they cool as the metal mounting insert cools with the glass the two materials shrink back to their room temperature size the rate at which the material e g copper expands when heated and the rate at which glass expands when heated are nearly matched so when it cools back to room temperature they shrink at the same rate as well if the metal and glass did not expand and contract at the same rate the glass would shrink faster than the metal and burst apart or the metal would lose its bond to the glass and simply slide off if the coefficients of expansion match the glass and copper are bonded at a molecular level at any temperature as a result the cooling process is well controlled to avoid issues that may arise with the difference in the material 39 s expansion coefficients a further embodiment of the present invention comprises a method of manufacturing glass pieces using a glass blowing pipe 100 and the metal mounting insert 115 described above the method is described in the flowchart of fig5 in a first step 500 the metal mounting insert 115 is attached to the headstock section 112 of the glass pipe 100 in a second step 505 the metal mounting insert 115 is placed in the furnace and dipped directly into the crucible of molten glass the molten glass gathers directly onto the metal mounting insert 115 in a subsequent step 510 once a sufficient amount of molten glass has been gathered upon the metal mounting insert.