g'day chris here and welcome back to clickspring I'm in the process of
fastening the curbs to the main plate of the Antikythera mechanism these are the
curved metal strips that help to stabilize the larger rotating assemblies
three underneath the main solar drive wheel were held in place with pins but
the remainder were held in place with soft solder the scan of one join in
particular shows the full extent of what was achievable at the time a thin layer
of solder that is for the most part run quite well throughout the join and it
tells us a great deal because although the tools and materials may have evolved
the requirements for a good solder joint were exactly the same 2,000 years ago as
they are today above all the joint surfaces must have
been clean of contaminants a flux of some description was used to allow the
solder to wet the metal surface the joint was fabricated to be closed to
allow the capillary force to draw the liquid solder inside and for the solder
to flow easily the part of the surrounding area must have been raised
to a temperature somewhat above the solder melting point now the main plate
of the mechanism is a substantial heatsink and for the most part the
components are unrestrained and so easily knocked out of position so it's
clear that the maker had a means of applying substantial heat to a specific
work area that also permitted gentle application of the solder and the
challenge is to achieve the same result using the tools and materials known to
have existed at the time so starting with the heat source the ancients had
considerable experience working copper and well understood its properties so I
think it's likely that the hot tools were indeed made from copper and in all
likelihood resembles what we were described as an old-school soldering
iron the solder may well have been applied using the tip of the bit but the
nature of the parts suggests to me that the bits were probably just the heat
source and that the solder was more likely touched into the join from the
side so after a bit of testing I've settled on a collection of old-style
copper bits along with some larger copper blocks
the smaller bits allow me to more precisely direct the heat where it's
needed and I've made them quite long and narrow to reach down inside the small
gaps between the blocks the blocks are larger and so act as a broader heat
source to raise the temperature of the general work area they can also be left
cold and so act as a heat sink to protect a part that's already been
soldered into position now I've mentioned in previous videos that I
think abrasives played a big role in the construction of the mechanism in this
case I'm using powdered pumice on a damp cloth to reveal fresh metal but it's not
enough to simply clean off the surface and leave it at that
as the metal is heated oxides quickly reform on the surface and work to repel
the solder it sits on top of the oxide layer as a sort of paste and now a man
of heat will make it flow on the metal underneath so in addition to being clean
a flux is required to chemically reduce the oxide and allow the metal to wet the
surface and there are two types of flux to consider passive and active the
classic active flux is a dilute zinc chloride solution formed from
hydrochloric acid and zinc otherwise known as killed spirits now the use of
killed spirits can be traced back many hundreds of years and so today we
consider it to be quite traditional but I've yet to find a source establishing
its use as far back as antiquity so despite it being an excellent flux for
now I'm leaving it out of contention of the passive fluxes tallow is well
documented as being used in the period but I think the more likely contender is
rosin otherwise known as Greek pitch or by its regional name of colophony
rosin would have been readily available during the period of the mechanisms
construction and it's a superbly effective flux still in widespread use
today it also has the benefit that it's easy to work with and control with the
gentle heat it can be manipulated into a convenient shape for ready application
to the work area and the last material to consider is of
course the solder now we don't know the exact composition of the alloy used in
the mechanism but the radio dense nature of the join suggests a lead-based solder
and I think a 60/40 10 led alloy is a reasonable starting point again the
charcoal fire can be used to heat the raw components until molten and it's
easily solidified into conveniently held shapes for later use ok so that's
everything required time to give it a go and see how it all performs I'm using a
naturally aspirated charcoal fire to heat the tools and the first thing to
mention is just how labor-intensive and resource hungry it is it takes a lot of
time and charcoal to get the tools to the required temperature and it takes a
fair amount of work to keep the fire well tended and hot of course the heat
immediately starts to leave the tools as soon as they're removed from the coals
so I found I needed to work fairly quickly to get the best results and also
that planning the sequence of events was important everything needs to be close
to hand to keep the process flowing and make the best use of the heat for the
larger pieces it also helped to break the job into two parts first by heating
up the plate enough to flow the rosin and then dropping the part into its
general position at this elevated temperature the rosin stays tacky for a
few minutes allowing a more careful positioning of the part after which the
hot tools were returned to run the solder into the join
now there's no doubt that this is a very different way of working compared to the
modern process but for all the differences
it's the similarities that are the most striking because no matter the tools or
methods used it all still comes down to seeing that tiny flash of silver as the
solder runs around the scene indicating a good join somewhere in the distant
past either by accident or design someone saw that flash of silver and
recognized its potential the process of how to best make it happen was mastered
and then passed on until it eventually became part of the workshop tradition
that led to not just the Antikythera mechanism but also much of the
technology that followed it so that even now thousands of years later soft solder
remains one of the easiest and most common methods for joining metal thanks
for watching I'll see you later