Bottom forming process

A process for the preparation of a glass container from a glass tube in a glass processing machine, the glass tube comprising a first portion with a first end, a second portion with a second end, and a longitudinal axis (Ltube) that passes through a center of the first end and the second end, the glass processing machine comprising a plurality of processing stations, a first clamping chuck and a second clamping chuck which are adapted and arranged to hold the glass tube while rotating the glass tube around its longitudinal axis Ltube and to transport the rotating glass tube from one glass container processing station to the next one, a heating device, and a mold matrix, the process comprising the steps of

• J) heating the glass tube at a defined position between the first portion and the second portion to a temperature above a glass transition temperature of the glass tube while the glass tube is rotating around its longitudinal axis Ltube and pulling apart the first portion and the second portion thereby separating the first portion from the second portion and forming a closed bottom at one end of the first portion;
• and
• II) moving the mold matrix towards the closed bottom and bringing the mold matrix into contact with the closed bottom, wherein, while bringing the mold matrix into contact with the closed bottom, a distance Ym between the mold matrix and the first clamping chuck is decreased stepwise, wherein the distance Ym between the mold matrix and the first clamping chuck in process step II) is decreased in a first step IIa) and a second step IIb), wherein the mold matrix is in contact with 50% or more and/or 90% or less of a surface area of the closed bottom during the first step IIa) and/or wherein the mold matrix is in contact with 65% or more and/or 100% or less of the surface area of the closed bottom during the second step IIb).