This article explains why ionoplast laminated glass can still bubble after a vacuum-bag pre-treatment. A bag removes bulk air, but it cannot make up for a weak autoclave vacuum circuit—pumps, valves, hoses, or ports that leak under heat and pressure. The other usual miss is a Stage-2 hold that is familiar from some PVB work but too cool for ionoplast to flow and wet the glass. The piece argues that both systems should be inspected first, and that a corrected cycle can often clear a defective but otherwise intact batch.