PeppernPatches Posted April 10, 2018 Report Share Posted April 10, 2018 Hello everyone! I am stumped on this issue and was wondering if anyone had any insight or advice on this. We opened our soda kiln a couple weeks ago and I had a problem with my work. I fired 64 pcs, most of which was Rods Bod clay body which also had some Red Iron Oxide slip decoration on it. I used Penn State Shino that I mixed the day that I glazed. 60% of it had major shivering! The glaze was just crumbling off and some thicker areas coming off in large pieces, leaving a grey stony finish behind. Such a bummer! See video here: https://youtu.be/0cbd0eXvYII Some things to note in this firing: - No one else's work shivered, but no one else used Rods bod or PSS Shino. - Pieces from previous firing that didn't make it in kiln and fired this time were ALL okay. They had been sitting for 6 wks and were Rods Bod with RIO decoration and PSS glaze. - I fired over two dozen spoons with Takamori clay body and PSS glaze, and NONE of them shivered. There was some crazing. - All my Rods Bod pcs with SF Shino or other glazes did not shiver. - 5 sake cups that fired cold didn't shiver. - There was crazing on several pieces. - Areas that got hit with a lot of soda on Rods Bod/PSS would shiver. - I did rush the drying process of Rods bod, drying in the sun and did a 2 hour pre-heat when I bisqued. I never had a shivering problem with Rods Bod and PSS glaze until the last two firings, which make me wonder if it's a clay body issue, a combo of clay body and glaze fit, or something happened in the glaze mixture. Or could it be the soda ash? I did find a discrepancy in our PSS recipe vs. the one from Liz Willoughby when I double checked today; we use 4.9 OM4 amount instead of her 14.9 OM4 amt, and I wonder if that makes a difference in anything. SODA ASH SPRAY RECIPE 1 lb soda ash to 1/2 gal water PENN STATE SHINO RECIPE - LIZ WILLOUGHBY 14.6 Neph Synite 7.8 Soda ash (light) 9.7 EPK 4.9 OM4 34.0 F4 feldspar 29.0 Spodumene Link to comment Share on other sites More sharing options...
Callie Beller Diesel Posted April 10, 2018 Report Share Posted April 10, 2018 I'm going to venture that it is likely a glaze batch problem. Leaving 10% of your clay out is definitely going to affect the recipe, because you're missing a statistically significant percentage of your silica and alumina. Even without looking at glaze calc software, that leaves the recipe really oversupplied with all kinds of sodium flux, which would be exacerbated by adding yet more sodium of any kind when you sprayed. Sodium has a high coe, so the resulting shivering is logical. Link to comment Share on other sites More sharing options...
Min Posted April 10, 2018 Report Share Posted April 10, 2018 Is the shivering only over the pots with iron oxide slip? Wondering if the slip bonded to the underlying claybody. Link to comment Share on other sites More sharing options...
PeppernPatches Posted April 10, 2018 Author Report Share Posted April 10, 2018 6 hours ago, Min said: Is the shivering only over the pots with iron oxide slip? Wondering if the slip bonded to the underlying claybody. Hi Min, No the shivering is happening on areas on a couple Rods bods vessels that had no slip on it. Link to comment Share on other sites More sharing options...
PeppernPatches Posted April 10, 2018 Author Report Share Posted April 10, 2018 6 hours ago, Callie Beller Diesel said: I'm going to venture that it is likely a glaze batch problem. Leaving 10% of your clay out is definitely going to affect the recipe, because you're missing a statistically significant percentage of your silica and alumina. Even without looking at glaze calc software, that leaves the recipe really oversupplied with all kinds of sodium flux, which would be exacerbated by adding yet more sodium of any kind when you sprayed. Sodium has a high coe, so the resulting shivering is logical. Thank you for your insight Callie, much appreciated. I'll run some tests with the recipe that has more OM4 in it! What is COE? Link to comment Share on other sites More sharing options...
terrim8 Posted April 10, 2018 Report Share Posted April 10, 2018 coefficient of expansion - but the answer about leaving out 10% of the ball clay OM4 is the biggie! It's like leaving out the eggs in a good cake recipe- the cake will be dry and fall apart. State Penn or Penn State? Link to comment Share on other sites More sharing options...
PeppernPatches Posted April 10, 2018 Author Report Share Posted April 10, 2018 4 minutes ago, terrim8 said: coefficient of expansion - but the answer about leaving out 10% of the ball clay OM4 is the biggie! It's like leaving out the eggs in a good cake recipe- the cake will be dry and fall apart. State Penn or Penn State? That's a great analogy! It's Penn State Shino:) Link to comment Share on other sites More sharing options...
terrim8 Posted April 10, 2018 Report Share Posted April 10, 2018 I know- I've just been waiting to say that to someone about that glaze Link to comment Share on other sites More sharing options...
