g'day chris here and welcome back to clickspring
in episode 4 of the main build series I raised the issue of how the ancients may
have increased the visibility of layout lines whilst making components for the
mechanism and you recall that I tried out candle sort as one possible idea now
there were many excellent ideas suggested in the comments of that video
so in this video I'm going to test out a few of those ideas to see what else
might have plausibly been used the mechanism was constructed almost
entirely from a lote in bronze so I've chosen a similar alloy for these test
pieces and a lot of the ideas could be broadly categorized as being oxide based
making use of the natural tendency for bronze to form a dark patina over time
in fact it could be argued that no enhancement of the surface would have
been required at all the metal would likely have had an oxide coating from
the formation process and it does provide a reasonable contrast but I've
discovered through the construction process that abrasives almost certainly
played a large role in the fabrication of the machine particularly in achieving
the very tight clearances so that would almost certainly have been situations
when layout lines were placed on to freshly abraded metal surfaces and so
would have benefited from some sort of contrast enhancement so with that being
the case there are a lot of excellent ideas that essentially involved forcing
the rapid formation of oxide onto a fresh surface the first of which is
simple heating
and it certainly works well I used a butane torch for convenience and almost
any heat source from the period would have done the job it's a tough oxide and
the contrast is good so a heat generated oxide is a definite possibility but
there are also many ways to chemically generate an oxide using readily
available chemicals from the period ammonia and vinegar are two strong
candidates and I found the best results by simply exposing the test pieces to
the vapor of each chemical
the result with vinegar was certainly clear but the ammonia was by far the
most effective of the two generating a deep green patina within a few hours of
exposure it's also possible that the apps more complex chemicals were created
from the more common ingredients this ammonium sulfate solution was easy
enough to make and generated a very clean oxide layer in a matter of minutes
and while it's not entirely clear that liver of sulfur was now and during the
period it does seem to be a reasonable proxy for the various sulfur based
compounds that likely would have been available and again it generates a clear
useful result
so with several plausible methods chemical oxidation of the metal surface
would have been a relatively convenient way to improve the law in contrast
although it's worth pointing out that some might have been more practical than
others ammonia for example produces a very tough green oxide but it does
appear to come at the cost of a small amount of the surface metal a similar
issue applies to vinegar it's a decent oxide but it rubs off relatively easily
and the reaction has lightly pitted the surface the ammonium sulfate oxide is
excellent very tough and uniform at the cost of essentially no metal and the
same applies to liver of sulfur it's a very tough oxide and with an excellent
contrast now I guess that each of these methods present a small liability in the
shop with regard to the smell of the chemicals and the risk of spillage but
they're certainly workable particularly the last two it would have been fairly
straightforward to remove the oxide with an abrasive such as powdered pumice and
it's easy to imagine this last step that he worked into the general build process
of setting clearances as a given part approach completion now another
suggestion for chemically altering the surface of the metal revolves around
using blue stone solution otherwise known as copper sulfate in addition to
being well suited to growing large crystals copper sulfate solution reacts
easily with the surface of ferrous metals depositing a thin layer of
metallic copper onto the metal surface
it's a very convenient and effective method for improving line contrast and
can be easily removed with a light abrasive but the problem is that copper
sulfate doesn't react with copper based alloys such as bronze so although it was
an to some extent still is used as a marking fluid for ferrous metals it
wouldn't have been applicable to the construction of the bronze components of
this particular mechanism now before I move on to some of the other ideas I'd
like to quickly revisit the idea of suit and lampblack simple candle sort proved
to be a little too fragile to a large extent that fragility comes down to the
fuel that was burned some fuels generate an oilier soot that more readily sticks
to the surface and it's clear that paraffin also known as kerosene is one
of those fuels and for that reason it's still in use today
it deposits a velvet black coating onto the surface of the metal that while it
can still be easily rubbed off is durable enough for a modest amount of
marking and handling however it's not clear that paraffin was necessarily
available in the region during the period of the mechanisms construction so
to keep the technique in play we need a fuel from the period that
provides a similar result s Fulton is known to have been widely used in
antiquity for various sealing tasks and so is worth considering and while it
certainly burns well it generates a suit that's reminiscent of candle wax coming
off with very little handling so on its own burning asphaltum is not that
effective at a lower based soot also fits well within the period in terms of
availability of materials and is easily formed into a candle for convenient
application
but again it's very fragile and probably the least persistent of the suits that I
tested coming away from the surface of the metal with the slightest touch
fortunately though there is one candidate that stands out and that's
olive oil it was of course widely available in the region and as it
happens generates a very oily suit that's almost indistinguishable from
that made by paraffin so for an ancient candidate for simply smoking the part I
think it's hard to go past olive oil now asphalt amor pitch can be used directly
on the metal but one very interesting suggestion involves combining asphaltum
with some other ancient ingredients to form a hard specialized wax
once cool the wax is Finley smeared onto the pre-warmed part and initially
doesn't look to be at all promising but the application of suit completely
transforms it into something that's quite impressive
to show you what a difference the wax makes I've suited the other side of the
test piece without it and of course the straight tallow suit comes off as easily
as before but the side with the wax has formed a very robust coating that has a
relatively hard plastic feel it takes a scriber mark easily and importantly
aside from providing excellent contrast it also has the other main property of
equality marking material and that's the ability to take a mark without
necessarily requiring that the underlying metal be scored now this
isn't something that all marking methods can provide so it really sets this one
apart is very suitable for complex marking tasks that require a lot of
surface construction lines that you'd rather not have to remove later with
abrasives add the fact that it can be removed with hot water and I think this
one really stands out as a solid candidate okay so the next collection of
suggestions can be broadly described as an easily applied binding material
combined with some sort of pigment in solution and a good example of this of
