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TEOMCROTE = TEOTWAWKI on steroids! The End Of Mankind's Current Reign Over The Earth takes into account that our ancestors were neither suicidal, stupid, nor our genetic inferiors but still wound up getting wiped off the Earth. Whereas CSER [cser.org: Centre for Study of Existential Risk] tries to PREVENT this dispensation from coming to an end, TEOMCROTE works from the eventuality/possibility/probability that the end our age takes place and what to do then

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pottery


clay
glazes
equipment
etc.

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6/22/2011, 2:38 pm Link to this post Send Email to TheLivingShadow   Send PM to TheLivingShadow Blog
 
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glaze recipes


]mid range glaze recipes

]What goes into glazes [[sign in to see URL]]

Feldspar is used in varying proportions in porcelain, china and earthenware. Earthenware contains on an average

12% feldspar
25% ball clay
28% china-clay
35% quartz
This proportion of feldspar varies in different products like

Wall tile -5%
Floor tile -30%
Statutory porcelain -50%
Sanitary china and prodelain bodies -30%

In ceramic bodies, potash feldspar is preferred although soda feldspar works as a good flux and can be satisfactorily used in developing ceramic bodies.

In the preparation of glazes the fine powder of feldspar is mixed with silica powder and a thin slurry is made. The fired up goods are dipped into the slurry and fired again. This imparts glaze to the surface. Some other ingredients are also added to the slurry to impart glaze and lustre. Each pottery factory has its own technique of preparing slurry which is regarded as a trade secret.

Glazes high in feldspar (35% or more) are plagued by crazing problems, yet still used by tens of thousands of potters. 'Flux saturated' glazes with more than 50% feldspar may be unbalanced and lack adequate glass former or alumina to create a stable hard glass resistant to leaching.

Last edited by TheLivingShadow, 6/23/2011, 2:27 pm


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glaze sources


]Very large site.

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10/25/2011, 11:25 am Link to this post Send Email to TheLivingShadow   Send PM to TheLivingShadow Blog
 
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what's in a glaze


Glazes need a balance of the 3 main ingredients: Silica, Alumina and Flux.
* Too much flux causes a glaze to run, and tends to create variable texture on the surface. The texture may vary from shiny, where the glass is balanced, to matt where the excessive flux oxides may form visible, possibly lumpy, crystals.
* Too much silica will create a stiff, white and densely opaque glass with an uneven surface. It will be glossy in spots, but the suspended silica can form crystals producing harsh dry surfaces. Too much silica will also inhibit the melting of a glaze, and the resulting surface will be roughly textured like sandpaper.
* Too much alumina causes a glaze to stiffen and tend towards opacity, again with a textured surface where it is dry in spots. Glazes will often have pinhole defects. Too much alumina can inhibit the melting of the glaze to the extent that a poor quality matt glaze results, one that looks matt but is prone to discoloration.

To provide flux in the glaze, we need a material that contains one or more of the following:
Li2O=Lithium Oxide, comes from Lithium carbonate, Petalite, Spudomene
K2O=Potassium Oxide; comes from Potash Feldspar, frit
CaO=Calcium Oxide, comes from whiting, limestone, wollastonite (also provides SiO2), wood ash, bone ash, dolomite (also provides MgO)
MgO=Magnesium Oxide, comes from magnesium carbonate, dolomite (also provides CaO), talc
ZnO=Zinc Oxide, comes from zinc oxide
SrO=Strontium Oxide, comes from strontium carbonate
BaO=Barium Oxide, comes from barium carbonate
PbO=Lead Oxide (not used much due to toxicity)
Na2O=Sodium Oxide, comes from feldspar, FRIT, cryolite, nepheline syenite
TiO2=Titanium Dioxide, comes from pure titania, rutile
ZrO2=Zirconium Dioxide, comes from zirconium dioxide, zircopax, zirconium silicate
SnO2=Tin Oxide, comes from stannic oxide (SnO2 white), stannous oxide (SnO black)
B2O3=Boric Acid or Boron, comes from Colmanite, Gerstley Borate, CadyCal. Effective for lowering the melting point of a glaze.
If you've worked with glaze recipes at all, you probably recognize many of these terms, and can start to understand what they are used for.
Once you have the chemical composition of the ingredient, you can see what it contributes to the glaze. For example, is it primarily contributing silica, alumina, or a flux? Often a single ingredient contributes a combination of these. For example, Feldspar is primarily a combination of alumina and silica. And so is clay.

You may have heard of something called a unity formula, or Seger formula. This is a way of expressing a glaze by the ratios of its oxides rather than % of raw materials. It is one of the primary methods used in analyzing glazes. I'm going to skip the detailed math. But the concept is that using information about each raw material, you create a ratio of the amount of flux to the amount of silica and alumina. These ratios can then be compared to ones which have been determined to work in a certain way at a specific temperature.
These calculations are very detailed and take a long time to do by hand. And because there are many factors that all interact, it would take a long time to learn each material and the effect it has on a glaze. So potters have created a variety of computer programs that simplify the analysis and formulation of glazes.
You can learn more by taking the self paced on-line tutorial called Glaze Teach. GlazeTeachThe writers of this tutorial offer a glaze calculation software program called Matrix.
Digitalfire, a website that explains glaze chemistry and sells a software program called Insight to help automate this glaze analysis process.


]source

Last edited by TheLivingShadow, 10/25/2011, 11:34 am


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10/25/2011, 11:26 am Link to this post Send Email to TheLivingShadow   Send PM to TheLivingShadow Blog
 
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salt glazes


~trdavids/[sign in to see URL]]Salt-Glazed Ceramics
Salt can be used as a glaze. One can never use it in a kiln that's used for other things or other glazes, because the salt evaporates and settles on the sides of the kiln and will evaporate again.
Salt glazes can be used for food and liquid containing items. It's unpopular in modern glazing because it often leaves a mottled finish, because an oven needs to be reserved for salt glazes, because of toxic fumes it creates, and because the end product is unpredictable.
On the other hand, if you don't know how to make a glaze, throwing in some salt is easy. Salt's easy to come by, as well.

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10/21/2012, 11:29 am Link to this post Send Email to TheLivingShadow   Send PM to TheLivingShadow Blog
 


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