Naturally Occuring Glaze

[jrgpots]

Every morning I pass this volcanic outcropping on my way to work. It looks like a naturally occurring shino. It occurrs on about 1/2 of the rock faces. Does anyone know if this is a glaze. If so, could I grind it up and reglaze?

 

Any knowledge, experience, or ideas would be welcome.

 

Jed

[Guest JBaymore]

Not a great photo... but looks like a vein of feldspar. If so...... yes...... and will almost be a glaze at cone 10.

 

best,

 

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

[jrgpots]

It's hard to tell of the scale, but the area in the picture is 12 ft tall and 4-5 ft wide. It is only on the surface, being 1/2 inch thick.

 

I'll get a better picture.

 

Jed

[Tyler Miller]

It can't hurt to make a few test tiles and see how it works.  Maybe one as is, then maybe a few substituting it as a feldspar in a few of your favourite shino recipes?  Using natural materials like this really excites me.

[jrgpots]

Local geologist says it is calcite with added iron and magnesium.....kind of an iron laden dolamite.

 

Jed

[Guest JBaymore]

Now find a seam of quartz.  And some local clay.  Do a triaxial with the dolomitic rock, the quartz (silica), and the clay .... and you'll have some glazes to work with.

 

best,

 

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

[jrgpots]

I have a beatiful butter cream colored, plastic cone 10, locally dug clay I found slaking right now. A local mine has quartz. I have a chocolate colored benonite/keolinite that melts at cone 5-6. I have granite dust and grit as well. And I have tumbleweed ash which is about 80% silica.

 

I plan on

1. A triaxial blend of tumbleweed ash, dolamitic rock, and local butter cream clay.

2. A triaxial blend of granite dust, tumbleweed ash, and butter cream clay.

3. Replace tumbleweed ash with local quarts in above blends.

 

By next week about 50 lbs of the local clay will be ready to throw. I'll post pics. It's good looking clay.

[Guest JBaymore]

I'm excited to see what you get.

 

best,

 

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

[Bob Coyle]

I can understand mining your own clay and feldspar, but any kind of pure quartz from your mine is going to be pretty much the same as the silica or flint you buy and far less trouble.

[Guest JBaymore]

I can understand mining your own clay and feldspar, but any kind of pure quartz from your mine is going to be pretty much the same as the silica or flint you buy and far less trouble.

 

Nope.  While when a glass goes to full melt and has time to "fine out" the final fired chemistry can be predicted by the chemistry software..... there is also some aspects of the raw materials sourcing that impacts the visual appearance of the glaze relative to the firing cycle.

 

Example...... let's say a glaze recipe calls for 100 grams of flint in a 1000 gram batch.  If I put that 100 grams into the batch as 325 mesh milled powder.... I get one kind of fired effect if I stop the firing at cone 9 down over a 10 hour up cycle.  But if I put that 100 ggrams into the batch as tweo 50 gram chunks........ well.... you can guess how much the var ious fluxes in the rest of the glase will have been able to react with the flint in the interior of the 50 gram chunks.

 

So if the local quarts is hand crushed, not wet milled and otherwise beneficiated, the packing of the particles in the glaze coating on the piece weill be very different than using commercial materials.  As will the physical geometry of the quartz particles....which also will impact how the otehr ingredients react with the quartz in the sintering and then melting glaze.

 

THIS is the secret to actual Japanese shinos.  It is the preparation of the rock that forms the glaze (either 100 percent of the glaze or down to about 90 percent of the glaze).

 

best,

 

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

[Bob Coyle]

Right John... if you are talking about mesh size, not chemistry. I hand ground some volcanic ash in a mortar and pestle and got very different results than with the 300 mesh commercial.

[Guest JBaymore]

Right John... if you are talking about mesh size, not chemistry. I hand ground some volcanic ash in a mortar and pestle and got very different results than with the 300 mesh commercial.

 

Yup... that is what I am talking about.  But not only "mesh size".... but geometry of the particles.

 

If particles have sharp edges.... they begin to sinter at those fine edges eariler than they would if the partiicle was more of a cube or round object. This changes how they interact with surrounding particles.

 

Particle size matters in the melting process...... this is why some glazes are intended to be ball milled. The finer they are, the more intimate the mixture ion the dry glaze coating....and that changes the WAY the glaze melts. If the glaze is never allowed to finally fine out before the cooling cycle starts....... the genesis of the melting process is very evident in the viusal results.

 

*This also can screw up the predicted glaze chemistry done by calculations.... because the glaze is NOT fully melted and the chemistry has not reached the final equilibrium state. Same with glazes the percipitate crystaline material upon slow cooling.

 

best,

 

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

[jrgpots]

The geometry and particle size aside,  I get a sense of connection with my "home" when I take local materials, prepare them (ball milling, crushing, etc.) and arrive at a "new to me" glaze. 

 

I know there are cheaper ways, more practice ways, etc.  However, this is a road less traeled.  As Robert Frost has written about "two roads diverrged in the wood, and I, I took the one less traveled by, And that has mde all the difference." 

 

Bob, I'm just endulging my whim for "local grown" stuff, especially if I have hunted it, collected it, and prepared it.

 

Jed 

[RuthB]

You might be interested to see the work Matthew Blakely of the UK. He is collecting and preparing local materials from all over the UK in 

just this way with some beautiful and compelling results. Also, Judith Duff in NC studied Japanese Shinos, applied what she learned to

NC feldspars. She has developed a North Carolina shino from minimally processed local feldspar. It will be great to see your results, as well.

 

Ruth

[Bob Coyle]

 

Bob, I'm just endulging my whim for "local grown" stuff, especially if I have hunted it, collected it, and prepared it.

 

Jed

If it's fun and semi-legal do it.   I have been eying a clay deposit that  has... well sort of ...been "community property" for years. There is also a lapidolite mine near here that is open for prospecting with permission. I mined some of this a couple of years ago and used it in a glaze but got nothing out of the ordinary. I don't have a ball or hammer mill so its the sledge and burlap bag and then hand grinding in a mortar & pestle... not much 300 mesh produced.

[DarrellVanDrooly]

If it is calcite then id do some tests with additions of a flux and dolomitic rock. Maybe even cobalt as a colorant?

 

Darrel

[RuthB]

I know that Matthew Blakely and Judith Duff had to get permission from various agencies to collect the materials that went into wild glazes

they made.

 

Ruth

 

 

 

Bob, I'm just endulging my whim for "local grown" stuff, especially if I have hunted it, collected it, and prepared it.

 

Jed

If it's fun and semi-legal do it.   I have been eying a clay deposit that  has... well sort of ...been "community property" for years. There is also a lapidolite mine near here that is open for prospecting with permission. I mined some of this a couple of years ago and used it in a glaze but got nothing out of the ordinary. I don't have a ball or hammer mill so its the sledge and burlap bag and then hand grinding in a mortar & pestle... not much 300 mesh produced.