Sand baths

For one reason or another, I have been browsing some details of the historic voyage of HMS Challenger, whose global exploration in the 1870s shattered all preconceived notions of what the oceans contained and set the scene for modern oceanography. On December 21, 1872, fourteen years after Charles Darwin had published his revolutionary ideas, a small converted British naval vessel slipped out of Portsmouth, beginning a voyage that would last three and a half years and revolutionize our understanding of the oceans. HMS Challenger (after which the space shuttle was named) had been converted into a research vessel. Her guns had been replaced by laboratories and her munitions stores by over 400 kilometers of rope and wire for surveying and sampling the ocean floor. The voyage covered 130,000 kilometers and cost more than $20 million in today’s money. The incentives were many, but two stood out: the needs to plan for global communication via undersea cables and to test the longstanding belief that the deep oceans were lifeless wastes. The latter was dramatically proved wrong, and the former accomplished by large numbers of soundings that first demonstrated the topographical grandeur of the ocean floors. In waters off the Pacific Mariana Islands, a depth was recorded of 8,200 meters. What became known as the “Challenger Deep” remains the world record-holder today, its greatest known depth later measured at close to 11,000 meters. Ocean chemistry, temperatures, and huge amounts of other data were collected and, with the publication of the fifty-volume report, oceanography was born.

Among the vast array of results was the demonstration that sand, albeit in relatively modest amounts, could find its way out onto the deep ocean floors. But that’s for another day. Wonderfully, essentially the entire original documentation of the Challenger voyage is available online (details below), and, on investigating the details of the scientific equipment carried on board, and the contents of the “chemical laboratory,” illustrated above, I discovered the “sea-going sand-bath”:

  

Now, the use of sand baths as physical stabilisers and thermostatic surrounds for laboratory vessels goes back a long way, and continues today. Here are a couple of examples from modern laboratory suppliers, the one on the right even providing a fluidised bed of sand.

 

The blurb accompanying an example of a modern sand bath goes as follows - “sand as a paradox”:

Sand-bath Method:

A sand bath is good for microscale procedures only, because sand is a paradox — it's a better insulator than it is a heat transfer material. The unique thing about a sand bath is the big temperature gradient that it can generate. For example, fill a 100-mL THERMOWELL (use no other size heater) with quality sand, operate it for at least 20 minutes at the maximum 40% power (75v or 145v) and the temperature of the sand's surface is about 100°C , and the bottom of the sand bath is almost 400°C. Touch a small test tube containing 1 mL of water to the sand surface and you get gentle heating, but push the test tube down to the bottom of the sand bath and the water boils in a few seconds.

So, the wondrous performance of sand in this way also explains its widespread historical use, particularly for “delicate distillations” – in the infernal labs of the alchemists. As described by a modern practitioner, Robert Bartlett, in his history of, and practical guide to, the dark arts:

The third degree of heat is called the Balneum Arena or sand bath. It is set up like the water bath but it is able to maintain a higher heat than the water or ashes. Many oils and substances with boiling points higher than water can be heated and distilled with the sand bath. It provides and even heating of the matter and avoids hot spots from developing. In fairly high heats, the sand bath also lends support for the vessel which might otherwise become deformed from the heat.

An eighteenth-century translation, “Written for the use and employment of the Lover of the Noble Hermetic Philosophy,” of a work written six hundred years earlier describes a toxic recipe following the misguided belief that arsenic, particularly in large quantities, had beneficial medicinal properties (a belief that contributed significantly to the mortality rate among alchemists):

 Let it be purified thus: Take of the Crystalline Matter sublimed; Let it be ground upon a marble, with an equal part of Calx of Luna, and let it be put into a Vial sealed, and set in a Sand bath again, the first two hours with a gentle Fire, the second with a stronger, and the third with one yet more violent, and increased till the Sand will hiss, and our Arsenic will be sublimed again, the starry Beams being sent forth...

Do not try this at home.

