Porcelain paint
Porcelain paints are colors that are suitable for application and later firing on porcelain . Their manufacture and composition was and is still treated as a closely guarded secret by the porcelain manufacturers . For the hobby of porcelain painting, there are porcelain paints that do not have to be fired. You use water-based acrylic paint , which only needs to dry, or synthetic resin paint , which is hardened in the oven. These colors are not resistant to abrasion.
The colors
There are underglaze colors that have to withstand the firing process at approx. 1300 degrees and porcelain colors for painting on the glaze ( muffle colors ), which are fired at approx. 900 degrees. The pigments of the porcelain paints consist of metal oxides . Different colors can be formed from iron oxide pigments , depending on the oxidation level and starting material: red, yellow, sepia, brown, black and violet. Copper green is yellowish green. Chrome green , which only existed after 1811, is intense green. Gold as a color can be applied as dissolved gold salts. After firing, the gold surface is matt. Polishing with an agate pencil gave a shiny gold surface ( polished gold ). After 1817 it was a high-gloss gold surface (by the fire bright gold ) directly generate for you a lot less gold needed, but is less resistant to abrasion.
Manufacturing
The production of the porcelain colors is similar to the enamel production. The color pigments are melted into a special glass mass as a carrier material, which becomes sufficiently liquid at the intended firing temperature without flowing too much. The mass is ground into powder and provided with a binding agent (oils and turpentine ) so that the colors can be applied with a brush. The binding agent is burned off without residue during the firing process.
List of pigments
| Color designation | Metal oxide | formula |
|---|---|---|
| Ruby red | Lead chromate | PbCrO 4 |
| Gold purple | Gold / tin oxide | Au / SnO 2 |
| red | Iron oxide red | Fe 2 O 3 |
| red | Silver dichromate | Ag 2 Cr 2 O 7 |
| orange | Uranium (VI) oxide | UO 3 |
| yellow | Iron oxide yellow | FeO (OH) |
| Naples yellow | Lead antimonate | Pb (SbO 3 ) 2 or Pb 3 (SbO 4 ) 2 |
| Chrome yellow | Lead chromate | PbCrO 4 |
| Barite yellow | Barium chromate | BaCrO 4 |
| brown | Iron oxide brown | Mixture of iron oxide yellow, red and black |
| Yellow-green | Uranium (V, VI) oxide | U 3 O 8 |
| Copper green | Copper (II) oxide | CuO Cu 4 H 4 [(OH) 8 | Si 4 O 10 ] · n H 2 O |
| Chrome green | Chromium (III) oxide | Cr 2 O 3 |
| Smalte (cobalt blue glass) | Cobalt (II) oxide in glass | CoO in K 2 O-SiO 2 glass |
| Thénards cobalt blue | CoO · Al 2 O 3 | CoAl 2 O 4 (Co-Al spinel) |
| violet | Manganese (IV) oxide | MnO 2 |
| black | Iron oxide black | Fe 2 O 3 / FeO |
| black | Uranium (IV) oxide | UO 2 |
| black | Iridium (III) oxide | Ir 2 O 3 |
| black | Platinum (IV) oxide | PtO 2 |
Historical
The following are examples of historical porcelain paint recipes published in 1825 that show how porcelain paints were made:
Blue: 24 Loth white sand (SiO 2 ), 6 Loth Zaffer (a cobalt oxide mixture of CoO, Co 2 O 3 and As 2 O 3 ), 6 Loth red lead (Pb 3 O 4 ), pounded in a mortar, placed in a crucible , well cemented and, after drying, glowed in a lively fire for half an hour, then removed, pounded, put on 32 lots of which 28 lots of powdered saltpeter (KNO 3 ) were added, put back into the crucible and put on a very violent fire for 2 hours annealed.
Cobalt blue: 1 part Zaffer (cobalt oxide mixture), 3 parts sand (SiO 2 ), 1 part potash (K 2 CO 3 ). When melted, these ingredients produce a blue glass, which is called smalt, pushed, sifted and ground in special mills.
Green: Red lead (Pb 3 O 4 ) 1 pound, copper hammer blow (CuO) 1 pound, pebbles (SiO 2 ) 5 pounds. You make three equal parts out of it and add the same amount of saltpeter (KNO 3 ), bring the mixture into a melting pot, melt it over a strong fire, let it cool down, push it off and rub it off on a grating stone.
Red: pitch ( hydrocarbons, etc.) 8 solder, silver smoothness (Ag 2 O) 4 solder, red chalk (Fe 2 O 3 heavily contaminated with clay ) 2 solder. Powdered and mixed.
Purple: Red lead (Pb 3 O 4 ) 1 pound, brownstone (MnO 2 ) 1 pound, white pebbles (SiO 2 ) 5 pounds. Make three equal parts out of it, add as much saltpeter (KNO 3 ) as such a part makes up, calcine, melt and rub the mixture.
Gold purple by Andreas Cassius : You dissolve pure gold in aqua regia and add gold or acid until you get a saturated solution. The same acid is also used to make a saturated solution of tin and pour this into the goldsolution. A purple powder will fall, which will be collected andwashed outwith distilled water .
literature
- Heinrich Hirzel: Das Hauslexikon: Encyclopedia of practical life knowledge f. all stands. Volume 2, 3rd edition, Breitkopf & Härtel, Leipzig 1859, p. 690.
Individual evidence
- ↑ Colin Mackenzie, Heinrich Ferdinand Eisenbach: Five thousand new English recipes for all incidents in life, or new complete house library . Second part. JB Metzler'sche Buchhandlung, Stuttgart 1825, glass and porcelain painting, p. 287–290 ( p. 287 of the copy of the Bayerische Staatsbibliothek online in the Google book search).