Shelves

[Rebekah Krieger]

The shelves I have are in horrible condition (they came with the kiln) They appear to have a light coating of glaze (shiny) covering the entire surface.  There is a lot of glaze dripped everywhere as well. I was always pretty anal with my own shelves, and never had anything on them. How do yours look and what is "too bad" to save? Can I put a coating of kiln wash over small specks of glaze or do they have to be perfect to get the wash? I am going to buy a new set of shelves today because I don't see this being less than a week's worth of work to get them useable. I don't even understand how the person was able to use these.  

[neilestrick]

Grinding shelves can be a lot of work. Sometimes it's just not worth the time to deal with it. Glaze drips that won't come off easily can be covered with wash and fired again. The wash will soak in and make it easier to chip the glaze off. Little specks of glaze can just be covered over with wash and forgotten.

[Mark C.]

All old glaze and loose wash needs to be ground off and smooth befor new wash is put on.

There has been a lot said here on this as to how to grind them-you may want to search for those posts.

Electric kiln shelves are pretty cheap-if you buy new get those honey combed ones that hold up from warping better.

Mark

[Norm Stuart]

The person who previously used your shelves almost assuredly used a kiln wash of 50% Silica and 50% Kaolin.  If you use 50% Alumina Hydrate and 50% Kaolin you don't end up with these problems.    http://jeffcampana.com/self-leveling-kiln-wash/

 

The shelves should be ground down, but it's a huge messy job.  In the interim, you can apply a fairly thick layer of kiln wash like Jeff Campana's to avoid your ware sticking to the glaze, but it's not going to make the shelves level.

 

The shelves I have are in horrible condition (they came with the kiln) They appear to have a light coating of glaze (shiny) covering the entire surface.  There is a lot of glaze dripped everywhere as well. I was always pretty anal with my own shelves, and never had anything on them. How do yours look and what is "too bad" to save? Can I put a coating of kiln wash over small specks of glaze or do they have to be perfect to get the wash? I am going to buy a new set of shelves today because I don't see this being less than a week's worth of work to get them useable. I don't even understand how the person was able to use these.  

[Guest JBaymore]

In my 45 years of doing this craft, I've used 50% kaolin (EPK) and 50% 200 m flint for YEARS in gas kilns....... and it does not get "glassy".

 

With a chemical analysis like this......... even with the repeated heatwork of multiple firings........... not going to melt to a glass.

 

Silica...................... 50.00
EP Kaolin................... 50.00
=========
100.00

CaO 0.27* 0.10 0.11
MgO 0.21* 0.05 0.09
K2O 0.30* 0.18 0.12
Na2O 0.08* 0.03 0.03
P2O5 0.14* 0.13 0.06
TiO2 0.39 0.20 0.16
Al2O3 30.90 20.18 13.03
SiO2 204.54 78.70 86.21
Fe2O3 0.42 0.43 0.18


Si:Al: 6.62
Thermal Expansion: 4.20

 

 

Take the shelves to the local place that is likely associated with an auto repair facility........ that does sandblasting.  If the shelves are clay type.... tell them to take down the surface until it is all just beige.  If they are silicon carbide, tell them to take it down until it is sort of black.  And so on.  Won;t be very expensive, that is the tool for the job, and they can handle the toxic dusts.

 

I HAVE seen people make the mistake repeatedly of using an unlabeled bucket of "white stuff" that they thought was kiln wash.... and glaze their shelves! 

 

 

best,

 

.........................john

[Norm Stuart]

John - your skill set is far too advanced.  Mere mortals deal with problems which might horrify you - like people who use a shrink ruler to measure the distance a thermocouple extends into a kiln.

 

When you run a studio filled with amateurs who apply far too much glaze you need to use a kiln wash of 50% alumina hydrate and 50% kaolin. 

 

The problem with using a kiln wash of Silica instead of Alumina is free-running glaze enables the silica to join the glaze melt.  The result is you use a hammer and chisel to remove the glaze rather than simply lifting the ware and attached glaze run off the shelf.

 

Even when this doesn't happen, some glazes like the copper heavy Philadelphia Green glaze mist onto the shelves around them.  With an alumina hydrate kiln wash you don't even really notice this - but with a silica based kiln wash, repeated firings with misting glazes without reapplying new kiln wash will build up a gloss on the top of the silica based kiln wash.

 

Your analysis of the refractory nature of silica combined with kaolin is wholly accurate if you fire an empty kiln without ware.  The glaze on the ware begin to contribute a wide variety of fluxes to the silica kiln wash, and added flux change silica and kaolin from a refractory to a glaze.

 

For most of us, alumina is a gift from the gods.

In my 45 years of doing this craft, I've used 50% kaolin (EPK) and 50% 200 m flint for YEARS in gas kilns....... and it does not get "glassy".

 

With a chemical analysis like this......... even with the repeated heatwork of multiple firings........... not going to melt to a glass.

 

Silica...................... 50.00
EP Kaolin................... 50.00
=========
100.00

Take the shelves to the local place that is likely associated with an auto repair facility........ that does sandblasting.  If the shelves are clay type.... tell them to take down the surface until it is all just beige.  If they are silicon carbide, tell them to take it down until it is sort of black.  And so on.  Won;t be very expensive, that is the tool for the job, and they can handle the toxic dusts.

