From: Phil Hamling [pdah@optonline.net]
Sent: Sunday, April 22, 2012 12:10 PM
To: 'Gordon Czop'
Subject: RE: Paper
This section. It seems he found not to need the 2 glaze approach. I will try the ones I've turned bold today.
With a few exceptions ground and crystal glazes were now fused in only one firing.
The crystal glaze was applied irregularly on top of the bisque fired vessel, which had been covered first by ground glaze (H) by dipping.
Along with these tests others were run in the laboratory of the Bunzlau Ceramic School, with remarkable results as well.
In one test the following frit was used:
0.367 PbO
c)0.257 CaO . 0.300 Al2O3 . 3.570 SiO2
0.179 K2O 0.326 B2O3
0.163 Na2O
0.043 MgO
And a ground glaze with this formula
0.2 MgO
J) 0.3 CaO . 0.6 Al2O3 . 5.0 SiO2
0.5 K2O
and batches weight recipes:
c)
99.52
Feldspar
31.22
Zettlitz Kaolin raw
135.24
Sand from Hohenbocka
62.27
Borax, crystallized
83.77
Red Lead
25.70
Marble Dust
2.86
Magnesite
__________________
440.58
parts by weight
d)
278.00 Feldspar
25.80 Zettlitz Kaolin raw
108.00 Sand from Hohenbocka
30.00 Marble Dust
16.80 Magnesite
__________________
458.60 parts by weight
From a large number of experiments only the best will be mentioned. They differ from those previously given in their content of molybdic acid, iron oxide, titanium dioxide and the oxides of copper and manganese.
This on the whole was an improvement.
Now vanadic acid was abandoned entirely. In each test the
uncolored ground glazes were completely covered with crystal glazes. It showed that those crystal
glazes containing iron oxide developed much better without a ground glaze,
whereas the other glazes required one.
The
following mixtures proved to be the best:
15.
Glaze
Frit C
100
Copper
Oxide
10
Molybdic
Acid (anhydrous) 2
Rutile
13
___________________________________
parts
by
weight
125
16.
Glaze
Frit C
100.0
Copper
Oxide
10.0
Molybdic
Acid (anhydrous) 2.0
Rutile
13.0
Iron
Oxide
3.5
parts
by
weight
128.5
17.
Glaze
Frit C
100.0
Copper
Oxide
10.0
Molybdic
Acid (anhydrous) 2.0
Rutile
13.0
Manganese
Oxide 4.0
parts
by
weight
129.0
18.
Glaze
Frit C
100.0
Copper
Oxide
10.0
Molybdic
Acid (anhydrous) 1.5
Iron
oxide
1.5
Rutile
13.0
Manganese
Oxide 4.0
parts
by
weight
127.5
The
addition of molybdic acid tended to develop starry crystals with a diameter of
20 to 30 mm. The crystals did not grow too large, what would have been
disadvantageous. The color of glaze 15 was a vibrant green, glazes 16 and 17
got more brownish, and glaze 18 a yellowish green.
Glaze
18 was the most beautiful one, with radially star shaped crystals that
sometimes showed a bluish fringe, and some test tiles also got the above
mentioned iridescent glow in reflected light.
The Seger formulas of these glazes for comparison:
15.
0.330 CuO 2.392 SiO2
0.246 PbO 0.218 B2O3
0.172 CaO . 0.201 Al2O3 . 0.427 TiO2
0.120 KaO 0.036 MoO3
0.109 Na2O
0.023 MgO
16.
0.330 CuO 2.392 SiO2
0.246 PbO 0.218 B2O3
0.172 CaO . 0.201 Al2O3 . 0.427 TiO2
0.120 KaO 0.057 Fe2O3 0.036 MoO3
0.109 Na2O
0.023 MgO
17.
0.330 CuO 2.392 SiO2
0.246 PbO 0.218 B2O3
0.172 CaO . 0.201 Al2O3 . 0.427 TiO2
0.120 KaO 0.067 MnO3 0.036 MoO3
0.109 Na2O
0.023 MgO
18.
0.330 CuO 2.392 SiO2
0.246 PbO 0.218 B2O3
0.172 CaO . 0.201 Al2O3 . 0.427 TiO2
0.120 KaO 0.025 Fe2O3 0.036 MoO3
0.109 Na2O 0.025 MnO3
0.023 MgO
-----Original Message-----
From: Gordon Czop [mailto:gczop@hvc.rr.com]
Sent: Sunday, April 22, 2012 10:59 AM
To: Phil Hamling
Subject: Re: Paper
Phil:
Thanks , your highlighted section does not show. The point I see is that for the most part a ground glaze and crystal glaze are used. The crystal glaze and ground glaze are different viscosity . Powellite can be all over the kiln but it needs the right conditions, that is surface and temperature gradient, to condense and form crystals instead of frost or....... If the glaze is too fluid they cannot land a site.
Please advise which section you highlighted.
Gordon
>
> Gordon,
>
> Here it is. I have highlighted a section in yellow. I think this is
> what Ulrike was referring to and where to start.
>
> Phil
>