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In a spark plug in which a space between a center electrode at the top end side and a terminal electrode at a rear end side which are arranged to be opposite to each other in an axial hole of an insulator, the glass seal is effected at a temperature within the range of 500 to 1000.degree. C. and und

In a spark plug in which a space between a center electrode at the top end side and a terminal electrode at a rear end side which are arranged to be opposite to each other in an axial hole of an insulator, the glass seal is effected at a temperature within the range of 500 to 1000.degree. C. and under a condition where the concentration of oxygen is 4-12 vol %.

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1. A method for producing a spark plug, comprising the steps of:inserting a center electrode from an upper end of an insulator through an axial hole of the insulator; inserting a seal glass member through the axial hole on top of the center electrode; and inserting a terminal electrode through the a

1. A method for producing a spark plug, comprising the steps of:inserting a center electrode from an upper end of an insulator through an axial hole of the insulator; inserting a seal glass member through the axial hole on top of the center electrode; and inserting a terminal electrode through the axial hole on top of the seal glass member, wherein a space between the center electrode provided at a top end side and the terminal electrode provided at a rear end side is glass-sealed at a temperature of 500 to 1000.degree. C. at an oxygen concentration in the range of 4 to 12 vol % and the glass sealing is effected by glass having a softening point of not less than approximately 450.degree. C. at a temperature approximately 50 to 150.degree. C. higher than the softening point.