course is the modern layer fluid a reasonable approximation of which can be
made by combining gentian violet with denatured alcohol and shellac resin
now gentian violet is a distinctly modern compound so clearly this specific
combination is not consistent with the period with the obvious performance of
the modern fluid naturally leads to the question was there an ancient equivalent
that preceded it shellac and other resins like for example colophony was
certainly widely known and used during the period and if applied in a thin coat
with a suitable pigment would likely be a reasonable candidate but there's a bit
of a problem whilst these resins do dissolve readily in pure alcohol they're
largely insoluble in other common liquids of the period like for example
water wine or vinegar and alcohol distillation is presently understood to
come much later in the historical record
now other solvents are certainly possible so I wouldn't necessarily write
the idea of entirely and the resins can be applied reasonably thinly with
nothing more than heat but the solvent issue does complicate things a little in
any event there are a great many other pigment based IDs that can't easily fit
the bill without much issue about a suitable solvent and we should probably
cover the most popular one first good Eve now I have to admit I wasn't overly
keen on being the donor for this particular test but there's never a
volunteer around when you need one so here it is some of my own limited supply
aside from supply issues though there are some other drawbacks to consider it
does take a reasonable time to dry and it severely affects ferrous materials
although we can ignore that for our purpose given that we're only concerned
with the effect on bronze which appears to be relatively modest on the plus side
it takes a line excellently and again has that property of enabling marking of
the coating rather than the metal underneath it's very robust to handling
and of course water soluble so supply issues aside blood definitely checks out
another very popular idea was squid ink and I'd have to say that overall it's a
good candidate it seems likely that it would have been readily available in the
period and it provides a decent contrast with the underlying metal although it
did prove to be a little uneven during application and the longer drawing time
would certainly have been a drawback but one surprise was that it generated a
particularly tough coating yet being water-soluble was also very easy to
remove both attributes that strongly recommended a clay slurry would
certainly have been cheap to source and easy to apply so on first inspection
would also seem to be a reasonable candidate with an acceptable drying time
it initially appears to hold a line well but the coating is quite soft and not
well bonded to the underlying surface so it quickly becomes apparent that it
can't tolerate much in the way of handling a water-based paint like for
example Chinese white is certainly a possibility it's quick to dry very
tolerant to handling and holds a line well and no doubt these are the
attributes that keep it in use today by some hand engravers
but it must be said that it doesn't provide a great contrast with the
underlying metal and that does raise the question is there perhaps something
similar from the period that would have provided a better contrast the elite
purple dye of the period is even today I watering lis expensive so I think we can
rule that one out but there were many other affordable
dyes available like for example Road an excellent source of natural indigo dye
it's a plant-based diet and is easily mixed into a thin suspension and then
applied to the work
drying time is acceptable and it does take a line quite well although it's not
quite as robust to handling as for example China white or blood
now not the possibility to consider is a pigment added to some sort of tempera
paint base again I used wowed as the indigo sauce with egg yolk for the base
I wouldn't say that it was the best material to apply and I'm not sure how
long it could be stored also the drying time was a little impractical but other
than that the results were very impressive the markings were clear and
it proved to be one of the materials most tolerant to handling
there were many suggestions based around other plant-based coloring materials
like for example wine berry extracts and juices I tried out both wine and
beetroot juice and discovered that there was an issue common to both each looked
quite promising going onto the surface but they simply never drive instead
forming a sticky residue on the surface now it's possible that this could be
improved with various additives so I wouldn't necessarily rule this one out
but it does complicate it as an option
one of my favorites of the whole testing process was India ink this stuff really
is fascinating to make and use and much like the mechanism itself has its
origins thousands of years in the past
it's also an excellent example of what's known as a colloidal suspension where an
otherwise insoluble material in this case lampblack remain suspended in
another substance
now it's probably a little impractical due to the drying time but even so it's
a worthy candidate for the job it's easy to apply and takes the mark well and was
probably the most durable of all tested materials to handling it again came off
very easily with only water the lampblack component of India ink can
also be combined with some sort of non water-based binding agent like for
example beeswax
combined over a medium heat the lampblack easily goes into suspension in
the wax and can then be applied to a pre warmed part
it does take the line well but it has to be said that's a little soft and so
easily smudged which brings us to the final and perhaps simplest idea of all
and that is to score the metal directly and then rubbing some sort of wax or
coating so that only the lines themselves show up a technique that's
generally referred to as smudge marking now this might not always be an
acceptable approach it's never fun to have to remove deep construction lines
on the surface of the work at the end of a project but for some situations it
would have been hard to go past such an effective idea so there you have it a
bunch of possible solutions that could have been used independently or maybe
even together depending on the job at hand this test piece for the engraving
of the rear dial is a good example when it comes to the actual work piece of
probably used smudge marking for keeping track of the arcs and engraving the
radial lines but I can easily imagine that the maker would have preferred to
see the general layout of the text before pulling out the hammer and chisel
and getting stuck in say something that works a little more like a modern
marking fluid would probably have been desirable a material that could take the
marking while also permitting some small Corrections and that would also hold up
to a lot of hand contact from the engraving process
for this test I tried out the asfalt and gum mastic and beeswax mix and I have to
say it's suited the job well the text was still readable throughout the job
despite a lot of hand contact and pressure and the coating came off easily
with hot water it even helped with the overall visibility of the engraving by
lightly colouring the inside of the cuts and making them stand out a little more
clearly against the surrounding metal now that's not to say that one of the
other options might not work even better so I'll continue to test out various
ideas over the coming videos and be sure to let me know which methods you think
of worth testing out further in the comments below thanks for watching I'll
see ya later
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