PeppernPatches Posted April 10, 2018 Author Report Share Posted April 10, 2018 If it is the OM4 discrepancy, then I wonder why it didn't shiver before in previous firings? Only in the last two firings, and only in combination with Rods bod clay. Does anyone recommend a better Shino recipe for soda firing? Link to comment Share on other sites More sharing options...
Magnolia Mud Research Posted April 11, 2018 Report Share Posted April 11, 2018 this is the Shino I use at cone 10. Water/solids ratio is ~0.7 weight ratio. Crackle, yes on some clay bodies. Never observed shivering. component % wt Soda Ash 8.1 Neph Sy 39.3 Spodumene 30.6 OM4 17.2 EPK 4.8 Total 100 LT Link to comment Share on other sites More sharing options...
Mark C. Posted April 11, 2018 Report Share Posted April 11, 2018 Leaving the clay out is just asking for issues-thats one thing I would say straight away . Rods bod is a high silica content body so that would also point to some issues Shivering can also happen later so keep an eye on those yet to shiver down the road and do not sell them. The crazing is showing you an issue -the shivering is screaming at you an issue. The glaze thickness also looks really thick as well which also could be an additional issue I might change bodies or test a new body and mix the glazes with the right amounts next time for sure.When making glaze double check all the measurements at least twice. Link to comment Share on other sites More sharing options...
PeppernPatches Posted April 11, 2018 Author Report Share Posted April 11, 2018 On 4/10/2018 at 6:29 AM, Min said: Is the shivering only over the pots with iron oxide slip? Wondering if the slip bonded to the underlying claybody. Hi Min, Actually I did make a NEW batch of RIO slip for the last two firings which had the shivering. It was a different recipe from the one that I used before. Here's the difference: Fish Sauce Grolleg Porcelain 43.8 Minspar (200) 23.5 Silica 15.6 Bentonite 9.4 Pyrax 7.8 Red Iron Oxide 15 New RIO Slip EPK 50 Silica 35 Custer Feldspar 25 Bentonite 2 Gersley Borate 10 RIO 15 However, a few pieces of mine had no RIO slip decoration on it, and they still shivered. I'm not very knowledgeable on glaze chemistry and so really appreciate your input and have always enjoyed reading your posts! Thank you! Link to comment Share on other sites More sharing options...
PeppernPatches Posted April 11, 2018 Author Report Share Posted April 11, 2018 17 hours ago, Mark C. said: Leaving the clay out is just asking for issues-thats one thing I would say straight away . Rods bod is a high silica content body so that would also point to some issues Shivering can also happen later so keep an eye on those yet to shiver down the road and do not sell them. The crazing is showing you an issue -the shivering is screaming at you an issue. The glaze thickness also looks really thick as well which also could be an additional issue I might change bodies or test a new body and mix the glazes with the right amounts next time for sure.When making glaze double check all the measurements at least twice. Thank you Mark! I will definitely do that and study up more on this. Since I like Rods bod so much, I think it's best to change to another type of Shino for soda firing. Link to comment Share on other sites More sharing options...
PeppernPatches Posted April 11, 2018 Author Report Share Posted April 11, 2018 17 hours ago, Magnolia Mud Research said: this is the Shino I use at cone 10. Water/solids ratio is ~0.7 weight ratio. Crackle, yes on some clay bodies. Never observed shivering. component % wt Soda Ash 8.1 Neph Sy 39.3 Spodumene 30.6 OM4 17.2 EPK 4.8 Total 100 LT Thank you! Much appreciated. Is there a name for that Shino? Link to comment Share on other sites More sharing options...
Min Posted April 11, 2018 Report Share Posted April 11, 2018 I think the lower ball clay is a red herring. John Britt recipe has OM4 at 4.9 Nan Rothwell transcribed from Liz Willoughby, cited in Studio Pottery Magazine June 2002 incorrectly and uses both versions of 4.9 and 14.9 (near the bottom of the page). Low ball clay recipe compared to LT's recipe isn't much different, screen shot below, look at the box in the lower right corner. Your recipe is #1, LT's #2 Link to comment Share on other sites More sharing options...
Magnolia Mud Research Posted April 12, 2018 Report Share Posted April 12, 2018 6 hours ago, simatai33 said: Thank you! Much appreciated. Is there a name for that Shino? The name is Shino # 1. it seems to have been originated by Unknown who wrote the recipe on the 5 gallon bucket. I have no information of the source of the bucket. Link to comment Share on other sites More sharing options...
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