Part 3

You'll start by facing a large white wall. Turn to your left and aim at the top of this wall, which is on the far right of the room. You'll want to use your portals here to guide blobs of gel over the turrets. Taking them out a couple at a time is the way to go. Once that's done, place a portal on the very bottom right-hand corner of that wall. Then, fire another portal near your feet.

Step out onto the metal railing that's now below you and carefully walk across to where the turrets used to be. You'll then want to use the blue gel to bounce yourself back over to the walkway. From there, head upstairs towards the office area.

Next, you'll need to aim through some broken glass. Place your portal directly underneath the tube that transports the bombs. After that, place a portal directly above the switch and press the button. The bombs will then fly through your portals and smash open the white Conversion Gel pipe, which is your ticket to escaping to the portal outside.

Once you reach the room with the conveyor belt, make a run for the orange pipe. This will automatically switch on the conveyor belt. Now, quickly run up to the platform on your right. Plant a portal on the wall that's directly opposite the orange gel pipe. From there, look to your right and set a portal under the glass pipe. Press the button again. The bomb will drop onto the orange gel pipe, breaking it and coating the conveyor belt in gel.