Problems with Highwater clays!!??
I have been told that a bunch of potters are having trouble with Highwater Clay (Phoenix and Orangestone) dunting after firing. (Cynthia Bringle and the Penland class, Jon Ellenbogen, Leah Leitson, etc).
Just wondering if anyone else is experiencing problems.
I assume it is related to Custer Feldspar loosing 2.5% potassium (went from about 10% - about 7.5%) but unsure if it is because it is in both the clay and the glaze or just a clay body problem?
Let me know so I can see if there have been any solutions found.
Here is an article on the subject if you are interested:
http://www.ronroy.net/analyses/custer-article-.pdf
Just wondering if anyone else is experiencing problems.
I assume it is related to Custer Feldspar loosing 2.5% potassium (went from about 10% - about 7.5%) but unsure if it is because it is in both the clay and the glaze or just a clay body problem?
Let me know so I can see if there have been any solutions found.
Here is an article on the subject if you are interested:
http://www.ronroy.net/analyses/custer-article-.pdf
Comments
The clay at Highwater has has issues since they moved to the new place. All it takes is supervision and attention to detail, not that hard of a thing to do.
It could be related to the Custer changing and since that whole situation is in flux it may take a while to shake out. That is because Pacer is only selling 325 mesh Custer in the future and that means that it may not be used in clay bodies anymore (too fine).
But not sure.
Clearly some glazes have been effected and will be in the future but we can use Custer 325 in glazes. And if a clay body has insufficient flux and the glaze is also under fluxed it can cause cracking. the Custer has less potassium and using the new custer can cause the COE/CTE to change.
So I am trying some STARWORKS clay and people may just have to switch to Laguna or Standard or Starworks to fix the problems. (I haven't heard of any problems with their clays)
http://futurerelicsstudio.blogspot.com/2014/06/the-good-and-bad-of-wood-firing.html
At the time of writing we didn’t know what was causing it but had a lot of discussion trying to figure it out.
I was also the studio assistant for Cynthia Bringle this spring where we saw the same issue. The most disturbing part was how the pieces might not break until a few days later even when sitting undisturbed on a shelf.
I’m testing some clay from Stone Mountain Clay right now to see if it suites my needs.
It is my understanding that all clay manufacturers are having the same growing pains as they transition to using a different feldspar in their formulas.
The people at highwater were very helpful in trying to fix the problem.
Don't make glaze changes! IT is the CLAY and they should take it back or I would just throw it way. The time and money spent to fix the problem is outrageous and simply getting a product that works is what you paid for. Get the clay from someone else and pay the shipping! It will cost less than have uncertainty and breakage and lies and you will go out of business. Are you on Facebook? I want to post your letter so other can see what is happening. Otherwise Highwater says that it is isolated when we can see that it is not!
I have been using Aurora from Highwater for the past several years, Trina Buff for years before that. I make primarily functional pieces and fire to Cone 10 in a new 52 cubic foot natural gas-fired car kiln. My pots are bisqued to 07. The glaze firing cycle is 8 hours. Before building this kiln a few months ago, I was firing in a similar kiln fired with propane in a 12-14 hour firing cycle. I've had the same problem with both kilns and firing cycles.
The loss of pots, work, and sales certainly stings, but I also worry about the longer term problem of a ruined reputation if customers get hold of pots that break spontaneously under normal use. That's the kind of thing that puts companies out of business.
If this is a custer felspar issue, then it is likely industry-wide. I imagine the larger companies are better able to address the issue with modified clay formulations so I'll be looking into getting supplied by Laguna, Standard, etc.
This is the problem with deciding what the cause is. Some people use a huge variety of glazes and don't really know what they are doing while others have been using the same glazes and clay for over 40 years.
When I talked to those people (40 years in business!) and they had problems and Highwater was discounting their accounts of problems with clay - then it is clear that there is a problem and Highwater doesn't want to talk about it.
Don't you think it is strange the Highwater won't come on this blog and address the problems? They say nothing!
So, yes a difference in the CTE of a liner and the outside glaze may make a difference, as will the thickness of a pot.So thin pots will definitely have this issue because of no structure to support the pot while thick pots won't show the problem.
