The origin and use of bellows, especially in medieval Europe

I’m sure most of you are familiar with bellows, through seeing small, often ornate and decorative, sets of them by fireplaces. However the shape that they are today originated comparatively recently, becoming widespread in Europe in the medieval period.

The origin of bellows is well back in the prehistoric period, but they were made differently then. The first metal smelting, around the 6th millenium BC, that is, the 5,000’s BC, was done in draft and wind furnaces, that is like they fired pottery, and at that time or shortly after they realised they could smelt using blowpipes to introduce more oxygen. (http://www.persee.fr/web/revues/home/prescript/article/paleo_0153-9345_2000_num_26_2_4716)

Of course the problem is that this required lots of blowers to keep up the air rate, and the air ends up being damper and lower in oxygen because it has been through someone’s lungs. So someone invented bellows, or maybe several people invented them in different places at different times. Archaeologists have spent many backbreaking days operating bag bellows, made out of the skins of animals sewn together with a hole which can be opened and closed by movement of the fingers.

At the bottom of the bags are pipes called tuyères sticking out of the bottom, leading into the heart of the furnace. These are usually made of clay and sand or muck of some sort or another, so as to withstand the temperature of the fire, although the nozzles do tend to get fused and glassy. Finding them in an excavation is usually a good indication of a metal furnace, although a better one is finding the remains of the hearth itself, contaminated with traces of metal. People back then though did like to tidy up every little droplet of precious copper that they had.

It is a little hard to see what type of bellows are in this Old Egyptian wall painting:

http://www.reshafim.org.il/ad/egypt/trades/bronze_casting.htm

They look rather pot or more concertina like.

These are more efficient and easier to use. Still backbreaking work though.

Or perhaps they were more like this sort of iron age bellows:

http://www.davebudd.com/IronAgeBlacksmith.html

Scroll down to find photos of them in operation – essentially the leather sits as a lid on a pot, and has a hole in it which can be opened or closed, and the leather is pushed up and down.

As for the Greeks and Romans, it has proven remarkably hard to locate images of Hephaestus or Vulcan, the Roman equivalent. Those I can see tend to show him with a hammer and anvil, no sign of bellows.

The same fellow, Dave Budd, reckons that, http://www.davebudd.com/WoodlandWorkshop.html pot bellows were in use at this time, and also at some point kite bellows, although it is not clear from his photos exactly what they are. The internet turns up this:
http://paleometallurgy.blogspot.co.uk/2013/06/bronze-age-bellows-la-brenda-craddock.html

Which is a kits shaped bag bellow, which fits later descriptions apparently.

After the fall of Rome, obviously less evidence is available in Europe, but to judge by Theophilus’s work On Divers arts, the type of bellows in use in northern Europe in circa 1122 was still the comparatively primitive sort based on a bag, no different to those used in previous centuries. They were to be made this way:

“When the rams are killed, the skins should not be slit under the belly but opened from the rear and turned inside out so that they can be stripped off whole. (He tells you how to dry and cure them) Then tye should be greased and stretched againl. After this make a wooden head for the bellows to go through the neck and be tied there and make a hole in the head through which an iron pipe can go. Now, along the width of the bellows at the back, place four pieces of wood, which should be fitted to each other in pairs and tied together in the middle. Each pair should be sewn onto the bellows so that the places where they are joined are at the top and bottom of the middle [ of the opening of the skin]. At these points also two loops of the same skin should be sewn on, a smaller one at the top to hold the thumb and a larger one at the bottom for the four fingers.” (Page 83-84 of the Dover reprint)

This setup is for a small scale worker in metal. I’ve found online a 9th century AD illustration from the Stuttgart Psalter, via mention of it on a forum (f 121r):

http://www.bladesmithsforum.com/index.php?showtopic=20117

http://digital.wlb-stuttgart.de/sammlungen/sammlungsliste/werksansicht/?no_cache=1&tx_dlf%5Bid%5D=1343&tx_dlf%5Bpage%5D=249

Note that the two smiths are beavering away whilst Moses is coming down from the mountain and the others are worshipping a golden calf. It looks as if one advantage of this design of bellows is that you can operate the set with one hand whilst moving things about in the charcoal with the other.

Naturally there might be differences in technology between the UK and Germany, but really, given what was available and the communications of the period I think it unlikely that the UK was any more advanced in terms of bellows than Germany.

The earliest illustration of what we know of as bellows that I have found mention of is the Hylestad church carvings:

The church was estimated to have been built in the late 12th to early 13th century, and the illustration clearly shows a pair of single action bellows being used to run a smith’s forge. Note two tuyeres, one from each bellows, running into it.

So we have the modern sort in the late 12th/ early 13th century, compared to bag bellows circa 1122, which narrows it down nicely to about a century in which it seems the modern bellows were invented and spread about Europe. Perhaps rather rapidly as well, since illustrations abound from mid to late 13th century onwards:

http://visualiseur.bnf.fr/ConsulterElementNum?O=IFN-8007815&E=JPEG&Deb=1&Fin=1&Param=C

from 1250, courtesy of the Larsdatter links page. The problem there of course is that these are just the small set of handheld bellows you use at home. But at least next time you are blowing on a fire you can think of how old the design is, over 700 years.

This circa 1326 illustration is the oldest one Larsdatter has of the use of bellows on a forge:

http://classes.bnf.fr/ema/grands/ca001.htm

which makes it clear that the same design as for domestic use was in industrial use by this time.

