Precious metals preparations for the decoration of tiles

Bright Precious Metal Preparations are varnish-like organic compounds containing precious metals, combined with flux components (based on organic metal compounds) as adhesion promoters.
These preparations also contain resin solutions as film formers. On a smooth surface, a high-gloss precious metal film forms after firing. According to the color shade of the fired product, a differentiation is made between:

• Bright Gold, which develops a typical reddish-yellow gold shade after firing and contains a small proportion of silver;
• Bright Lemon Gold, which fires to a lemon-yellow shade, achieved by formation of a gold/silver alloy;
• Bright Platinum and Bright Palladium, which fire to a white-gold shade, achieved by formation of an Au/Pt or Au/Pd alloy.

Application

Ferro's Bright PM Preparations are generally supplied ready to use. If desired, suitable thinning oils can be added to adjust the viscosity. For spray application or for screen-cleaning, rapidly evaporating oils and solvents are required, whereas for the application of brush preparations, semi-fat oils are required.

For application by stamping, fat oils are the most suitable, because they have been specially developed to suit the composition of Ferro's Bright Precious Metal Preparations.

Consistency

Different consistencies are required depending on the application technique selected, as well as on the type of body to be decorated, in order to obtain optimal processing and firing characteristics. Preparations to be applied by brush, and hand-stamping require a low viscosity (40-500 mPas), while those processed by screen-printing or other mechanical application methods require a high viscosity (2.000-8.000 mPas).

Processing

Firing conditions depend on the type of body to be decorated. As the organic compounds in the preparation decompose during firing, good ventilation in the kiln (surplus oxygen in the kiln atmosphere) must be assured during the entire firing process, at least up to 500° C. In contrast to normal firing, fast firing in continuous kilns allows a reduction in firing time with a simultaneous increase in maximum temperature. Fast firing conditions impose special requirements on the preparations.

Table 1: firing condotions common in the ceramic industry

Material	Temperature ºC	Firing cycle
tiles	750-900	30-45 min

Brush application

Code	PM%	Description
Platinum
GP - 318		bright platinum
GP - 350		platinum standard
Palladium
GP 244/D		palladium
Gold
PM - 9947	9	gold
GG - 301/10	10	gold
Copper
PM - 9094		copper
Medium
DH - 26		medium

Screen printing application

Code	PM%	Description
Platinum
PM 12506		bright platinum
PM 12506		bright platinum standard
PM 5871		lustre platinum
Palladium
GP 5550		palladium
Gold
PM 5807	10	gold lemon yellow
PM 9090	8	lemon
PM 1001	10	gold reddish
Copper
PM 5889		copper
Medium
PM 0002		medium

Table 2: recommended meshes for screen printing PM Preparations

PM Preparation	Screen - Polyester (threads/cm2)
bright gold	120 - 150 S
bright lemond gold	120 - 150 S
bright platinum	120 - 150 S
bright palladium	120 - 150 S

Lustres

Lustres are varnish-like preparations, based on metal - and/or precious metals containing organic compounds, with resin solutions as film formers. When fired on porcelain, earthenware, enamel, tiles or glass they produce very thin, intensively coloured and lustrous layers, which give them their metallic iridescent finish. Lustres can contain up to 6% gold as well as silver, platinum and palladium. The Ferro product range contains both precious metal lustres and lustres without precious metals.

Consistency

PM preparations processed by spray gun, brush, and hand-stamping require a low viscosity (40-200 mPas).

Preparations processed by screen-printing or other mechanical application methods require a high viscosity (2.000-20.000 mPas).

Processing

Firing conditions depend on the type of body to be decorated.
As the organic compounds in the preparation decompose during firing, good ventilation in the kiln (surplus oxygen in the kiln atmosphere) must be assured during the entire firing process, at least up to 500° C.
In contrast to normal firing, fast firing in continuous kilns allows a reduction in firing time with a simultaneous increase in maximum temperature. Fast firing conditions impose special requirements on the preparations.

table 1: firing conditions common in the ceramic industry


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