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Fredrin

In Search Of A Great Transparent Glaze

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Hello all,

 

This is my first post here, though I have been stalking these forums for a while!

 

To briefly introduce myself, I have recently started out as a studio potter in Walthamstow, East London (home to William Morris and birthplace of the Arts and Crafts movement way back when).

 

I studied ceramics from 13-18, developing a love for the smoke and drama of Raku and rediscovered the joy of clay just over a year ago - been an addict ever since  ;)

 

I'm lucky enough to work with a talented illustrator who puts underglaze designs on some of my porcelain and white stoneware pieces, but I have rather been letting the side down lately by covering her lovely drawings in a rather funky looking transparent (a pre-mix from the local supplier).

 

The effect I'm going for is a perfectly transparent with a very high gloss, but what I'm getting is a milky glaze with a bizarre crinkly textured surface that is neither matt nor shiny!

 

Here's what it looks like:

 

post-78878-0-82562400-1470825155_thumb.jpg

 

post-78878-0-97003600-1470825167_thumb.jpg

 

I've fired to cone 6,7 and 8 with varying thicknesses and keep getting similar results.

 

Please can you lovely people recommend a recipe that produces a high sheen and will really bring out an underglaze design on a porcelain/stoneware body.

 

Many thanks! :)

post-78878-0-82562400-1470825155_thumb.jpg

post-78878-0-97003600-1470825167_thumb.jpg

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Wayne Bates Clear cone 6 from PMI

F-4 Feldspar 35

Gerstley Borate 23

Whiting   8

Strontium   8

EPK   8

Flint 18

                                  100

OR USE THIS WITHOUT THE COLORANTS
Selsor Faux Celedon ^6 Oxidation

 

Whiting 18.5

Neph Syen 25.8

EPK 18.8

Silica 31.1

Gerstley B 4.6

98.8

Copper carb 0.3

Mason #6600 Black 0.02

Link

http://community.ceramicartsdaily.org/gallery/image/3541-cone-6-faux-celedon/

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My favourite ^6 clear for over underglazes on porcelain is this one https://digitalfire.com/4sight/recipes/low_expansion_glossy_clear_cone_6_45.html. The 3249 frit is ridiculously expensive but I've done a version of this glaze subbing other stuff for it if you want it. Never boron cloudy, super forgiving glaze. (spectrum underglazes)

 

(porcelain kids bowls)

post-747-0-19780000-1470862969_thumb.jpg

post-747-0-19780000-1470862969_thumb.jpg

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Thanks

 

I was about to ask if Matt Fiske's faux celadon (minus colourant) would be suitable. 

 

Is it important to give these glazes a long soak?

 

I dont think this will work well, Fiske's faux celadon has a beautiful bubble matrix I did a lot of testing with it. He personally likes the bubble matrix in it, as do I. If you put it on really thin though there isn't much of a bubble matrix happening, I think your better off with a real clear recipe. I just worked with that glaze for the better part of 3 months testing and changing it slowly. 

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recipe    GLOSSY CLEAR, NO ZINC  cone 6

 

Kona F4 (or minspar)               35

Gerst;ey Borate                        23

silica                                          18

barium carbonate                       8

whiting                                        8

EPK                                            8

 

this works very well on my clay.  who knows what it will do on yours.  i use it because it does not affect underglaze or slip colors under it.  very shiny clear.  i don't like barium so if anyone knows a perfect substitute for it, please tell me.

 

pic is of a soapdish i made with leftover strips of a cone 6 porcelain and my friend denise did the frog, her trademark.

post-2431-0-41000400-1470952032_thumb.jpg

post-2431-0-41000400-1470952032_thumb.jpg

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Did going hotter improve it at all? Looks under fired.

 

If you want to do a little bit of testing buy a feldspar, china clay, quartz(silica), frit and whiting. If you look at all these recipes that is what they are. Well they use gersbor~ to source boron but I think a frit will work better for clear.

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Thanks to all for the great advice.

 

I've had a word with the supplier and as High Bridge Potter suggests above, I will go to a higher temp (cone 8) and give it a 30 minute soak. Under-firing seems to be the main problem.

 

I'll try out some of the recipes above but as a shortcut until I've got one fully tweaked, I've bought some Amaco clear celadon

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