Recycling Waste Glaze?

[oki 1]

I have a couple of buckets of unknown glaze materials.  When I test fired them I got a very dry underfired result.  Then I set about adding various materials,  looking for what would make it fusible, something like a glaze.  Testing systematically, I have added every material I have at hand and in combinations, such as, silica, feldspar, talc, whiting, gerstley borate, china clay, alumina, nepheline syenite, borax, rutile, and so on, at various quantities 10, 20 %. I can not get much of a change, and it has got me beat.  Surely something has to give.  Of course maybe if I added something at 50 to 100% I would get a change but this would be counter productive,  adding a lot of  material and just creating a double lot of some unknown recycled glaze, and  not making primary use of this quantity of waste unknown material. At that rate I might as well discard the waste glaze.  But to actually find a solution, adding something in the order of 10 or 20 %, does anyone have any insights? I am quite amazed that I have not found any addition that works. I have tested at cone 1, 3, and 6.  Of course it could be it needs a higher temperature, but that's not the point, because even a higher temperature glaze can be modified. The obvious additions just don't seem to be working. Let me put it this way. How can a mix of glaze material not be a glaze?  For materials which generally are a glaze, which ones when added together will not act like a glaze? A strange question? Any thoughts? 

[oldlady 2,806]

maybe it is a slip?

[Babs 1,206]

Well I can think of a number of "glaze" ingredients which would take a fair bit of additions to make it a glaze, think High Bridge has done extensive trialling of different ingredients and exactly what they do so read some of his posts.. Currie tests.

Chuck them if it doesn't look like Cornish stone, Albany , or any othe very expensive material.

It could in fact be BArium Carb, so don't play with too much gay abandon..

[High Bridge Pottery 685]

When is a glaze not a glaze? When it has glossed the plot 

 

Is it a bucket of glaze you have that is unknown or a single ingredient?

[Mark C. 4,867]

If it's alumina hydrate it will not flux very easy with additives.

Mark

[Chilly 901]

Are you firing it at the right cone?

 

I inherited an unlabeled bucket, tried firing it at: 

• ^06 - not a glaze
• ^6 - might be a glaze
• ^8 - is a glaze but still underfired.  

[curt 269]

You could take them to a laboratory and get them tested if there is really enough to be worth something.  XRD analysis or similar should give you a good idea of their chemistry. 

[Bob Coyle 116]

just try adding  5,10,15 20%  of Gerstley borate or frit 3134 0r frit 3125. If that doesn't flux it by cone 6, then you really have a problem. One of these should flux to shiny at cone 6 or well before.

 

Works for me.

[Babs 1,206]

could be kiln wash..

[Pieter Mostert 72]

There's an article on the digitalfire website that should help you narrow down the possibilities. The authors don't say what cone they fire their melt tests to, but I'd assume it's cone 6 or higher.

[MatthewV 259]

Even the more expensive white powders are hardly worth the time and uncertainty of testing...

 

Anyways, I would go through these steps:

1. mixing up a slurry and letting it dry to a normal clay working consistency. If it works like clay I would suspect ball clay or a kaolin. I might then add some to my clay slop.

 

2. fire a small ball from step 1. If it melted I would guess it to be a flux or frit; I might add some to a glaze slop every now and then.

As you mentioned, it doesn't melt. I would throw it out; even a full bag of most things is likely to not be worth the trouble.