Thursday, May 10, 2012

Light-bulb Moments and Solar Cookery.

My recent post on Simulated Baked Goods stimulated a little email and blog correspondence. It clearly triggered childhood memories for a few folk (in the USA) who remembered with fondness a child’s toy oven that actually cooked cakes and cookies via the heat of a light-bulb. It was (or maybe still is?) sold with various special packet mixes which perhaps were formulated according to the simulated baked goods concept. The only non-commercial example I am aware of that uses this concept in cookery is the raising of bread dough in a cupboard lit by a light-bulb.

I had a toy oven myself as a child – or rather, a toy cooktop which actually cooked with lighted methylated spirits. I don’t think it would pass any health and safety legislation today. I also remember some experiments with cooking in the sun using folded sheets of aluminium foil (and the associated idea of setting paper alight by using a convex lens) but I don’t remember the dishes so prepared, so presumably they were not a success. Then again, I grew up in the north of England which is not noted for its abundant sunshine. I now live in sunny Queensland, where it is ‘beautiful one day, and perfect the next’, so I should perhaps revisit the experiments.

Humans have been interested in the energy from the sun since ancient times, but the first person to actually record his experiments in solar cookery was a Swiss naturalist, Nicholas de Saussure (1740-1799.) The principle was simple and enduring: several concentric glass covers positioned over a box with a blacked and therefore heat-absorbing lining. It is said that he was able to achieve a temperature of 320 deg.F, and that in it he made some quite satisfactory soup.

An astronomer, John Frederick Hershell (1792-1871), was the next determined solar energy enthusiast. On an expedition to the Cape of Good Hope in 1837, he cooked in a mahogany box with a double-glazed top, which was buried in hot sand, and apparently reached a cooking temperature of 240 deg.F. It appears that he used it regularly, and was able to prepare ‘a very respectable stew of meat’ which was ‘eaten with no small relish by entertained bystanders.’

We then come to M. August Mouchot, a French mathematics professor and solar cookery enthusiast who received a patent from his government in 1861 for his marmite solaire. The oven used a burning glass (convex lens) to focus the heat into an insulated jar, and could be used for distilling brandy and making coffee – and  presumably other things too, if I could read French properly and took the time to search.

There were other keen scientists, and experiments went on, and no doubt are still going on, as they should – but the basic principles will not change. A solar oven requires something to focus the sun’s rays, and an insulated receptacle for the food. That is all. One of the stimuli for the interest in solar energy use in the nineteenth century was the awareness that fossil fuels are non-renewable. We are still having the same debate, only with a little more urgency now. There are a myriad other reasons for using solar energy in cooking too: live forests are not renewable at the same rate as we are destroying them for wood, animal dung is better used as fertiliser, and there is no fire risk (unless you play with your convex lens and light pieces of paper, of course) and no ash. And, once you have made your modest investment in making your oven – it is free.

In case you need a little more persuasion, I give you the words of several non-scientists who have tried the experiments themselves. From a small book called Solar heat, its practical applications by Charles Henry Pope, (Boston, 1903), here are a couple of extracts:

The writer, in Farmington, “ … in 1883, dug a hole in a snow-drift, shaping it in a general parabolic shape with a shovel, and raised the thermometer 60 above the temperature of the surrounding air in a cold day. A scientifically constructed mirror of this sort, made for the Arctic traveller or the resident of a northern clime, and placed on a sled, could be turned to face the sun, and obtain a temperature hot enough for water-boiling and cooking very easily. If the sun can blind the ordinary traveller by its glare, and cause violent optical disease to those who dwell upon its whiteness, it can be made to atone for its cruelties by doing service as a fuel and a kinetic.”

The author also included the text of an article published in the Scientific American on June 5, 1898:-

To the Editor of the Scientific American, June 5, 1878
"I send you a short account of my experiments, made in Bombay, on the utilization of solar heat for cooking…. It consists of a conical reflector, made of wood and lined with common silvered sheet glass. Inside there is placed a copper cylindrical vessel, covered by a glass cover. The cooking vessel is raised about four inches from the bottom, and the glass cover is five inches longer than the vessel, and two inches wider, which leaves an interval of four inches of hot air under the boiler, and one inch
all round and at the top. The wedge under the apparatus is to keep it inclined, so that the rays of the sun may fall perpendicularly on the boiler”
“The rations of seven soldiers, consisting of meat and vegetables, are thoroughly cooked by it in two hours, in January, the coldest month of the year in Bombay, and the men declare the food to be cooked much better than in the ordinary manner. Several people in Bombay and in the Deccan have tried it, and always with success. If the steam be retained, the dish is a stew or a boil; if it be allowed to escape, the food is baked. … I have a letter from a surgeon-general in the service, which informs
me that he cooked a leg of mutton in it, and that it ' kept hot for four hours ' after having been removed from the air.”
Mr. W. Adams.

I have not quite finished with this topic. I am unable to resist giving you the words of the wonderful Dr Jonathan Swift (1667-1745) on solar cookery in tomorrow’s post.

Recipe for the Day.

Solar cookery books are too ‘modern’ for this blog, and special recipes are not required. In honour of Nicholas de Saussure, I give you Swiss Soup (from an American cookery book.)

Swiss Soup.
Five gallons water, six potatoes and three turnips sliced; boil five hours until perfectly dissolved and the consistency of pea soup; filling up as it boils away; add butter the size of an egg, season with salt and pepper, and serve. A small piece salt pork, a bone or a bit of veal or lamb, and an onion, may be added to vary this soup.
Practical Housekeeping: A Careful Compilation of Tried and Approved Recipes, by Estelle Wood Wilcox (Minneapolis, 1883)

Quotation for the Day.

I'd think that anyone who truly wanted to end world hunger would donate his or her body to culinary science.
Kevin Wickart.

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