How do theyy make spacesuits airtight?

Spacesuits are made of lots of different layers that each protect the astronaut from a different aspect of the outside environment. Only the innermost layer – known as the bladder – is airtight. It’s made of urethane- coated nylon that has machine-welded seams. The gloves are attached using airtight bearings that lock into place but still allow the hand to be rotated. These use precisely machined aluminium and titanium couplings with Teflon coatings for lubrication to prevent the metals cold-welding together in the vacuum of space. Astronauts also breathe pure oxygen so the suit can be inflated at less than a third of normal atmospheric pressure. Even so, spacesuits aren’t perfectly airtight. NASA allows the suits used on the ISS to leak up to 100ml of air per minute.

Astronauts breathe oxygen before and during a spacewalk to rid their bodies of nitrogen, which could form dangerous bubbles