But the problem with Highwater clays isn't a glaze issue it is a clay issue.
Thanks for writing in! I would still be see curious to see the thermal expansion of some of theses glazes. As materials change it is likely causing the thermal expansion of both the glazes and clay to change. Julie at Standard says that the thermal expansion for 257 grolleg is 5.72. However a glaze with a thermal expansion of 6.66 is destroying thin pots. (Applied thin at a specific gravity of 143) Julie sent me a recipe that was formulated and tested for 257 grolleg 5 years ago that has a thermal expansion of 6.63 and based purely on the numbers would be likely to break pots. I have not tested her recipe, but would all of this this mean that the thermal expansion of the clay is more likely to actually be in the range of 6.5-7?
Running with my speculative theory of higher thermal expansion in clay bodies, could this be a contributing issue at the root of your example of 40 year glazes and new clay problems?
Don't get me wrong, highwater clays certainly have major x10 issues that they are not addresing. So many issues that I switched clay companies!
I have glazed the pots entirely with this glaze without issues. It is when I use the CTE of 6.66 glaze as a liner and a copper red that crazes on the outside that I am having my issues. I have fired the same glaze combination to cone 10 in both oxidation electric and gas reduction kilns with equally bad results.
When I switched from p10 to 257 Grolleg I had to reduce the specific gravity of my some of my glazes. The 257 matures at a much lower temperature and my copper red glaze was melting off the pots. I have fired the 257 to cone 12 without issues. Just keep it on a flat surface and don't use wads because the pots deform over the wads and warp if placed over the edge of the shelf as low as 10.
The solution to my broken pots with Julie is simply to keep all liner glazes at CTE of 7 or above. I am really curious if part of the issue may be that the CTE of the clay is closer to the 6.5-7 range instead of the published 5.72 for 257 Grolleg. What do you think?
Kyle
I do know of someone with one particular standard clay body that had similar issues only with that particular number clay. I believe it was 378....she had all the pieces dunt from that batch of 378 following woodfiring to cone 10. And in confirming that number on Standard's website, I see they have issued a statement regarding some of their clay bodies and the change in the feldspar. They are suggesting folks glaze test before using those bodies.
I will no longer be buying clay from companies that uses Custer feldspar. Custer is an unreliable product that wildly varies in composition. It is not completely the fault of the clay companies that they are having issues, yet they still choose to use Custer. Actually I take that back, it's their fault for continuing to use Custer!
I really "liked" Highwater and used to exclusively use their clays. I am afraid that this is going to put them out of business.
Just looking at clay options here... (please feel free to add to this list!)
-Reliable companies using some form of g200-
Aardvark
Laguna
-Companies using custer-
Highwater
Standard
Glad you are figuring our your problems. I agree it is their fault for using Custer and not fixing the issues. That is their job...when you make clay ...that is your job. Denying the problem doesn't allow them to fix it, since there is no problem. What they need to either get a technical/ceramic engineer to help reformulate the body with custer or use G-200 EU . It may cost more but then you just charge more. If the clay works we will buy it.
We are all in the same boat and want to just make stuff that doesn't break! I loved Highwater too as does everyone but if they deny, blame and hide then they will never fix their problems. And they will not regain the old customers because of the way that they treated them!! A clearly stupid approach to customer service.
Thanks again for your reply.!
Another factor to consider may also be the mesh size of the feldspar they are using. Standard clay has posted information regarding their clay bodies and the new shrinkage/absorption they are noting as a result: http://www.standardceramic.com/CusterChanges.html
Denise
I glazed some of the Coleman Porcelain mugs with a liner glaze that I had previously believed was breaking Standard 257 mugs due to its low thermal expansion of 6.66. These pieces also survived boiling water and being promptly dunked in cold water.
My personal recommendation would be to find out what feldspar your clay company uses and avoid any company that uses Custer Feldspar. At least until they switch to g200/HP/EU or Minspar. The composition of custer varies too much to be reliable in a clay body.(http://www.ronroy.net/analyses/custer-article-.pdf#original)