Zim: The temperatures here in the northeast have dropped well below freezing. And someone suggested that it was time to go outside and photograph soap bubbles. If you have no idea what I'm talking about, Google frozen soap bubbles. When it's below freezing outside, blowing soap bubbles will cause delicate crystals to form across the surface of the bubble. Sometimes it looks like snowflakes, sometimes it looks like tiny little trees. You really don't know what you're going to get, and that's what makes this fun and challenging.
Zim: I've tried this a couple of different times, and I've been extremely unsuccessful. I thought it was as simple as combining soap and water, but I guess there was a little bit more to it than that. So I thought I'd give my friend Dr. Margaret Landis a quick call. She's an organic chemist at Pfizer. She led the team that created Paxlovid. That's the cure for COVID. So I thought she would be the perfect person to help me figure out why my bubbles are failing. Hey Meg, welcome to the podcast.
Meg: Thanks, Zim. It's always great to be on your podcast. What are you doing on this cold day?
Meg: On this snowy, cold day, I am shoveling my sidewalk just to try to keep ahead of the snow and baking, because most organic chemists are bakers, because baking is all about organic chemistry too.
Zim: I never put that together. I was always wondering why you're always baking. Uh, so now I know.
Zim: Now, the other thing to note about Meg is she went to Antarctica with me, and she's an avid amateur photographer. So she's the perfect person to have this conversation with. And maybe after this conversation, you'll feel inspired to head back out and try photographing soap bubbles today?
Zim: So what are the ingredients I need to make soap bubbles that are not going to just burst on me in the cold?
Meg: So the key to making durable soap bubbles that are going to last long enough so you can photograph them is to add things that will increase both the viscosity and the surface tension. And that will serve to make them both more durable so you can blow them and maintain their integrity. And then they'll last longer, so they do have a chance to freeze. In normal bubble solution, you would think of just a detergent and water.
Meg: In this case, we're adding two extra ingredients. One is glycerin, and one is corn syrup. Those are going to interact very well with the water in the system. They're going to both increase the viscosity, and they're also going to increase the surface tension.
Zim: Quick question: what exactly is viscosity?
Meg: So viscosity is a measure of the thickness of a fluid as it's flowing. It's a scientific term for really the measure of internal friction within a liquid as it flows.
Meg: For normal sort of examples, water has a fairly low viscosity, so it flows very well. But then you can think of things like maple syrup, corn syrup, or honey, and those fluids we say have a higher viscosity. If you try to pour them, they pour very slowly. The molecules in those liquids are interacting strongly with one another, and so they're not wanting to sort of move and flow like water.
Zim: So the problem that I've been having is I've only been adding soap to water, and my bubbles were popping fairly quickly. And what you're telling me is this is why I would want to add glycerin and corn syrup to my mix.
Meg: Correct. If you've seen examples of where they've blown the giant bubbles, normally it's just water, glycerin, and soap. But in this case, adding both the glycerin and the corn syrup, you're adding two ingredients that are really raising the surface tension so that when you blow the bubble, the bubble is going to have much greater strength in the skin of the bubble, because the molecules in that shell of the bubble are interacting much more strongly with those two additives than they would if you just have soap and water.
Zim: Meg, do you think there's an optimal recipe for the solution?
Meg: Like I said, I haven't personally experimented myself. But what it looks like online is starting with one cup of water, with distilled water being the best, because that removes some of the ions that can lower the surface tension. The best recipe that I can recommend, perhaps, is one cup of distilled water, two tablespoons of dish soap. I would definitely use the good soap, so Dawn. And then it looks like one tablespoon of glycerin and then one tablespoon of corn syrup. That's the most common recipe that I'm seeing online.
Zim: I'm sorry, why is Dawn the good dish soap?
Meg: The sort of better dish soaps are going to just have less other ingredients that aren't surfactants. Dawn is generally going to be a better quality surfactant with less additives that can interfere with the bubble formation. So it's just a higher quality dish soap. It's probably more purely a surfactant mixture, just better overall success for your bubbles in the end.
Zim: I'm sorry, Meg, what the heck is a surfactant?
Meg: So a surfactant is basically another sort of word for soap. It is a molecule that helps remove dirt and grease. It has one end that likes to interact with water and one end of the molecule that likes to interact with grease. And then as you rinse with water, it's able to carry that grease or dirt away from your dishes or from your hands, whatever you're trying to clean.
Zim: Do you think I need both glycerin and corn syrup?
Meg: I think yes, because like I said, you're using now two ingredients to really increase that surface tension and keeping the bubbles around long enough to freeze.
Zim: The other thing I was advised to do was to let my solution sit for an hour before using it. What are your thoughts on that?
