Partially devitrified porcelain composition and articles prepared with same

A porcelain coated circuit board having a metal core and having applied to the surface of the metal core a coating of a devitrified porcelain which is free to substantially free of alkaline metal oxide, said porcelain consisting essentially, on an oxide basis, of:

• (a) from about 6 to about 25 mole percent of barium oxide;
• (b) from about 30 to about 60 mole percent of MO wherein MO is a member selected from the group consisting of magnesium oxide and mixtures of magnesium oxide with at least one member selected from the group consisting of zinc oxide and calcium oxide;
• (c) from about 13 to about 35 mole percent of boron trioxide;
• and
• (d) from about 10 to about 25 mole percent of silicon dioxide;
• said coating having a deformation temperature of at least 700.degree. C. and said coating of porcelain having defined thereon an electrical circuit.