Experiment

Photo courtesy of Nick Lott.

What do a cup of cappuccino and drilling for oil have in common? Foam.

Our story begins when Schlumberger engineer Tony Veneruso made himself a cup of cappuccino. As he sat down to take a first sip, he noticed that the foamy milk topping had collapsed. “That’s odd,” he thought. Tasting the coffee revealed that he had inadvertently dusted the drink with nutmeg rather than cinnamon, as he had intended. Did the collapse of the milk foam have something to do with the substitution of nutmeg for cinnamon?

Tony quickly assembled his research team—his three grandchildren—and began a series of experiments. He also contacted SEED Educational Programs manager Michael Tempel, who sent an inquiry to the SEED experts, the hundreds of Schlumberger volunteers who answer the questions submitted to the SEED Web site’s Ask the Experts section.

Schlumberger scientist Mathew Samuel not only shed light on the question but also launched his own research program along with colleagues Leiming Li and Lijun Lin. In the oilfield there are situations in which foam can be a problem, from bubbly drilling-fluid mixtures to foamy cement. Traditionally these foams are broken up with a variety of chemicals. Mathew, Leiming, and Lijun saw the possibility of alternative, environmentally friendlier defoamers.

Over the following weeks and months our researchers came up with a variety of defoaming experiments you can try for yourself. They also systematically investigated the feasibility of using nutmeg and other substances as defoamers in the oilfield. So far there have been three patent applications filed for environmentally friendly defoamers, with more on the way.

Background

Before describing our experiments, let’s be clear as to what we mean by foam. In addition to the milk foam on the cappuccino, you are probably familiar with soapsuds and maybe whipped cream, meringue, or other light foamy deserts and toppings. These substances all consist of many bubbles of some liquid filled with a gas, usually air.

Tools and Materials

• Note: How to separate eggs The experiment calls for three egg whites, which means you need to separate the white from the yolk for each of the eggs. To do that, you crack the egg over a bowl and let the yolk settle in one half-shell while the white goes into the bowl. Gently pass the yolk back and forth between the two halves of the shell, allowing more and more of the white to run into the bowl. Once the egg is separated, put the yolk in another container for use later in cooking.

  Cinnamon powder

• Nutmeg powder
• Masala powder
• Mustard powder
• Milk, preferably low-fat or fat-free
• Shaving cream
• Whipped cream
• Three egg whites, uncooked (see note)
• Dish-washing liquid
• Hand-cranked egg beater
• Straw
• Four drinking glasses
• Shallow bowl
• Three plates
• Milk shake blender or any regular blender

What to Do

We tried a number of different substances that foamed and a number of different spices to see what worked and what did not.

Whipped milk For our first experiment we whipped some milk with a hand-cranked egg beater to produce foam. We poured equal amounts of the foamed milk into each of four glasses.	Masala Plain   Nutmeg Cinnamon
Each glass was assigned a spice powder, with one glass left plain as the control. Next we gently sprinkled equal amounts of cinnamon, nutmeg, and masala powder into their assigned glasses. We watched carefully and compared the defoaming action.	Masala Plain   Nutmeg Cinnamon
After about five minutes the powders clearly started defoaming the milk, with the nutmeg having the most effect.	Masala Plain   Nutmeg Cinnamon
By ten minutes into the experiment, the foam in the glass with nutmeg had just about reached the liquid level of the milk. In the glasses with cinnamon and masala, the foam was somewhat reduced. Considerable foam remained on the untreated glass of milk.	Masala Plain   Nutmeg Cinnamon
After 15 minutes it was clear that defoaming had taken place. The milk in the nutmeg glass was flat—no bubbles—while a bit of foam remained in the glasses treated with cinnamon and masala. The untreated glass still had quite a bit of foam.	Masala Plain   Nutmeg Cinnamon
We decided to test milk in a slightly different way, to see if the defoaming effect was related to our having used drinking glasses. We put the milk into a shallow bowl and whipped it up with a hand-cranked egg beater.
Then we sprinkled nutmeg at one side and cinnamon on the other, leaving an area in the middle unpowdered. The nutmeg, at the left, collapsed the foam. The cinnamon had little or no effect.
Shaving cream and whipped cream For our next round of experiments we tried two foams that are sold in pressurized cans: shaving cream and whipped cream. We tested nutmeg and mustard powders as the defoamers.
We put a blob of shaving cream on each of three plates. We left one plate alone, to be the control plate; sprinkled mustard powder on the second plate; and sprinkled nutmeg on the third. After one hour there was no observable change. All three blobs of shaving cream remained fluffy.
We tried the same test with whipped cream, and the result was essentially the same. After one hour there was a slight subsiding of the whipped cream on all three plates, with some liquid appearing around the edges. There was no difference between the plain whipped cream, the one with nutmeg, or the one with mustard.
Dish detergent Next we tried dish detergent. We put water and a bit of detergent into each of two clean glasses. To create foam, we put a drinking straw into the liquid and blew air into the mixture to add bubbles. We sprinkled nutmeg into one glass and left the other alone. After a few minutes there were fewer bubbles on both glasses, but there was no difference between the two. We then blew through the straw again into each mixture. We thought that maybe the effect of the nutmeg would be greater now that it was thoroughly mixed in with the water and detergent instead of just touching the surface of the top bubbles. Again, the bubbles broke over time, but there was no difference between the two mixtures. Egg whites Our final experiment was with three uncooked egg whites, which have been separated from the yolks (see note ). We whipped the egg whites with an electric malted machine. A stick blender or regular blender would work equally well.
We distributed the whipped egg whites equally into three glasses and sprinkled nutmeg on one, mustard on a second, and left the third alone. We could see that in the glasses with mustard powder and nutmeg powder, bubbles at the surface were broken. There was a craterlike effect, creating a depression on the surface, that did not occur with the plain egg whites. After a few minutes the volume of foam appeared to be a bit less in the glasses with mustard and nutmeg than in the glass with just egg white.
But what if the bubbles were being broken simply because the grains of powder were being dropped on them? The observed result could be because of a physical popping of the bubbles rather than a chemical reaction. To test this hypothesis, we used the approach we had taken with the dish detergent. We whipped the egg whites with the powders already in them. Again it appeared that the foam held up better with nothing added. Mustard broke the foam somewhat, but nutmeg was a slightly better defoamer.
Now that you have seen what we did, try these experiments for yourself. Can you think of other foams you might try? Would homemade whipped cream (milk and sugar, beaten until frothy) behave differently than store-bought? We tried dish detergent, but what about soap? What other powders might work as defoamers? How about powdered detergent or bath powder?