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26 Mar 2021

Time stands still

Written by Lauren Jackson, Conservator North
A close-up of a silver dial on a clock face. It features two circles, one numbered for minutes and the other for hours. It is engraved with the maker's name: Willm Hardy.
Silvered dial on the William Hardy longcase regulator at Fyvie Castle
How do you preserve a masterpiece of time? Find out more about how our conservation team protect the workings of one of the most complex machines before the 19th century.

In 2020 the COVID-19 pandemic swept across the world. Many countries were hurled into national lockdowns where individuals were unable to leave their homes except for essential reasons. A quiet descended as shops, restaurants and cafés closed; air travel was grounded; and roads became deserted. For many, time appeared to stand still.

The properties in the care of the National Trust for Scotland also stood quiet. With no visitors permitted to the majority of our sites, staff were furloughed and the only sounds left ringing were the clocks, who fell asleep on their last chime.

However, this was not the first occasion that time had stood still in the castles and houses of the National Trust for Scotland. In 2018 a generous donation allowed for a series of conservation works to commence on 19 longcase clocks housed in different properties across North East Scotland. One by one, the mechanisms have been carefully removed from their bespoke wooden casings and packaged, ready for transport to the ‘Clock Doctor’: Dr Christopher Edwards. He has been carrying out meticulous remedial works on these mechanisms, and this careful work continues today with one of the final clock mechanisms now receiving care.

The workings

For thousands of years, devices have been used to measure and track time – from hourglasses, candle clocks, water clocks and sundials, to modern-day battery-powered digital clocks, phones and laptops. The first mechanical clock was conceived in the early part of the 14th century and, until the 19th century, the clock was one of the most sophisticated mechanisms in the world. A mechanical clock is composed of a movement/mechanism, a dial showing the time, and a case housing these parts. The movement is made up of a series of toothed wheels and pinions (gears) set between plates, which are held together with pillars.

The wheels, pinions and plates would have been made from iron or steel in early clocks, but in the 16th century brass became the standard material used. The clock is powered either by a ‘weight-driven’ movement (weights attached to a line wound around a barrel) or by a ‘spring-driven’ movement (the release of a coiled spring contained in a barrel).

A close-up of a clock mechanism, showing a large outer cogged wheel, with a smaller one screwed on top.
The winding barrel from the William Hardy longcase regulator at Fyvie Castle

The movement is regulated by an escapement, which controls the transfer of the power from the weights or the spring. It’s called the escapement as it allows one tooth of a wheel to escape at a time. The earliest form of escapement was shaped like a crown and known as a verge escapement. The earliest domestic clocks in the 14th century would have used verge escapements but were often poor timekeepers as they were based on the principle of balanced weights. These weights would shift during movement, causing the crown wheel in the verge escapement to turn faster or slower. Consequently, the hand on the dial turned faster or slower, resulting in the clock losing or gaining up to 15 minutes a day.

A line illustration diagram, with labels, that shows how a verge escapement works in a clock. It shows a structure with a weight balanced either side and a cogged wheel in the middle.
A diagram depicting the workings of a verge escapement

Evolution of the clock

In 1583 Galileo discovered the isochronism (a movement that occurs at equal intervals) of the pendulum, which became the turning point for more accurate mechanical clocks in the 17th century. Galileo himself never managed to apply this precise movement to the measurement of time, but in 1656 the Dutch scientist Christiaan Huygens applied Galileo’s findings and invented the pendulum clock. It improved the daily timekeeping of a clock from a deviance of 15 minutes to just a couple of minutes. Early pendulum clocks still had some variance in their timekeeping due to the use of the verge escapement mechanism, which allowed wide swings of the pendulum.

The British scientist Robert Hooke advanced Huygens’ work, improving the accuracy of the verge escapement by engineering a recoil anchor escapement. Named because it resembles a ship’s anchor, the anchor escapement essentially acts as a mechanical linkage, turning a toothed cog/wheel to provide a small push to every swing the pendulum takes. It also controls the length of the swing by catching the tooth of the cog on the return swing, creating much smaller swinging arcs to those of pendulum clocks with a verge escapement. The anchor escapement prevents the pendulum from slowing down, whilst also moving the hands of the clock forward at a steady rate, providing more accurate timekeeping and the recognisable ‘tick, tock’ sound.

Thanks to the preciseness of the anchor escapement, the English clockmaker William Clement refined Hooke’s mechanism. He found that, through employing longer and heavier pendulums, he could produce a pendulum swing that lasted precisely one second. This exciting find in 1670 allowed Clement to design a clock so accurate that it would vary no more than 10 seconds per day. The mechanism was housed inside a case alongside its 39-inch long pendulum – Clement had created the first longcase clock.

