700F, I closed the damper hoping to retain enough of a slow cool so cracks would not happen. I am guessing the cracks are happening during the cooling since the glaze is not melted down into the cracks. What is a good slow cool program? Thank you al
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I make a lot of these dog-dish type of forms. Some are as large as 16" diameter. Not all of them crack like this, but it sure is a heartache when it is a large piece that is cracked. Sometimes the cracks develop in the bisque fire also. Some are "s" cracks and some are razor straight. I have tried to elevate firing these forms on wads of clay to distribute the heat from the kiln shelf but they get warpy. I really do not think it is a compression issue - I'm obsessive about that. I am thinking its possibly an issue with either uneven drying in the greenware state, or it is an issue with a large surface exposured to the kiln shelf that is so much hotter than the kiln atmosphere during the cooling cycle of the firing. I know cracks can develop and not be evident until the glaze firing. I have not been doing a slow cool with the bisque fire, but I'm thinking this would help. Thanks
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Yes. Callie. It's more the reactive qualities of tin that I love. So I'm trying to come up with economical ways to use tin
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was wondering if anyone recommends or uses a tin oxide wash. I can find formulas for all kinds of washes, but never one for tin oxide, maybe for good reason. So, yay or nay on the tin oxide wash?
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Ok, Thank you, Callie. I have some Flamingo Pink underglaze from Laguna. I will try this under my clear glaze.
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Was wondering if I use a Zircon-Cadmium Bright Red Stain in amounts less than 5% will I get pink instead of red. Glazing tomorrow and I'm out of tin to make chrome tin pink. Out of titanium also. I fire to cone 8/9 reduction. Thanks
Glaze insights into Horseley's Satin Matte White
in Clay and Glaze Chemistry
Posted
Thanks, Min. This glaze only shivered over the rims that had the slip application. So, my next question, are some slips more compatible with various glazes than others ? Also, is it better to formulate slip/colored slips using my clay body slurry? This seems like a solution to me