Later illustrations are usually a bit clearer, and show better working too. For instance, the Holkham bible, English, circa 1327-1335, showing the same sort of bellows as we expect, so they were in use across Germany, France and England:

http://www.bl.uk/learning/images/medieval/year/large2163.html

You can clearly see that the illustrator has tried to draw a tiller to raise the bellows up and down alternately, but hasn’t succeeded. At least he drew the rope connecting the sticky out bits of the bellows to the pivoting piece of wood, and shows what are two rocks on top of the bellows, presumably to press them down and get a good blast of air out of them.

(As an aside, an ex-member of my re-enactment group had some bellows made, but didn’t have such handle like extensions on the end, claiming there was no evidence for them. Oddly enough most illustrations I have ever seen do show them, and without them it is much harder to operate the bellows, so I don’t know where he got his ideas from)

Also a couple of decent pictures here:

http://warehamforgeblog.blogspot.co.uk/2011/04/medieval-double-bag-bellows.html

A 15th century German illustration from the Mendel Hausbuch showing only one set, but that is often how they are badly drawn:

The advantage of using two sets of bellows is obvious. Arranged the way they are, one deflates whilst the other inflates, leading to a steady stream of air through the fire.

Several modern re-enactors have made such systems, such as this seen at Tatton:

Tatton 2007 pair of bellows and frame

And this at Kentwell, copying Bringucio’s “De Pyrotechnia”:

better rear view of Kentwell bellows

My own bronze casting setup at events is like this:

melting furnace Lanark 2010

I still need to make the proper rocking setup to make using them easier, and make a good strong stand for the bellows.

Meanwhile, domestic bellows continued to vary in shape, e.g. this 1520’s set:

http://bodley30.bodley.ox.ac.uk:8180/luna/servlet/detail/ODLodl~1~1~30984~107658:-The-Tudor-Pattern-Book-;jsessionid=F5E05BD40C4638C7904E80D6DBF78848?trs=3&mi=0&qvq=q%3Abucket%3Blc%3AODLodl~14~14%2CODLodl~1~1%2CODLodl~23~23%2CODLodl~24~24%2CODLodl~6~6%2CODLodl~7~7%2CODLodl~8~8

is distinctly rounder in shape than some earlier ones appear to be. But that was probably a matter of personal preference.

Another mystery to me at the moment is when double action action bellows were invented. They are the ones you can still see in historic blacksmiths. They have two sections, a top and bottom, with a hole between and a valve in it. The rope pulls up the bottom, which pushes air into the top section, which is pressed down upon by a weight. The advantage of these is the constant flow of air and the fact you can pump them up more than the older type, leaving them to deliver air for long enough that you can guddle about in the fire.

The earliest illustration I have seen so far is perhaps this:

Which dates from 1689.

Unfortunately you see them all the time at re-enactment events, even in the medieval period. But I can find no information on them before the 17th century, the problem being compounded by some potential confusion on wikipedia between double action piston and accordion bellows. I have certainly seen piston bellows in a late medieval picture:

And vertical accordion bellows seem to be a continental thing of the late medieval period, as you can see on the far left of this engraving:

But no sign of double action bellows, not in Biringuccio, (1540), Ercker (1580) mentions a pair of bellows, so obviously not single one, and I don’t have any more sources for later than that.

You can get instructions online to build them, and if you wanted a hand blown furnace I would make them.

On the other hand it is much easier to use this:

melting furnace with two airbed pumps

At the right you can see two small black air pumps powered by two 12v batteries, which deliver enough air to melt two or three hundred grams of metal in ten minutes. The photograph shows the furnace actually at 1100C in the hot part, but you can’t see the white hot area because the charcoal is in the way. It acts as insulation, helping keep the heat in.

Another option is a hairdryer, which would move much greater volumes of air, and they are frequently recomended in books about home foundry work, the problem being they need a 240v supply and you have to be wanting to melt a lot of metal, since if you put too much air through the charcoal you won’t get the best reactions and will blow some of the heat out.

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How not to make a stone mould for pewter spoons

Four years ago at Kentwell Hall I spent ages trying to make a stone mould for casting spoons in. It failed in a somewhat spectacular manner – I accidentally carved one side of the mould at the wrong angle, so the pewter ran out the bottom. An understanding of the shape required to make a spoon should make it clear why this would happen. soapstone spoon mould both sides Here are the two parts, on the left the male, the right the female with the indent for the bowl of the spoon. The male side has to fill the bowl, whilst leaving enough space for the metal to run between both sides. But I couldn’t see how to get both sides to match up perfectly when I was carving, and the result was as said. The white stuff in the photos is plaster, put there to try and block up the gap, but it didn’t work. This view from end on should make it clearer, the white plaster being on the right hand side: soapstone mould top view of male part You can see that the metal enters from the top of the bowl, and there are clear grooves cut to allow air out of the mould.

What I have just realised now, a few years too late, is that looking at the medieval stone mould pictured in this book:
http://books.google.co.uk/books?id=PDLPX7J8kW8C&lpg=PA144&vq=spoon&pg=PA66#v=snippet&q=spoon&f=false

, the bowl is sunk somewhat into the stone, i.e. the rim of the spoon is below the level of the upper face of the mould. This will firstly help give a good seal when the two parts are pressed together, and secondly might also allow room for manouvre in carving the bowl. Of course without the other half it is harder to be certain, but I think that indenting the female part and raising the male part above the level of the joining plane would perhaps make carving it a little easier. Ahh well. At least there is enough stone to spare that I can try to remake the mould and this time make a better job of it.