Extreme shivering off underglaze

[Helena1]

Hi

I have, since one year ago, gotten an extreme problem with underglaze and engobe shivering off my pieces. I don’t know how to troubleshoot the problem. 
 

I am using mainly amaco but also some spectrum underglaze, as well as mayco stroke and coat. I started off in 2021 buying amaco VUG. When the colors did not come out so vivid, I realized I need to fire lower.  I used stoneware clay fired 08 for bisque and cone 1-3 for glaze. I use transparent glaze and I paint my ware after bisque. 
 

I have always sponged or painted my ware with slip made from some leftover clay from the same clay. 1 year ago, I started experimenting with adding kaolin to the slip to make it whiter. I also started firing lower, sometimes as low as 05. This is where my problem with shivering began.  I was advised to drop the slip, paint only with the underglaze.  I was also advised to change glaze and/or clay.

I have tried 3 different white clays, and multiple  transparent glazes. I am mostly firing cone 04 but was also advised to go higher. I experimented with firing bisque higher than glaze firing, which led me to starting to bisque my work higher and also making 2 bisque fires before glaze because I thought maybe this could somehow help with the shrinking. Now I am wondering if it is making things worse? 

I once refired one of a piece that had been glaze fired to cone 04 first up to cone 5 and  noticed today the piece is shivering in edges.  (I was using  transparent glaze with wide ranges)

 Even when I went back to firing cone 1-3 like I had done before when all of this started, still some of my pieces shiver immediately after I take it out of glaze fire. One piece I tried only painting with engobe and it shivered as well.  
 

I also experienced shivering immiedately after bisque fire upon trying to paint on leather hard instead of bisque. This was however also when using a slip before so maybe it got a little bit thick with everything. 
 

I contacted amaco support advising me to use gum solution in the underglazes, as some of them were bought more than 2 years ago, I was also advised to used only distilled water which I have never done and I have mixed water directly into the jars when they seemed to be getting dry. 
 

I don’t know the outcome of the gum solution yet as I haven’t done any glaze firings. I know I might apply the underglazes a bit thick. However, I was certainly doing the same application 3 years ago and none of these pieces has shivered. I am working with ceramics a lot producing many pieces  so the whole situation is very devastating for me and I don’t know what to do!  Before I was doing basically everything the same and not experience shivering once, now it’s everywhere I look!  Can someone help me think of something I haven’t thought of yet?

[Min]

Hi Helena and welcome to the forum.

Is what you are making functional ware or nonfunctional? What is the maturing cone for the clay you are using? Is this a commercial claybody and if so could you post a link to it? Could you post a picture or two showing the shivering?

[Helena1]

Hi! Thank you so much.

i am making sculptural work, so it’s non functional. Here is an image showing underglaze amaco sea glass shivering off a piece fired to 1044/cone 05 and the clay used.  

https://www.we.no/produkt/65502114/hvit-leire-1000-1300-10kg-25-chamotte-0-0-2mm

The yellow piece is also treated with amaco velvets. It’s a different clay body,  https://www.we.no/produkt/65502101/snohvit-leire-1000-1280-10kg-uten-chamotte

 

I link the clay however they might not give a lot of information, maybe there is more about them on the package. Since they can be fired up to 1300 C according to the package maybe their maturing point would be around cone 10.

[Roberta12]

@Helena1 I had the same thing happen a few years ago.  I use a lot of underglaze on my pots, and thought I would simplify my life by underglazing the interior of cups, bisque firing, then dipping the entire pot in clear.  I would get the color on the interior without 2 glazes (interior, exterior) the Turquoise Amaco underglaze shivered off the lip of the mug on several pieces.  As did the Chartreuse.  I tried to problem solve this, to no avail.  I gave up.  When I am using underglaze in designs, it does not shiver.  It was only on the rim of those mugs.  I fired to cone 6, bisque 04, it was a Laguna porcelain.  I hope you can find answers.  

I should try it again.  I am using a different porcelain now and firing to 5.5.  Who knows?

Roberta

[Rae Reich]

I have had  some success with mixing a little of my clear base glaze into the underglaze colors.

Also, I’m not sure why one would bisque to a higher temperature when that makes the ware less porous and absorptive   Wouldn’t that tend to make the underglazes bond less well to the clay?

[Roberta12]

8 minutes ago, Rae Reich said:

I have had  some success with mixing a little of my clear base glaze into the underglaze colors.

Also, I’m not sure why one would bisque to a higher temperature when that makes the ware less porous and absorptive   Wouldn’t that tend to make the underglazes bond less well to the clay?

I wonder if it was because it was porcelain that I had the issue. less porous and absorptive. I may have to revisit this situation.  

[neilestrick]

Since it is happening with different colors of different brands, and different glazes, the problem is not with the underglazes or the glazes themselves, but rather the clay. When you say you've used 3 different white clays, what is the max firing temp for those clays? Were they all rated to 1300F? If so, that may be part of the problem. Using a clay that is made to mature at the temperature you're glaze firing to may solve the problem. When glaze firing to cone 05, were you using a body specifically made for low fire?

Does the underglaze shiver if i you don't put a clear glaze over it? 

Adding kaolin to slip is problematic, and adding slip at the wrong time (too dry) can also cause problems.

One other possibility, do you have lotion/moisturizer on your hands while touching the bisque? I've seen that cause crawling, but I suppose it could also cause shivering.

[Rae Reich]

In addition, rims are usually compacted more in throwing. 

[Helena1]

@Roberta12 ive also had problems with chartreuse which is an  shame because I really love that color! But it’s also been happening with amethyst, turqouise, blue, orange, maroon… to mention a few. Since it’s happening so much I feel like it’s some overall problem that I don’t see. I will also try to fire higher and be more aware of the texture of the underglaze, stir it more frequently and use the gum solution when I get a hold of it. But it’s a very bad feeling not being able to pinpoint the fault! If one piece shivers I feel like more might do it as well with time
 

@Rae Reich thank you, I will go on and try this as well. I started bisque fire higher than the glaze because I read this in a mayco spreadsheet about shivering. If I use a commercial brush on clay it’s not hard to adhere the glaze, but maybe you have a point in this is only making the bond worse because I feel like all my experiment is only leading to more shivering… some of my pieces get fired 3 times now and maybe it’s just a waste of time as well as the bonding part!

 

@neilestrick they all fire to be mature/vitrified at a higher cone. Unfortunately my supplier don’t have much to offer for a more low fired clay. They offer earthenware without chamotte, i would prefer it with since I hand build a lot. I read somewhere that earthenware don’t really mature anyway so I thought it wouldn’t make a difference to use stoneware. I am also reluctant to earthenware because of the damage it could do to the kiln if I get it wrong :S

I have seen the underglaze shiver off bisque in some pieces as well, when I was trying to apply UG in Leatherhard stage. But some of these pieces where using a commercial slip from another brand as well so that was for sure part of the problem. But it seems to be continuing still as my latest shivering piece didn’t have the engobe. I painted it white though, using the white UG from amaco, and added more colors after bisque. It probably came out to thick, but I feel like I’m not sure about this either as I feel like I have always been painting underglaze somewhat heavy since i started using them. 

[Min]

27 minutes ago, Helena1 said:

They offer earthenware without chamotte, i would prefer it with since I hand build a lot

This would be a better choice, you can always wedge in some chamotte/grog.

[Helena1]

@Min yes i will  probably have to at least try it to see if it helps! Thanks

[oldlady]

helena, i noticed that you referred to several cones beginning with zero.  are you working with stoneware or porcelain?    do you have access to a chart that tells you the temperature associated with those cone numbers?   i ask because so many people have been confused and think a higher number following the zero is hotter than the lower numbers.  there are some earthenware clays that are bisqued to 06 and fired to 06 but stoneware finishes much hotter because of its higher density.

the numbers read from  high (cool)  numbers upward to zero and single digits upward toward very high (hot).   my stoneware is mature at cone 6 and i bisque at cone 04 to burn out impurities, the temps are approximately 2240 for cone 6 and about 1850 for bisque 04.   (books out in the studio with accurate #s.)

[oldlady]

just FYI, slip made from the same clay as the body of the pieces you make works very well while the piece is still damp from forming.   clay slip soaks into the clay body then but it cannot do that once the piece has dried.

if you read the labels you will find that stroke & coat is a glaze, not an underglaze.

 

[Kelly in AK]

Shivering is generally considered a clay body problem, the exception being one glaze out of many that shivers while the rest fit.

With slip (the added kaolin is not helping), underglaze, and glaze, you’re working on making four things play nice. If you’ve dropped the slip, you've narrowed it down.

The application and gum are unlikely to be the source or solution of your problem. Adhesion at room temperature counts for very little in this equation. It’s the clay bodies. Wildly different coefficients of expansion from either the glazes or the underglazes. Continue eliminating variables, you’ll solve it. 

[PeterH]

2 hours ago, Kelly in AK said:

 With slip (the added kaolin is not helping), underglaze, and glaze, you’re working on making four things play nice.

Re-reading Digitalfire the second paragraph seems relevant..

Glaze Shivering
https://www.digitalfire.com/trouble/glaze+shivering

Shivering is the opposite of glaze crazing, the fired glaze is under compression and wants to flake off the body, especially at edges. However the route cause is a mismatch in the thermal expansions of body and glaze, thus the process of resolving it is similar as for crazing. It it much less common because glazes tend to have a higher thermal expansion than bodies and because they can tolerate being under compression much better than being under tension. Of course, if a glaze is under compression on the inside of a vessel, the body will be under tension and this can cause failure of the piece.

When the body-glaze interface is not well developed an overly compressed glaze will be able to release itself much more easily, especially on the edges of contours. This can be the case, not only with low fired ware, but where engobes or slips are being used under the glaze. If the engobe does not contain enough flux to firmly adhere it to the body and develop hardness, it will not be able to bond to the glaze well.

PS Time for some rim-shaped test-tiles?

Edited May 2 by PeterH

[Min]

On 4/28/2024 at 4:18 PM, Helena1 said:

It probably came out to thick, but I feel like I’m not sure about this either as I feel like I have always been painting underglaze somewhat heavy since i started using them. 

It might just be as simple as thinning down the underglaze with water and applying 2-3 coats to get the opacity of colour you are looking for. If underglaze is applied too thick it can definitely lift from the clay. 

What works for me is putting the first coat on fairly thin then when that layer is dry I apply another 2 coats to get an opaque coverage. I mostly use Spectrum underglazes but have also used Crysanthos, Velvets, Speedball, LUGs and homemade underglazes.  The only time I don't water an underglaze down is when doing an underglaze transfer.