Meg: There's not any real chemical reaction happening. It's just these liquids, and these components are highly viscous, but they need to be mixed very well. And you need to form a very homogeneous solution with all the components mixed well.
Meg: So in my opinion, the sitting for one hour really is just giving the solution a chance to mix well so that when you start to blow your bubbles, you're going to have a higher success rate for keeping those bubbles sort of formed and able to freeze.
Zim: But if I think that I've mixed my solution quite well and everything has come together, I don't really need that hour, right?
Meg: Correct. Be careful when mixing the solution. As you know, it has detergent in it. If you try to mix it very vigorously, you may just get a lot of foaming.
Meg: So it's a trade off. If you can swirl well to mix or gently invert the mixture to mix it well versus shake vigorously, that's probably the best way to get it mixed without creating a lot of foam in the system. So yeah, then you shouldn't have to wait the whole hour.
Zim: Okay, so I will keep that in mind.
Meg: So Zim, have you thought about adding any color, food coloring, to that bubble mixture and making frozen colored bubbles?
Zim: What a great idea. Do you think that's going to mess up the viscosity at all?
Meg: No, you really only need a small amount of food color. Regular water-soluble food color should work. And just as long as you're using a small amount, really you have so much of the glycerin and the corn syrup that really that small amount of food dye should do nothing. Feel free to add just a small amount of any food color of any color you wish.
Zim: Well then, that's a lot of science today. I have now taken all the fun out of shooting soap bubbles.
Meg: No, you put the science fun back in.
Zim: So I'm going to let Meg go run out and give it a try, and then I'll be right back with instructions once I've worked everything out. Meg, thank you so much for joining me on this very cold day.
Meg: Yes, great, Zim. Have fun. Everyone get out there and try it. It's a great science experiment.
Zim: Well, it's a great photo project, right, Zim? I agree with you. The best projects are science and photography together.
So after I spoke with Meg, I went out and started experimenting, and here's what I learned. First, I thoroughly mixed the cornstarch, glycerin, and water. By adding the soap last, I was able to minimize the foam, which made the solution much easier to work with. I then put it outside so it could cool down before I started. By starting with a cold solution, I didn't have to wait very long for the crystals to start forming.
Next, I prepared my shooting surface. I actually started with an upside-down wok that had a flat bottom because it was black and I didn't want light bouncing back up into the bubble. By doing that, it gave the ice crystals a little bit more definition, and it worked great. I also chose to use the metal wok because I knew I could get it cold quickly, and I knew it would stay cold while I was shooting. I found that if the shooting surface was warmer than the air, the crystals took much longer to form.
After that, I switched to shooting on snow because I was hoping the cold surface would encourage crystals to form from the bottom up. I found that most of the time, crystals formed from the top down because of the cold air. Unfortunately, what I found was snow alone didn't work, since the snow just soaked right on in. So I took a hot spoon and I melted the top layer just a little bit, and I let it freeze into ice. That gave me a solid surface, and that worked really well.
Unfortunately, the surface was so cold, the solution often froze on contact. So my workaround was to blow a bubble into a spoon first, then transferring it onto the surface and gently blowing more air into it to make it a little bit larger. Since I had a slight breeze, I had to keep the bubbles a little bit small, about one to one and a half inches. For me, larger bubbles didn't last long enough to photograph. They often popped before any crystals could form.
For my camera settings, I shot in manual mode at f/8 to ensure I had enough depth of field. My shutter speed was 1/125th or 1/250th of a second to stop any movement because of the breeze. And then I left my ISO on auto because the light kept on changing on me.
I also tried Meg's suggestion of adding food coloring to the solution, but it didn't really work well for me. I realized the bubble itself was too thin to show the color. So what started as a chemistry problem turned into a physics problem. So then I thought I would try coloring the ice I was shooting on and lighting it from underneath. So I placed a bright flashlight in the snow underneath the bubble. And surprisingly enough, it did add a little color to the bubble. Not much, but some. I think it's definitely going to take a little more experimentation with coloring and light to get it where I want it.
The last thing I tried was focus stacking. But between the wind and how fast the crystals were growing, it was difficult to pull off. Once freezing starts, the crystals grow really fast. The upside is that this is a cheap experiment you can repeat over and over and over again. Unfortunately, you can't predict the crystal patterns. And while that's part of the fun, it's also part of the frustration.
And finally, my last piece of advice is to dress warm, bring extra batteries, and be prepared for the cold. If it's cold enough to freeze bubbles, it's cold enough to make photography uncomfortable. But if you pull it off, it's really worth it.
Safari Gift Certificates