In the eighteenth-century, The Universal Magazine of Knowledge and Pleasure, provided “News, Letters, Debates, Poetry, Musick, Biography, History, Geography, Voyages, Criticism, Translations, Philosophy, Mathematicks, Husbandy, Gardening, Cookery, Chemistry, Mechanicks, Trade, Navigation Architecture and Other Arts and Sciences, which may render it Instructive and Entertaining to Gentry, Merchants, Farmers, and Tradesmen.” “Chemistry” was, of course, primarily alchemy, and, in 1751, in a section titled the “Third View of Practical Chemistry,” the following detailed illustration appeared (my thanks to the BibiOdyssey blog for the source):

 

The game is “spot the sand baths.”

According to the key, there are seven:

A, a furnace for distilling in balneum mariae.
B, a furnace for making spirit of hartshorn, &c. in great quantities, e, its head, and b,b, two receivers.
C, a sand furnace; d a retort placed in it.
D, another sand-furnace, having a copper distilling body placed in it, to which it is fitted (d) a glass head, and (e) a receiver.
E, a small open furnace for divers uses, as boiling syrups, evaporating liquids, &c.
F, a wind-furnace, blown by the bellows, M, f a cucurbit in a copper vessel with sand, placed over the furnace.
G, a sand-heat, with a retort and a receiver.
H, H, two sand-heats, in each of which is placed a retort k, m, for distilling volatile spirits, one of which has a single receiver l, and a double one i, k.
I, a cold still; n and o the receiver.
K, a sand-heat, in which a retort q, having a large receiver p fitted to it for making sal volatile.
L, a digesting furnace, having a circulatory vessel r, s, placed in it for extracting tinctures, &c.
N, O, P, three chimnies, which, after uniting, join the main chimney of the laboratory.

So, sand has been an indispensable material in the laboratory for a very long time indeed – 800 years of sand baths.

But if you google the term “sand bath” you will today come up with some bizarre images. I’ll avoid referring to the most bizarre, but here’s an example:

 

The supposed therapeutic qualities of hot sand, in particular black sand, continue to be exploited around the world, but nowhere to the degree of sophistication that the Japanese coastal resort of Beppu demonstrates. Blessed with many geothermal springs, bathhouses abound in Beppu, including the popular ones where you can pay to be buried in hot sand. You can see a video of the experience at http://www.japan-in-motion.com/jim/item/mov_243/, and http://www.hakusuikan.co.jp/en/spa/sand-bath.html declares (admittedly with some rather irritating background sounds) that “This Sand Bath in Ibusuki is very unusual throughout the entire world. Bury yourself in the sand comfortably, and have some snooze with a sound of the sea.... After burried in the sand, you can take a bath in big bathhouse, wash off the sand and refresh like... a baby!” It also shows a very convincing photo of blood before and after the treatment…

[For a great online tour of the Challenger expedition, see this Scripps Institution of Oceanography site; for the online documentation of the Challenger reports, see http://www.19thcenturyscience.org/HMSC/HMSC-INDEX/index-linked.htm and this French collection, easily navigable via the PDF titles.]

Comments

[Walter]

What amounts to a sand bath can be used to great advantage in a number of heat treating procedures in the technologically challenged metal working shop. It can provide an environment of otherwise expensive and difficult to achieve thermal inertia over a very useful range of temperatures.

[F]

Forgive me for asking, but have you been inspired by the same Connections Muse as James Burke? :) That was an amazing journey.

[Sandglass]

Of course I'll forgive you for asking - particularly since you've hit one proverbial nail on the head. The James Burke series has stuck in my head ever since I watched it. [Burke was a science historian whose series, "Connections" aired in the UK and the US in the late 70s; each one wove a story thread between scientific discoveries and related (although often seemingly unrelated) events]. It was, to my mind, one of the most compelling and fascinating documentary series ever. I guess that you identify with this view?

