

What gave the idea to make the Golden Gate Bridge red/orange? - Clara

The orange vermillion, often called "international orange," was chosen by architect Irving Morrow. He chose it because the warm color would pair well with the landscape nearby and serve as a complementary color to the cool colors of the sky and sea. The orange also helps with visibility for passing ships.

Are the zipper machines for the Golden Gate Bridge faster than the old way? What's the etiquette of driving around those machines? Why do they have two machines? And why or what dictates when the barrier gets moved? - Stephanie

OK, so this one is cheating a little bit. We already answered this question in a full episode and story in 2017. You should really click through for the full answer, but if you're pressed for time, the short version is:

It's not actually faster. Both the zipper and the old way took about an hour.

"Just act normal" and drive right past the machine if you come upon it in traffic.

There are two machines so they can change the number of lanes quickly and efficiently.

Morning rush hour = four lanes into the city, evening rush hour (except on Monday) = four lanes out of the city.

How many times has the Golden Gate Bridge been painted? - Jason

The bridge was painted when it was originally built and received only touch-ups until 1965, when corrosion meant the original paint made of a red lead paste and a linseed carrier had to be removed. It was replaced over many years with an inorganic zinc silicate primer and acrylic emulsion topcoat. Then in 1980, that paint was replaced with a zinc primer and acrylic topcoat. The bridge now continually receives touch-ups, but the whole bridge has been entirely repainted only a few times.

Has anyone ever swam under the Golden Gate Bridge from Presidio to Marin?

Yes! We’re going to turn this one over to Denise Sauerteig, one of our colleagues with KQED Education, who is a member of the Dolphin Club, a historic swimming and rowing club in San Francisco that was established in 1877 and hosts an annual swim under the bridge:

“This is my favorite swim and the Dolphin Club has been doing it for over 100 years, well before the bridge was even built. We take a boat out to just outside the gate on the San Francisco side of the bridge. We jump off the boat and then swim the length of the bridge until we reach the north side just inside the gate. Then we jump back on the boat and celebrate with Irish coffees and doughnuts. No wetsuits, just a bunch of wild open-water swimmers enjoying the view of the underside of this great architectural structure. The current sweeps you along in an S-curve, and sometimes the water is choppy and feels like you're in a popcorn machine, but there's nothing like floating on your back and taking in a view that very few people ever really get to enjoy! It's a short swim but one of the most memorable possible in the San Francisco Bay.”

My mother was living when the Golden Gate Bridge was built. She would say the builders included a steel mesh under the water so no submarines could pass under. I often wondered is this true. - Donna

Donna's mom is pretty close.

During World War II, San Francisco Bay was fortified in a number of ways. Huge guns were positioned around the coast to take down enemy forces. The next line of defense: three minefields with more than 600 underwater mines sitting outside the Golden Gate.

If enemy submarines made it past the guns and through the minefields, they would be stopped by anti-submarine netting inside the Golden Gate.

According to the Seacoast Fortifications Historic Resource Study, the net extended from around Yellow Bluff (south of Sausalito) to the eastern end of the Presidio. Tugboats were used to open and close the net for friendly ships to pass.

So there was a net nearby, but it was not attached to the bridge.

I've noticed that the towers of the Golden Gate Bridge are over the water. Presumably, the bases of these towers are anchored to the bay floor. I was wondering how it was possible to anchor the towers to the bay floor, especially in the 1930s. Did they lay underwater concrete? - Jared

The north tower stands just off the shore of Marin, but the south tower stands in the middle of Golden Gate Straits and presented a huge engineering challenge.

To clear the area where the base would sit, divers were sent down 110 feet below the water. They set off dynamite charges and used high-pressure hoses to remove loose material.

Before placing the tower, workers built a barrier that would protect the tower from oncoming collisions. The barrier was made by sending concrete through funnels into wooden forms that were set in place by divers. Once the barrier was above water, workers called it a "giant bathtub."

Next they filled the bottom portion of the barrier with concrete to serve as the foundation of the tower. The remaining 9.4 million gallons of seawater were pumped out of the giant “bathtub,” and workers reinforced the structure with more concrete and steel.

From there, the steel tower was assembled inside the barrier.

We're not the only ones who love the Golden Gate Bridge. Here are a few other links to check out to satisfy your bridge curiosities: