Oribe Glaze Shivering on Standard 192 clay

[Wilboy64]

Need a little input on a issue we are having with a new clay to us. 

I will try to give as much information as possible and would greatly appreciate your help. My wife and I have been making pottery for over 8 years. We started out using Highwater 306 ,153 and Standard 108 and over the years tried others from Starworks.  We use a range of glazes we mix ourselves. Our glazes have been borrowed from other potters' and have been very good to us over the years.(Tenmoku. Iron Red, Hayden Red. Egg shell.)  This year we tried some different clays from Standard Clay.   (181, 182, 192. 378)    We are wondering if anyone has had any issues with the Standard 192?  We have always bisked at cone 04 and fired electric oxidation to cone 8.  That being said we fired a group of wares with our Oride glaze with the formula as follows:

Custer felspar 29.3%,  Silica 24%, Whiting 21.2%, Talc 7.4%, EPK 11.9%, Bone Ash 1.0%,  Black Copper Oxide 5.2%

We noticed as the wares were cooling  right out of the kiln and then up to a week later sitting on the shelves in the studio that the Oribe glaze on the wares made of 192 clay started shivering. We also had a couple of mugs with Egg Shell glaze made from 192 clay that had a couple of handles that had spots that shivered .   We see no problems with other glazes on clays other than the 192.  We did have some pieces that we used the Oribe on other than the 192 and it appears we have no issue with them. We even put them in the freezer and then shocked them with hot water and no cracking or shivering has occured on them.

Question, Do we ditch the  Standard 192 or do we change our glaze? How can we feel we have made a safe choice?

 

 

 

[Min]

Looking at the chemistry of the glaze using Insight, your Oribe has a COE of 6.52 which is pretty much in the middle range for COE's. If you want to keep using the Standard 192 you would have to increase the COE of the glaze, take out some of the talc, increase the custer and re-balance the silica and alumina. Would take some testing to do, glaze chemistry software would make the job easier. Altered glaze might look a bit different from the original. Do you have a gloss glaze that doesn't shiver on Standard 192? Could compare its COE figure with the Oribe one so you would have a ballpark target COE to aim for. If some of the Standard 192 pots shivered with Oribe I wouldn't trust any of them. BTW have you tried leaving a lemon slice on the Oribe for a couple days?