[F]

Indeed, I do identify with that view. The Connections 2 & 3 series were also excellent, produced in the mid nineties. James Burke also had a Connections column in Scientific American magazine for a while. (I have been a subscriber on and off for so long, I am not sure when the column was running.)

It is interesting to know that there is a connection there, if you will excuse the pun. But, connection or no, the knowledge and presentation styles exhibited both by you and by James Burke are excellent and admirable.

I love seeing the interrelatedness of seemingly disparate things, for informing the way I look at the world, and just for a good story.

I also thank Walter for his comment, and I would appreciate any pointers for looking into this. I found this an interesting application:
http://taogem.ganoksin.com/blogs/uncategorized/heat-treating-lapidary-cabochon-minerals-for-silver-solder-jewelry-design/
and was excited by a reference to tempering metals here:
http://www7.taosnet.com/ebear/metal/heattreat0.html
from a 1924 handbook, but all the links throw 404 errors, unfortunately.
Fluidized sand baths seem very interesting as well:
http://www.techneusa.com/tempcalibration/howdoflsdbathswork.htm

I'll just keep digging. Time, perhaps, to see what the local library system may have.

[Sandglass]

Thanks for the connections - and the compliments - you've spotted exactly what I humbly try to do.

Walter is an old friend and I've let him know about your comment, in case he hadn't seen it.

[Walter]

F: I'm afraid I have no idea where to look for anything that will help you with this. If I find anything, I'll post it here. I work as a blacksmith in a small shop. I've been at it for more than 30 years (wow) and am self-taught. Trial and error with emphasis on error. Also immense help from a number of books.

My work has been mainly ornamental, as opposed to technical, industrial, etc. The need to make, try, modify and recondition tools of various sorts arises frequently. This has led to the need to harden, temper, anneal and normalize various steels. Straight from my readings comes the practice of heating a piece of hardened steel above its upper critical temperature and burying it in the coal ashes to allow it to cool very slowly. In here, that passes for annealing.

On a number of occasions, I had difficulty tempering parts that were of varied section, i.e. thick and heavy in one part, light and narrow in another. The challenge was to heat the heavy part adequately and uniformly without overheating or over oxidizing the lighter parts. I find myself very hesitant to recommend some of the things I have tried. In the early days I learned two important lessons. The first was how to avoid getting burned. The second was that you're going to get burned anyway. Often. I've survived doing some fairly dangerous things. That doesn't make it OK. So read this, but DON"T DO IT.

The reference in the post was to a technique I have evolved (very crudely) in which I imbed a part to be tempered (temperatures ranging up to about 600 degrees [F]) in a bed of sand. The sand is contained in a cast iron pot or bowl and is preheated to desired temperature (as measured by oxidation colors on polished test strips). I have used my coal fire as a heat source. The advantage has been that the already hardened and brittle steel is not subjected to an abrupt temperature gradient. It can then sit there and soak at its temperature and cool very gradually. This has worked very well for me on a number of occasions. This description is quite abbreviated and I have tried a number of variants for differing requirements.

BTW: I share your enjoyment of Michael's posts and the James Burke approach to world view. I believe that the Scientific American column was mid to late nineties. I enjoyed all of Burke's series immensely. Good Luck!

[F]

Walter,

Thank you so much for sharing your experience with me. The likelihood that I should ever attempt such a thing is very remote, so no worries. I know what things like molten glass can do, and I respect their natures. (Incidentally, my woman was very nearly vapourized by molten Monofrax many years ago when the graphite mold was broken open too soon, so there is always that anecdotal scariness to remind me, should I ever happen to work with such hot substances.)

Again, I appreciate you taking the time to describe your usage of sand baths. I'll try to poke around a bit more, as I seem to remember (correctly or not) reading something on a similar technique used a bit further back in history, perhaps in China, for metallurgical or metalworking purposes. Perhaps I can find a copy of the handbook from 1924, a reference to which I had found at one of the links I posted previously.

Cheers,

Sean