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Ellen McCallie's Carriacou diary: Feel the heat

Updated Monday, 28th January 2008

Caribbean islands tend to be a tad warm! Find out how Ellen fared with her homemade sunblock.

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Day 1

My main challenge is to make a skin cream to protect us from the sun’s damaging rays (UVA and UVB)

Sub-challenges to support other scientists:

  1. Make an indicator dye for Kathy’s thermometer
  2. Figure out an insulating material for Mike and Mike’s ice maker
  3. Make a sealant for Mike B and Mike L to use in their ice maker
  4. Find a lubricant for Jonathan’s thermometer

What a fabulous day! This is exactly what I love about botany, science and life! Kate and I wandered through a tropical deciduous forest. This means that although the air temperature stays relatively constant throughout the year, the rainfall varies enough that during the dry season most trees lose their leaves, just like in the temperate zone. When the rains hit again, the trees leaf out. Here it is six months of wet season and six months of dry. We are currently entering the wet season, so we should be able to watch the island "green up" nicely. Because we are near the equator, it is always warm (hot) and the day length is always about twelve hours.

So back to the challenges. I am actually very glad that I got to focus on getting things for other people today. The sunscreen/sunblock challenge seemed daunting this morning - impossible, really. Now, after a day of wandering through a healthy forest with plenty of diversity, I feel like I’ve been "shopping" for products and possibilities. I’ve got several ideas, so I feel a lot better. I need to check these with Mike B before I proceed, though.

The inert base for the sun cream should be done by tomorrow morning. The oil I squeezed out of the coconut 'meat' will float above the water when they separate. It’s just like vinegar and oil salad dressing. I’m not sure about the resin we tapped from the bursera tree - the one that smelled like incense. The wet season isn’t here full force yet, so the tree may not have enough fluid to make sap. I doubt I’ll get more than just an ooze but I’d hate to be wrong and lose any, hence the little cup made from the calabash fruit shell. In addition, Mike B wasn’t sure how he’d use it. It definitely will not withstand the heat of the kiln but maybe it will be used at room temperature. More importantly, can I 'cure' it well enough to make it hold.

In terms of the thermometer indicator, I did see a couple of trees with potential. Also, I’ve begun to think about newly ripened calabash fruits. I just need time to play and figure out a couple of things.

Again, this is like a dream. I can’t think of a more fun way to spend a day than exploring a healthy forest and figuring out what the plants might be useful for. I must say that Kate is great. I think she really got into it - sniffing tree trunks, using machetes, etc. It was relieving that she didn’t expect me to know all the answers. Science is a process, not a bunch of facts. Plus, I’m not very good at just memorizing a bunch of stuff. I work contextually. I remember things because I’ve seen, smelled, touched or worked with them before. Kate allowed me time to try to figure things out. For example, the big tree with the buttress roots or the molt of the scorpion that I first thought was a dead spider. She didn’t demand that I know things right off: she let me examine the stuff and think a bit.

I sometimes imagine we’re explorers in a new land. I feel like my mind spent the day bending around ideas and dancing. I can’t wait until tomorrow.

Day 2

I’m bruised, I’m bug-bitten, I’m physically exhausted but I’m happy. Not everything went smoothly today. So much to do.

The good things:

  1. Drew, the camera guy, and Paul, the sound guy, are delightful, good natured, and physically very strong. They are here to make a good programme on science. They aren’t trying to make us look ridiculous - we can do that on our own.
  2. It turns out that Kathy needed some sealant too. I fiddle a little and figured out which branches to cut in order to get sap to flow well. I will now be able to make one sealant glob in about 30 minutes (20 minutes of dedicated collection and 10 minutes of preparation). If I add lime juice (acetic acid) and heat, the latex gets gummy, but stays soft. Very exciting.
  3. Also it is best to cut vigorous young green vines. Second best are vines (brown or green, thus either old or young) that are growing horizontally. I don’t understand why yet, but they give more latex.
  4. Mike B’s zinc oxide idea is fabulous. Can you believe it that we are filing the zinc off nails in order to heat it (get it to mix with oxygen in the air) and then smear it on our bodies? My Aunt Maddin is going to really laugh!
  5. Lime oil is a sunscreen possibility! Logic says that the lime oil sunscreen is unlikely to work. I think this only because it is so available, yet it is not used commercially for sunscreen. But oil in the rind of limes contains anthrinilates. Many sunscreens contain anthrinilates as active compounds to absorb UVB rays. It is worth a try. You never know, Rough Science Lime Oil Sunscreen may be the next big sell!

I can’t believe I forgot to clarify the coconut oil for Jonathan. Thank goodness he didn’t end up using it. At least it is now clarified for the sun creams. If I had mixed the unclarified stuff into the sun cream, it would have been a sweet but sticky and bug-attracting mess! Funny how I just looked at the mixture, completely confused as to why I wasn’t seeing pure oil. It wasn’t until I rubbed it around on my hand that I identified the problem… those five senses save me all the time.

I think the colourant for the thermometer is fun. It isn’t ideal or really permanent but it does show that some colours are soluble and stable in alcohol and others aren’t. I did try heating the cactus fruit mush - it turned brown when boiled. The flesh is bright magenta. I was disappointed that there were no cochineal insects on the cacti. They are supposed to make a great, bright red dye when crushed.

About the insulation making - it was hilarious. I went back out for a second bucket of dung and two cows immediately produced some extra-fresh stuff for me. Heck, one cow was near enough to go in my bucket.

I do think Jonathan has an excellent point about wet and dry insulation. I may try coconut husks alone tomorrow. There is moisture in the current ice maker insulation and water is really tough to get to change temperature.

There is so much more but I am falling asleep.

Day 3

It was about 4 o’clock in the afternoon – the sun was soon to set, so this was the real test for the icemaker. As Kathy and Jonathan had their challenges whipped, they were now full time consultants on ice. All of a sudden, from separate directions Jonathan, Kathy and Mike L converged in the center of the lime factory. It was if they’d all been thinking about the same thing at the same time. The topic? (Remember, we are scientists getting to play – and to try out these ideas.)

  1. The size of the container that held the bottle for ice to form around
  2. The insulation

I could almost hear their minds pounding, churning. Bells, whistles, lights - yes, no, try this, no, but that will work, oh, that’s perfect except for..., hum, I don’t know. This is science – the intensity in figuring, in trying, in not quite knowing. A pleasure.

So after much discussion, the decisions:

  1. The bottle needs to be put in a can so the water can be contained close to it. The can, an old steel food can, will be filled with dry polystyrene.
  2. The rest of the container should be filled with dry cow dung and clay (kaolin), as it is probably a good insulator.

This set up will give ice the best possibility of forming in our hot, humid, simple conditions.

It was quite amusing when these three looked at me – their minds needed outside input and I happened to be standing there. What did I think? I could only do the basics and I am a bit shaky on those.

Dry air changes temperature more quickly than moist air or water. It takes more energy to change the temperature of a "packet" of water than a "packet" of air. Thus the immediate surroundings of the bottle should be air plus something that can "hold" the temperature change as it happens, hence the polystyrene.

We want the warm bottle and water to quickly be able to lose heat thus become cold. So the "basics" on this was in sync with their higher level discussion.

In terms of the second layer of insulation, I get all confused. But that was fine because their minds had rested and they were ready to retackle the problem. Funny how what they really needed was a moment of concentrated focus on the same topic of discussion, but a different voice. That’s why bouncing ideas off of others, even if they aren't specialists in the area, is useful.

This is one of the greatest things about multi-disciplinary collaborations. The 'non-specialists' are focused on the basics and can keep the 'specialists' grounded when they wander off track.

In any case, I provided nothing new or exciting, so, now rested, they picked back up, full steam ahead to recapitulate and reconsider their decisions. Then, just as they had come together, they dispersed to different parts of the lime factory to each make part of the final design. Where is the camera when you need it?

So what is so confusing about the second layer of insulation? First, it must 'hold' whatever change takes place within the center of it. Does it need to change temperature or just hold the temperature? Both, first change and then hold. How does something that is good at changing temperature then become good at holding it? I don’t know how to get my mind around these questions.

I must say that Mike B is a saint. In the heat and humidity he collected fuel wood, kept the kiln and/or several fires going to distill, combine, purify, etc. He must be toasted, yet his disposition is still so pleasant. (The crew also was invaluable in collecting wood and starting and keeping fires going. What we really needed was a full-time fire person or a bit of electricity… I can’t figure out how people who depend solely on wood get everything done without letting the fire go out!)

As I finished my challenge by noon, I got to watch and help everyone else. For Mike B, I watched bubbles. I was supposed to get him (he was making something else react) if the bubbles stopped or if they increased significantly. Basically, he was adding ethanol to sulfuric acid and making ether. The reaction only occurs within a narrow temperature range, so he had the acid in a sand bath over a fire. Sand is a good insulator. It absorbs heat evenly and distributes it. Sand does not change temperature quickly, so if the fire gets really hot (adding more wood) or cools a bit (the wood burns down), the sand temperature is slow to change. This keeps the flask with the acid and alcohol at a pretty constant temperature so the reaction takes place.

Finally, I should talk about the sun cream challenge. I think the lime oil has potential! That’s pretty exciting. The success was bitter-sweet, however. Wherever the sun cream wasn’t, I am fried. It stings, hurts, burns…

The day was overcast but we had to try our kaolin clay sunblock (a physical barrier to the sun’s rays) and the lime oil sunscreen (a chemical that is absorbed into the skin that then absorbs the UVB rays of the sun before your skin does). So in a physical barrier, the sunrays do not reach your skin. The barrier, clay in this case, reflects most of them and absorbs the rest. In the chemical barrier, the product is absorbed into the skin. When the UV rays, UVB in this case, strike the skin they are preferentially absorbed by the chemical product not your cells.

These chemically active sunscreens are preferred to physical sunblocks because the sun blocks form an outer layer on your skin. You see sunblocks but you don’t see anything but the effects of sunscreen.

We knew that UV rays still come through when it’s cloudy, so Kate and I applied the creams and laid on the beach. The sun came out for the last thirty minutes. The problem was that I wanted to see change – the effect of wearing the sun creams, yet I had little to no control over the exposure. I couldn’t measure the amount of UV light hitting us. I made a poor judgement call, though. I should have talked it through with someone not involved in the challenge before we laid out. It’s too late now but I have learned from this experience. (It is no excuse that they were all busy. Had I asked for five minutes of advice, they would have gladly given it.) This is the problem of working alone or in your own bubble.

In any case, Kathy saw us at lunch time and came out to the beach to get us out of the sun and go for a swim.

Kathy really saved us, particularly me, as Kate had had to check on the others periodically. Kathy make many good points:

  1. "Getting out of the sun is erring on the side of safety. We all know that the midday equatorial sun is strong. You’ve been at this over an hour."
  2. "Ellen, your legs are almost always covered. You are not one to lay out or promote a tan, so you are going to be particularly sensitive. This is stupid, get out of the sun."
  3. "If you are trying to show the efficacy of a mild sunscreen, you shouldn’t test it in extreme conditions (midday on the equator). You should test it in appropriate conditions (morning or late afternoon when the sun is strong, but not deadly)."

Kate concurred. I was stubborn for about ten more minutes as I mulled things over in my head. A little voice kept saying, "But I have to see RESULTS!" Safety had got to be first, so Kate and I took a mad dash across the blistering sand (this should have been an indication for me) and hit the ocean. We rubbed off the suncreams and checked for their effect. We screamed and danced with delight. The rest of the team was up in the lime factory and thought we’d gone a bit nuts. We decided not to tell them of our smashing success with the kaolin clay and with the potential success of the lime oil. I say "potential success" of the lime oil because the areas of skin with the lime oil sunscreen were not as sunburned but the skin looked irritated, like the lime oil itself was hard on it.

At the same time that we were excited, it was also obvious that I had made an error in judgment. My legs were really burnt, probably second degree. I figured I’d use lots of aloe and calabash to help them heal.

At the end of the day, the ice team had made drastic improvements but we only got condensation, not ice. Bitter sweet – each component worked well but the synergistic effects were not good enough. No ice.

That is science and the process of trial and error, however.

Over dinner we couldn’t help but brainstorm about potential improvements. But our time for that project was up. Kathy was right on all accounts. Kate got red but I turned the color, texture and temperature of a boiled lobster. DO NOT TRY THIS AT HOME!





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