I thought it had long been established that Peter Parker built his original web shooters from spare parts and chemicals he found in his High Schools lab - or at least from having access to an advanced lab as an afternoon job.
According the the Marvel Database
“ Spider-Man's web-shooters are twin devices, worn on his wrists beneath the gauntlets of his costume, that can shoot thin strands of a special "web fluid" (the chemical composition of which is not known) at high pressure. (Note: The fluid itself is officially described as being pressurized at 300 psi, but the actual number has been known to change.) The spinneret mechanisms in each web-shooter are machined from stainless steel, except for the turbine component, which is machined out of a block of Teflon, and the two turbine bearings which are made of amber and artificial sapphire. The wristlets and web-fluid cartridges, the latter of which Spider-Man wears on his belt beneath his costume's tunic, are mainly nickel-plated annealed brass. The wristlets have sharp steel nipples, which pierce the bronze caps when the cartridges are tightly wedged into their positions.
The hand-wound solenoid-needle valve on each web-shooter is actuated by a palm switch; this in turn, is protected by a band of spring steel which requires a 65-pound pressure to trigger it. The switch is situated high on the palm to avoid most unwanted firings. An additional safety measure, to prevent misfires while Spider-Man is making a fist or carrying things, is that the trigger has to receive a double-tap from Spider-Man's middle and third fingers. The small battery compartment is protected by a rubber seal.
The effect of the very small turbine pump vanes is to compress (shear) the web fluid and then force it, under pressure, through the spinneret holes, which cold-draws it (stretches it: the process wherein nylon gains a four-fold increase in tensile strength), then extrudes it through the air where it solidifies. As the web fluid exits the spinneret holes, it is attracted to itself electrostatically, and thus can form complex shapes. The spinneret holes have three sets of adjustable, staggered openings around the turbine which permit a single, incredibly strong line; a more complex, spreading spray; and a thick, tremendously adhesive liquid.[6]
The web line's tensile strength has been estimated to be 120 pounds per square millimeter of cross section. The 300 p.s.i. pressure in each cartridge is sufficient to force a stream of the complex web pattern an estimated 60 feet. (It goes significantly farther if Spider-Man shoots it in a ballistic parabolic arc.)”
