Abstract This patent application describes a composition for glazing ceramic ware, preparations useful for making same, process for glazing bodies and substrates with same, and resulting coated ceramic bodies. The composition for glazing is characterized by containing a particulate vitrifiable material, at least a substantial fraction of which is in the particulate vitreous state said vitrifiable material, after melting into a fluent vitreous state, being self-nucleating or autocrystallizable or crystallizable, into a substantially dimensionally stable continuous vitreous film in which are dispersed crystals of low thermal expansion. The glazing composition is particularly suited for glazing low expansion ceramic whiteware. Set forth as useful preparations are special particulate alkaline earth aluminosilicates modified with flux in proportion controlled to restrict the development of a primary low thermal expansion crystalline phase, some of said preparations being modified with zirconia. The glazing process comprises partially coating a ceramic body with the composition for glazing, firing the coated body at a temperature sufficiently high and for a time sufficiently long for converting the composition into a fluent continuous vitreous surface coating, then adjusting the temperature to a value at which crystal growth in the surface coating occurs at a measurable rate, and finally cooling the resultant glazed ware at a rate consistent with keeping the ware integral. The invention shows particular advantage for making glazes of adjustable and low thermal expansion for thermal shock and mechanical shock resistant ceramic whiteware, for example, dinnerware, cookware, ceramic tile, acoustical tiles of the mineral type, sanitary ware, artware, and electrical and technical porcelain. The invention is specially adaptable to conventional ''''two-fire'''' glazing practice.
IN A PROCESS FOR FORMING A SUBSTANTIALLY NON-POROUS, SEMICRYSTALLINE GLASS CERAMIC GLAZE ON A FIRED CERAMIC BODY BY TGE "TWO-FIRE" PROCESS, SAID GLAZE HAVING A COEFFICIENT OF THERMAL EXPANSION OF LESS THAN 5 X 10**-6/*C, THE IMPROVEMENT COMPRISING THE STEPS OF: A. AT LEAST PARTIALLY COATING SAID BODY WITH A GLAZE PREPARATION COMPRISING CERAMIC FRIT CONSISTING ESSENTIALLY OF:
Claim 2
Dependent Claim
58 words
IN A PROCESS FOR FORMING A SUBSTANTIALLY NON-POROUS, SEMICRYSTALLINE GLASS CERAMIC GLAZE ON A FIRED CERAMIC BODY BY TGE "TWO-FIRE" PROCESS, SAID GLAZE HAVING A COEFFICIENT OF THERMAL EXPANSION OF LESS THAN 5 X 10**-6/*C, THE IMPROVEMENT COMPRISING THE STEPS OF: A. AT LEAST PARTIALLY COATING SAID BODY WITH A GLAZE PREPARATION COMPRISING CERAMIC FRIT CONSISTING ESSENTIALLY OF:
Claim 3
Dependent Claim
94 words
The process of claim 1 wherein: the firing is performed at a temperature not substantially more than about 500*C above the liquidus of said frit; the temperature adjustment thereafter is downward to a temperature below the liquidus of the highest melting crystal produced in the vitreous matrix of said surface coating, but not substantially more than about 300*C below the liquidus of the primary low expansion crystal phase formed by crystallization of said surface coating; and the cooling rate of the resultant glazed body is not substantially in excess of about 40*C per minute.
Claim 4
Dependent Claim
11 words
The process of claim 2 wherein said frit consists essentially of:
Claim 5
Dependent Claim
61 words
In a fired ceramic body having a fired glazed frit coating thereon, said body having been fired prior to the application of the glaze frit coating, said glazed frit coating comprising a low-expansion, non-porous, semi-crystalline glass ceramic glaze coating, said coating having a coefficient of expansion less than 5 X 10 6/*C, the improvement wherein said glazed frit consists essentially of:
Claim 6
Dependent Claim
61 words
In a fired ceramic body having a fired glazed frit coating thereon, said body having been fired prior to the application of the glaze frit coating, said glazed frit coating comprising a low-expansion, non-porous, semi-crystalline glass ceramic glaze coating, said coating having a coefficient of expansion less than 5 X 10 6/*C, the improvement wherein said glazed frit consists essentially of: