axel, Author at dadblog

boiling eggs in the mountains – a holiday science lesson

(Taken from an email exchange after a recent holiday)

A huge problem we experienced while on a mountain holiday with a group of friends that caused an untold amount of heated debate, soul searching and hungry kids- cooking oeufs a la coque at altitude (boiled eggs for the unsophisticated).

We were in the mountains and had a terrible issue at breakfast. The Wife and kids decided to have boiled eggs to get a good start to the day. The mountain air was bound to make us hungry.

Usually the Wife keeps a very very careful eye on the time, 3½ minutes exactly, for her perfectly runny soft-boiled eggs.

But, when the eggs were pulled out of the pan, dipping soldiers at the ready, shell cracked open with a knife so the break is nice and clean, to our horror the egg was completely raw.

And now the eggs were open it is difficult to put them back in the boiling water to cook. It turns into some sort of poached-mess which you can’t dip the soldiers into. Not a good start to the day.

Somehow after this egg disaster the next day we tried boiled eggs again. But this time we added a bit of extra cooking time. ‘cos we ain’t dim

at 4 minutes we still had raw eggs.

The soldiers were getting restless.

Not to be deterred the next day we had another go. This time we only pulled one egg out at a time. After 5 minutes we still had an under-cooked egg.

At 5½ minutes the next egg was still under-cooked.

This was now getting serious, and number 2 was beginning to question the Wife’s egg boiling expertise. Which is very dodgy territory.

After 6 minutes the next egg was cracked open rather tentatively.

Bingo! A perfect soft-boiled egg. The rest were quickly served up to an eager gang at the breakfast table. The soldiers were a bit soggy but there were not too many complaints. After 3 days we had mastered the breakfast soft boiled egg challenge.

But, this saga started a discussion among the engineers in the group. And there are quite a few of them… Unfortunately, I couldn’t really help as I only work in powerpoint.

What was the calculation required to adjust the egg boiling time at altitude? And why? How did it go from 3½ minutes to 6 minutes? Almost doubling in cooking time. Obviously altitude/air pressure was a factor, but what was the maths/science behind it all?

To compound the issue the mountain hut did not have wifi to give us the solution! (This is a completely different issue that the kids are still pursuing with Childline).

Back at home a bit of internet searching (we have wifi at home) threw up a few very interesting articles on our subject.

A neat explanation and solution was found here:

http://newton.ex.ac.uk/teaching/CDHW/egg/

This is the summary:

where ρ is density, c the specific heat capacity, and K thermal conductivity of ‘egg’. *

This looked like the solution to our boiled egg timing issue.

I took it upon myself to translate all of this into something more visual. I work in charts on powerpoint for time-challenged Execs…

altitude does have an impact.

at room temperature (on the chart – the red line) cooking an egg at home (just above sea level) takes 3.32 minutes. but in the Mountain hut it will take 4½ minutes. due to a lower temperature to boil water (due to lower air pressure). from 100*c (at home) to approx 98*c (in mountain hut). if the temperature of the water is lower it will take longer to cook. this 3.32 minutes is very close to the actual time the Wife cooks the egg. science looks like it supports the Wife.

Altitude adds about 1 minute to the time to soft boil an egg.

But this did not explain the much longer time we took to boil our eggs.

One factor the Wife didn’t take into account while cooking was the friends were in the habit of keeping the eggs in the fridge. and she keeps them in a cupboard next to the fridge.

Perhaps equally interesting is the effect of keeping the eggs in the fridge or not. This obviously affects the cooking time. This is quite a reasonable assumption as the cooler something is the longer it will take to cook.

This is shown by a jump from the red line to the blue line. thus for home it goes from 3.32 minutes to 4.36 minutes at the same altitude. a minute longer to soft boil an egg from the fridge rather than outside the fridge.

So at 2000 metres altitude, when we take an egg from the fridge and want a perfect soft boiled egg, it takes 5.38 minutes.

Thus when we combine the altitude and fridge effect together we get an extra 2 minutes to boil an egg from our original experience. (the black arrow)

While these are theoretical calculations, we saw 2½ minutes extra, the general science supports what we experienced.

The engineers in the gang certainly found this very interesting.

Although the wife commented, “You’re such a busy man !! don’t you have any real work to do?”

note* This solution does contain some approximations as some commentators have noted. For a more accurate treatment, one would need to account for the thermal properties of the white, yolk and shell are all different. The egg would need to be treated as three concentric, ellipsoids with Dirichlet boundary-conditions at the water-shell interface and Neuman boundary-conditions for the shell-white and white-yolk parts. Changes in its thermal properties when the white changes state from liquid to gel, and the latent heat associated with this change would also need to be accounted for.

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garden pea harvest

We have been trying to live the healthy-low-carbon-footprint-eco-self-sufficiency lifestyle for a bit. The wife has been trying to grow our own vegetables and fruit in our garden.

we created a small section in one of the garden boarders to grow some peas and green beans. we planted seeds in spring and have been monitoring the progress. I was in charge of watering. which I did quite well.

The wife saw that the crop was nearing harvest time and told me to inform her when we were next having peas for diner.

A few days later, peas were on the menu. I duly informed The Wife, who started the harvest.

I was very surprised that the harvest took as long as it did.

Luckily we weren’t that hungry.

women in engineering – the new sandwich filling

number 1 came home one day from school with a letter for a school trip. the usual routine – “can you sign this letter” said in a grumpy-ish tone.

“sure, what is it for?” is the usual reply, with out trying to sound to desperate or bothered so that she won’t get the pleasure of knowing we are really interested in what she is doing.

“oh, some sort of trip about women, some where.” was the detailed description we got this time.

the letter was about a trip for girls (young ladies) , to one of the world’s top universities, to try to get them interested in engineering, as part of Women in engineering day. www.eng.ox.ac.uk/national-women-in-engineering-day

obviously we signed the letter pretty sharpish, and wished her luck.

The day came and off number 1 pottered to the trip.

On her return we had to broach the usual inquisitive questions with care. Hopeful that we could get enough information to piece together what had happened without being accused of running the Spanish inquisition and invading her personal liberty.

“how was the day?” I asked gingerly

“quite good” was the reply from number 1.

Something was strange, was this the same trip that was about calculations with a load of clever people? This did not compute. At all.

“what was good about it?” I said with a bit of surprise.

“the food!”

“the sandwiches were great”

“chicken, pesto and salad” said with a real sparkle in her eyes.

“delicious”

Ok. The food was good. But what about the female empowerment and career prospects? I was not sure which order this should be in, but getting the correct hierarchy was not my top priority in that moment.

“what about the rest of the day’s activities?” there was a bit of impatience creeping in.

“quite boring” quipped number 1.

Normal service resumed.

Isambard Kingdom Brunel is safe, but at least we discovered a new favourite sandwich filling.

fathers day – fractions

Today was father’s day. Which is a strange name for it, as usually after the ceremonial breakfast in bed and card, my special treatment is over. It should be called father’s short morning respite before having to tidy the shed, cut the hedge, fix the bikes, re-grout the shower, and do a run to the tip. Day.

But number 2 was particularly cute on one of these days. We had been doing some maths home work that weekend, fractions, as I recall.

And number 2 was keen to show off her new-found skills and stated,

“daddy has one third of my heart”

“oh, who has the other parts”, i was keen to see where this maths based show of affection would lead.

I also had some odd thoughts running through my mind.

Am I the first third? or last third? Why thirds? Shouldn’t it be halves?

Number 2 looked confident and carried on.

“Daddy has one third”.

“Mummy has another third”.

I interjected at this point, “who is the third?” I wanted to be sure that we had not mistaken halves for thirds, or quarters, or some other fraction.

“pizza”. Was the rapid reply.

I guess that the maths lesson was a success.

And i suppose should feel special that i did feature in the top 3.

bed time ritual

one of the best moments with kids is when they go to bed and sleep.

one of the rituals we have is the bed time story and a good night kiss. And then they hopefully fall asleep.

With the good night kiss is usually “good night, I love you”

One evening we ran through the usual routine. Brush the teeth, story, another story, a good night kiss, I need to go to the toilet, another good night kiss. And finally,

“good night, I love you”.

Which was followed by number 2 saying,

“I love pizza”

the chicken project

Often at school they do really interesting projects. They are often not only interesting but also educational.

i suppose it must be done at quite a few schools, incubate a few chicken eggs, follow them for a few weeks, let them hatch and out pops a little cute chick.

The class was very excited with the project and we would get daily progress updates of the eggs. Finally the eggs hatched and everyone was very happy.

Number 1 was so excited by the whole thing, her enthusiasm somehow not only rubbed off on to number 2, but also The Wife.

We were going to do it at our house.

“we could let them hatch and then keep the chickens so they can lay more eggs”, the wife suggested.

She even played the economic card, “that way we won’t ever have to buy any eggs.”

“we’ll save loads of money and be self-sufficient.”

“in eggs”. piped up number 1.

It had almost been fully thought through.

To try to make the most of this I suggested we conduct some research and fully plan the project. Hoping that after a bit of effort everyone would lose interest and move on to the next idea.

Unfortunately, we had to visit the local pet shop to get some tips on the various breeds of chickens, best nest materials, types of lamps and so on.

the lady at the shop was very helpful. she answered all the kid’s questions, and even very helpfully suggested the best eggs that would definitely hatch. and if through a very bad run of luck none of the chicks actually hatched she could get us some babies to carry on the drive to self-sufficiency.

my look of panic and suggestion that our eggs would definitely hatch so we wouldn’t need to come back for any chicks, did not seem to register with the kind lady.

we gathered all the nesting material, just like the school set-up: cardboard box, fluffy insulating material to keep the eggs snug and warm, and a nice incubating light.

but getting a real incubating light might have been a bit over the top, so i volunteered my desk reading lamp, which looked as though it would work just as well.

At this point the Wife had gone off the idea of self-sufficiency but had started to distance herself from another potential pet disaster.

the rest of us were very excited, and all the pieces were in place.

we flicked the switch and we were off.

we monitored progress. everyday.

all looked well.

After a few days, I was a bit nervous that things would start to smell a bit. But there was no discernible odour to give the game away.

Time went by and the enthusiasm did not diminish. The kids were getting more excited the closer we got to hatching time.

I still might not have fully worked out how to explain the non-hatching eggs. But I still had a few days to come up with something credible.

the due day came. nothing hatched.

I suggested they might be late, as some babies don’t always arrive on time. plus there was no odd smell of rotten eggs.

after a couple of days number 1 let it out, “maybe they won’t hatch?”

“let’s give it a little longer, you never know” i tried to keep positive and hopes up.

after an extra week number 2 had given up and had a suggestion “we could cook them and have boiled eggs for breakfast. with soldiers.”

number 1 did not bat an eye, “they won’t hatch. let’s throw them away”

They had also forgotten about the pet shop lady’s offer of live baby chicks.

I couldn’t understand why the eggs hadn’t hatched. it may have been the lamp. but it could have been the eggs weren’t right. but they were the best eggs we could get. very strange.

trip to the supermarket

i like going to the supermarket. not because i don’t go very often. but because i like to check out the offers. how the stuff is displayed to attract those unsuspecting shoppers and lure them into buying something they didn’t want, or buying twice as much as they needed only to throw it away before they could use it. I keep a look out for a new gondola end display. or the multi buy that might not be as cheap as the three single packs. loads to keep up to date with.

i try to go with the kids. make it a bit of a trip. and they can help guard our collection of bags-for-life hanging off the trolley.

our local supermarket is next to a big industrial site, and the clientele might not be the most salubrious of specimens. Mick McManus would think twice about starting anything in this place.

on this occasion number 2 was with me. a tiny little four year old. she is a bit of a wanderer and you have to keep tabs on her or else she will go off the well ordered route and cause chaos. she’ll miss the fruit and veg and go straight to the meats. then to the cereals. then back to the veg. its like driving around the M25 on the wrong side.

utter chaos.

this time we were making good progress. and not too many child induced impulse purchases.

we had just got to the pasta section, when number 2 stops in the middle of the isle. and declares in her outside voice “I’ve made a decision”.

that was interesting, but had also managed to get the attention of the dozen or so people in the isle. I think we had just stumbled upon a local chapter of the Hells Angels gang. or a tattoo convention. or both.

but i was quite proud that my little tot knew a complicated word like “decision”. I think her audience was also quite impressed.

“i have decided we are leaving this shop”. number 2 was very certain. The on lookers, and myself, were curious as to the reason.

“there are too many ugly people here”

Four year olds don’t really know what they are saying. and they often struggle to fully explain what they mean. the English language is very complex.

well. we did leave.

very quickly.

and didn’t go back for several weeks. and not on that day of the week.

Easter Egg Hunt

Its one of those things you do, to get the kids out of the house, off screens, and do something healthy – like hunt for massive amounts of chocolate so that they can gorge themselves sick.

This has become something of an annual event in the family, born from a few cross-cultural Easter traditions.

The Easter bunny leaves her eggs, sometimes in bushes, under flowers and even up trees. and the signal that this has happened is the sound of the local church bells. then the kids are allowed to collect them. There are some bits that don’t quite add up, but the kids haven’t really questioned anything so far.

Even when one year the wife and kids were walking through a park and started to find loads of those really big chocolate eggs. After a fairly good harvest a couple approached them and politely suggested that they had found their eggs and could they please return them. Obviously a bit embarrassing.

We had amassed a large gang of cousins and headed off to a local park where we had heard a rumor that the traditional Easter bunny had left her eggs scattered around a well-defined area.

Not everything was plain sailing.

“why is it so far?”

“last year the bunny came to our garden. Why couldn’t she come back this year?”

“I haven’t heard the bells. That’s a mosque, it doesn’t have bells”

We finally got there and started the pre-planned diversionary tactic (playing on the monkey bars) so that Auntie Gaby could sneak off to do the egg hiding.

Finally we got given the signal that the bunny had passed. The bells were very faint, and adults could only hear them.

We finally arrived in the right area. The instructions were concise,

Gaby, “the bunny laid the eggs somewhere”.

Dad, “any other tips?”

Gaby, “near a tree”

Dad, “great, thanks. Anything a bit more specific?”

Gaby, “or near a plant”

Gaby, “or a flower”

Dad, “nice one. very helpful in a park…”

Dad, “how many are there?”

The Wife chipped in to help out, “loads”

The kids hadn’t waited for the instructions, maybe they knew what was coming, but they had scattered to the nearest bushes.

Over the next few minutes there were cries of joy and excitement. But slowly the screams were becoming less frequent.

Tom had given up and was knocking the heads off dandelions with his stick. And number 1 was searching through the medium of cartwheels.

Luckily Auntie Gabs was able to give some subtle guidance, “it might be near those trees, or those other ones, with the branches”, said hopefully

After a few vague top-tips it was clear that we were struggling to remember where the last few eggs were located.

Although it wasn’t helped by not really knowing how many we should have been looking for.

We finally got to the end.

A big sigh of relief. From everyone.

mushrooms or sea slugs – number 2

just because number 1 doesn’t like mushrooms, number 2 has also decided she doesn’t like them. really frustrating. and no amount of coaxing will change her mind.

One day I was making one of my “special” dishes. this entails chucking some random ingredients together and letting it stew/simmer for a while. I got a bit carried away and threw in some fancy Japanese mushrooms. the long textured things.

i served it up and there were some angry looking faces.

number 2 remarked that it looked like there were some odd looking things in the dish, and that she might not want them.

In a stroke of genius and quick thinking on my feet, I said that they were not mushrooms but…

sea slugs.

they did look like they might have been from the sea and they looked like they could have been slimey.

it just came out before i could really think of anything else.

but fair play, she only raised an eyebrow. and had a chew.

“are you sure they are not mushrooms?”

I was quite suprised that my Sea slug had got this far.

“definitely Sea slugs, mushrooms aren’t that long”

“they are a bit wierd, a bit too chewy”

but there were no tantrums or pushing stuff around the plate to make it look like it had disappeared or been eaten.

a bit of a result.

i must have got a bit cocky, as a few days later I tried another “special dish”. slightly inspired by Chicken Chasseur. it had Chicken. some other bits. and mushrooms.

I reconned that I had got number 2 to eat mushrooms without any adverse effects, so this time i could come clean.

On the plate it went.

But number 2 was quick this time.

“those look like mushrooms”

there was a bit of proding with the fork. i got given the suspicious eyes.

They weren’t the Japanese type but those little button ones. I wasn’t sure if i could get away with the old Sea slug routine again. perhaps baby sea slugs. before they grew up to become long and thin…

but number 2 beat me to it.

“they weren’t Sea slugs last time. you tricked me.”