 

I HAVE seen people make the mistake repeatedly of using an unlabeled bucket of "white stuff" that they thought was kiln wash.... and glaze their shelves! 

 

 

best,

 

.........................john

[Guest JBaymore]

I guess my experience in my own studios and the student-filled studios where I have taught at MassArt, Boston University, and New Hampshire Institute of Art have failed to teach me anything about novice type screw-ups and the nature of various glazes and other stuff people put into kilns.  Sorry.

 

best,

 

..........................john

[Norm Stuart]

Your skill-set and presence as a teacher probably heads off a lot of potential problems before they end up in the kiln.

 

I'm only infrequently at our studio and I rarely load our kiln, so have procedures and material selection set in place to try to minimize the effects of our inevitable worst case scenarios.

 

I teach ceramic chemistry to those who are interested when I'm there, but the primary model in our studio tends to be learning by doing. 

 

Even with occasional incidents, I think this is a better learning environment for people than our studio's previous model where two experts did everything and no one else at the studio was allowed to learn how to fire a kiln, make a glaze, or participate any number of other things.  Maybe I'm just lazy - being unpaid can lead to that sort of perspective.

 

Three weeks ago may partner ran over and stopped a kiln fire during the pre-heat because in talking with me he realized that the person he had loaded the kiln with had applied a bottle of polymethacrylate plastic and water as "kiln wash".  It was on the same shelf as the kiln wash, but was clearly labeled polymethacrylate.  You'd never believe what goes on at our studio.

 

I guess my experience in my own studios and the student-filled studios where I have taught at MassArt, Boston University, and New Hampshire Institute of Art have failed to teach me anything about novice type screw-ups and the nature of various glazes and other stuff people put into kilns.  Sorry.

 

best,

 

..........................john

[Pres]

Off subject, and definitely demonstrating my own stupidity, but I had a container of white slip, and a container of kiln wash-both the same shape and size with different lids. Today these are labeled. 3 weeks ago they were not labeled and I was throwing patens and used the kiln wash on the wet clay as slip!  Metal ribs can work wonders when you have a problem like that, as it was when getting ready to trim that I realized my mistake.

[Norm Stuart]

We're human so mistakes are inevitable. 

 

I think my primary mission is to prevent the backyard behind my Optometrist's office, our ceramic studio, from becoming an EPA Superfund site.

 

Off subject, and definitely demonstrating my own stupidity, but I had a container of white slip, and a container of kiln wash-both the same shape and size with different lids. Today these are labeled. 3 weeks ago they were not labeled and I was throwing patens and used the kiln wash on the wet clay as slip!  Metal ribs can work wonders when you have a problem like that, as it was when getting ready to trim that I realized my mistake.

[neilestrick]

I'm with John on this one. But we've had that discussion before.

[Pres]

I try to be environmentally friendly by avoiding materials that are harmful to me, therefore the environment. At the same time, if having a sandblast job or commercial grind of a set of shelves save me the inhaled dust, and dust/girt around the studio and house, I'm all for it.   Some things are definitely worth paying for.

[Guest JBaymore]

Off subject, and definitely demonstrating my own stupidity, but I had a container of white slip, and a container of kiln wash-both the same shape and size with different lids. Today these are labeled. 3 weeks ago they were not labeled and I was throwing patens and used the kiln wash on the wet clay as slip!  Metal ribs can work wonders when you have a problem like that, as it was when getting ready to trim that I realized my mistake.

 

 

I've NEVER done anything like that!   

[Norm Stuart]

Avoiding harmful materials would be terrific.

 

Unfortunately everyone involved in ceramics use many materials which are harmful to people.

 

So we have to settle for using potentially harmful materials in a safe manner.

 

At the top of the list there's silica and high silica materials, followed by most heavy metal colorant oxides/carbonates.  Cobalt, chrome, copper, nickel, manganese and exotic metals - all toxic.

 

We have respirators for dust or organic solvents - and washing / settling tanks to capture the heavy metals.  I'm impressed to see everyone jump up out of their chairs to intervene when a new person decides to wash out their brush or container with the hose into the garden "because they don't want to put their hands into the dirty water" in the settling tank.

 

Most glazes at our studio are safe once fired, but are poisonous to drink - and most recipes are made with ingredients which are more dangerous to breath when you're are measuring them out and mixing them, than if you drank them as a liquid glaze.

 

I try to be environmentally friendly by avoiding materials that are harmful to me, therefore the environment. At the same time, if having a sandblast job or commercial grind of a set of shelves save me the inhaled dust, and dust/girt around the studio and house, I'm all for it.   Some things are definitely worth paying for.

[Rebekah Krieger]

 

 

 

Take the shelves to the local place that is likely associated with an auto repair facility........ that does sandblasting.  If the shelves are clay type.... tell them to take down the surface until it is all just beige.  If they are silicon carbide, tell them to take it down until it is sort of black.  And so on.  Won;t be very expensive, that is the tool for the job, and they can handle the toxic dusts.

 

I HAVE seen people make the mistake repeatedly of using an unlabeled bucket of "white stuff" that they thought was kiln wash.... and glaze their shelves! 

 

 

best,

 

.........................john

Thanks! I never thought about having my husband sand blast them - he has that machine at work. He said he is going to try one for me and if it doesn't work I will just buy all new shelves.