Sparkly patches in glaze: how to achieve

[Nancy Krug]

In the 1950's and thereabouts some commercial floor and wall tile glazes were various pastels with small, closely spaced patches of sparkly, almost crystalline areas across the tile. The background glaze would be a satin/matte, while the sparkly patches would be glossy. The overall effect was like an irregularly spotted tile, where the shiny patches were slightly darker than the background color (probably just due to the difference in reflectivity).

I want to reproduce this look and have no idea how it was done. I am experimenting with lowfire glazes and glass frit, although I imagine originally it was done with some more basic chemical.

Any ideas would be very welcome.

[Ayjay]

This has to be a possibility.

http://digitalfire.com/4sight/material/mica_1018.html

[quote]Mica flake is used in low fire clay bodies to add a sparkle effect. [/quote]

[Ayjay]

For some reason I'm unable to edit my last post - it says there's 12 minutes left to do so.

The edit was nothing important but I'm unable to do it for some reason, I've signed out, cleared my cache and signed in again to no effect.

[George Lewter]

Trouble with the page, I can't edit it either. Give it a couple of days and try again. Database cleanup may take care of it.

[Ayjay]

OK, thanks George.

[Harold Roberts]

I use micro crystalline glazes which I suppose are the opposite effect you are looking for.

[George Lewter]

Jen's Juicy Fruit will create tiny sparkly crystals. I didn't get a great rendition of sparkles here, but this is JJF with iron, layered on top of Randys Red.

[Nancy Krug]

An update on my experiments with low fire "sparkly":

1.  I have tried many forms of mica in low fire glaze (versus the tile body, as suggested above). Some outcomes are promising.

   a.  Using an already glazed and fired tile, gum was brushed on and mica flakes dropped into the gum. The mica did fuse to the glaze underneath, making the overall surface rough. For small mica bits (almost powder), this was rather attractive. The larger the piece or flake, the less durable and less attractive.

   b.  Mica mixed into colored glaze and low fired was not good: the mica merely formed lumps covered by glaze.

2.  Glass frit (fine) sprinkled onto pre-glazed and fired tile (after gum applied) and refired resulted in speckles of color that were lumpy but not sparkly. This look can be attractive but didn't achieve the objective.