Glaze Interactions

[steiconi]

I've been handbuilding ceramics for years, and also do glass lampwork.  

I recently saw a picture ( http://cad-website-images.s3.amazonaws.com/wp-content/uploads/2015/11/17153323/MaterialsGlazes300T1.jpg  not my photo) that got me thinking about the similarities between glaze and glass.  

 

There are a lot of fun and fascinating techniques that rely on the chemical composition and/or physical attributes of different colors of glass. 

examples: 

--if you put a glass containing sulpher (usually in the ivory to golden tones) next to one containing copper (usually greens to blues), a fine dark line appears where they touch.  Does this happen with glazes, too?

 

--if you put dots of opaque glass onto a transparent bead, the opaque dots spread out until they almost touch, leaving a thin line of the transparent color separating them.  (If I were making a glass bead to look like the photo linked above, I would start with a dark blue transparent glass, put a ring of dots of opaque white on top, then cover the white with transparent turquoise, and add more rings of double dots.)  

 

Are there similar techniques in glaze?  

Do you have a favorite?  

 

Can anyone recommend a website to read more?  (Yes, I realize the photo is the cover of a book, but I don't want to spend $50, and my library doesn't have it)

 

I use low-fire glazes, would especially appreciate info on them.  

 

thanks!

 

 

 

[glazenerd]

The question you are posing is much more complicated than meets the eye. In the type of glass work you are doing: you are either slumping or fusing at maximum temperatures of 1475F. Either way, the glass never reaches a complete melt. Glass and glaze are both covalent bonds at the molecular level: the exception being crystalline glaze which is an ionic bond which only applies to the crystal itself: not the glassy matrix the crystal grows in. In glaze chemistry you are delving into eutectics: forming a glassy matrix from raw materials.

The only glaze that you can play with to create effects on any level would be crystalline glaze. There are commercial premix glazes that are designed to produce effects, but they are not the same chemistry as crystalline glaze. Crystalline glaze has to be highly fired to produce the fluidity required, not only for the glaze, but also a complete melt of the two primary ingredients used to form the crystals themselves. You can influence the crystal growth in relation to size, shapes, and total population on any given piece. You can also control the glaze flow to seem degree, but not completely. It is a highly complex glaze and  takes years to really master and control. Below is a crystalline tile that uses a combination of rare earth oxides and aluminum oxide to produce a special effect. In addition, a third layer of glaze modifier was used to create the illusion of matte and gloss.

 

 

Nerd

[MatthewV]

Pretty much any two glazes can be applied with an overlap. Then to some extent dependent on the glazes, they will interact. The most vivid example is pink (chrome-tin) glazes and dark (iron) glazes. The interaction becomes a light brown color. The chrome stops interacting with the tin and attaches to the iron is my best guess.

 

Some of the ingredients used are different and many will be the same. High quality paint pigments also use the same chemistry.

[steiconi]

thanks! gives me something to think about

[rayaldridge]

Some of the effects you seem to be talking about can be achieved using slip on leatherhard ware.  If you put two blobs of different-colored slip next to each other, one color can be pulled into the other with a quill or other pointy tool.   Look up English slipware, which has to be among the most magnificent ceramic creations of all time.