Development of the longcase clock

The ‘long case’ is thought to have been created simply as protection for the pendulum and weights, which hang below the movement housed within the dial and hood. The cases were mainly produced in wood by cabinet makers and therefore reflect different styles during the 17th and 18th centuries. The earlier cases were very simple in style, but more elaborate cases later became popular, with intricate marquetry and parquetry designs; some even had the addition of a glass window in the trunk door to reveal the swinging pendulum. In the early 18th century taller longcases (up to 2.5m) became popular. Examples of these early towering clocks by prominent clockmakers Hugh Gordon and Thomas Stones can be seen in Haddo House, Leith Hall and Castle Fraser. Lacquer and Japanned finishes were also common, reflecting the interest in Chinese and Japanese art later in the 18th century – Brodie Castle is lucky to have a fine example of such a case.

A longcase clock stands against a plain grey wall at the foot of some stairs. It stands on a red and white patterned rug. Its wooden case is highly polished and decorated with patterns and an image of a ship and a saintly woman. There are elaborate bronze finials on top of the clock.
Eight-day japanned longcase clock (signed Robert Clisdale, Edinburgh) at Brodie Castle, c1760–65

The designs on the hood and the dials of the longcase clocks also varied over time with changes in trends. The earliest dials were made from brass and were typically square in shape; some would also be engraved with elaborate designs. The break arch dial would often feature the maker’s name or a rolling moon and became popular after c1715. In the late 18th century silvered dials appeared with decorative ormolu finishes, whilst painted clock dials with decorative floral swags and artistic scenes became more popular in the 19th century. Two examples at the House of Dun demonstrate the variety of these dials.

Mechanisms were further developed during the 18th century in order to achieve greater accuracy. Most notably, the deadbeat anchor escapement was invented by George Graham c1715, which featured the same anchor linkage but with two curved pallets at its tip rather than straight pallets. This prevented recoil when each tooth of the escape wheel locked and released with the pallets. Graham also invented the mercurial pendulum in 1726, a glass vial filled with mercury as the bob (weight) on the end of a steel rod. This compensated for the timekeeping inaccuracies of the traditional brass and lead pendulums caused by temperature fluctuations that resulted in expansion and contraction, altering the pendulums’ length and swing. The gridiron pendulum was also invented c1726 by John Harrison for the same purpose, to ensure the uniform length of the pendulum (and therefore a consistent swing) for accurate timekeeping. These longcase clocks became known as regulators as they were accurate to within 10 seconds per month.

Many longcase clocks became heirlooms and were passed down through generations and housed in different properties, so it’s not uncommon to find the feet or finials removed, crest-work on the hood cut down or converted, and other alterations as clocks were made to fit within specific interiors. Mechanisms and dials were also sometimes removed from their original cases and combined with sections from another longcase clock – this was known as a ‘marriage’.

Deterioration and conservation

With the introduction of the longcase clock and its accurate timekeeping, owners of great houses and castles could ensure the more precise day-to-day running of the household. From the late 17th century many prominent families introduced this ‘timekeeper’ into their homes. Although we have much more advanced appliances to tell the time today, these modern devices would look out of place in our historic interiors and would not offer the same ambience. The ‘tick tock’ of the original working clocks brings historic houses and castles to life. As with all other collections housed within Trust properties, appropriate care and consideration is taken before running any of the historical clocks. The rate of deterioration to the mechanism of a functioning clock increases with use, so a carefully balanced approach is required. All mechanisms are assessed to ensure they are in an appropriate condition.

Deterioration of these intricate mechanisms is often due to a number of factors, including usage, poor environment, gaseous pollution, pests, historic repairs and adaptions.

Usage

The mechanisms of most clocks are incredibly delicate. Through the integral driving force and momentum in the movement, delicate sections of the design will endure mechanical stress, making them vulnerable to damage through metal fatigue. Poor craftsmanship, materials and construction can increase the natural fragility in these mechanisms. Handling and over-winding of mechanisms can also place the internal components under extreme stresses and forces, which can result in fatigue failures.

Poor environment

High relative humidity (RH) can have a detrimental effect to the metal components of the clock’s mechanism, causing rust and corrosion. Low RH and high temperatures can also cause damage, by causing the lubricating oils in the mechanism to dry out. When a combination of dust and particulate pollution adheres to the oil, the oil can become thick and acidic, acting more like a ‘grinding paste’, which can cause etching to the metal and possible seizure of the clock.

Pests

Clock cases are often favoured by insects as a home. Spiders create webs in the mechanism, which attract dust and other particulates, becoming problematic for the movement. Other insects like furniture beetle can cause damage to the cases as their larvae bore through the wood and weaken the structure.

Historic repairs and adaptions

Repairs were often made to ensure the continued functioning of a clock, but some of these historical repairs have inadvertently caused further damage to the mechanisms, due to the methods, materials and cleaning solutions used or replacement parts fitted. Polishing of the silver dials has sometimes led to the silver being polished off. Painted dials have suffered from crude overpainting. Marriages of different clock parts have led to internal scoring, with parts not fitting correctly and/or sections being removed and lost. Brute-force repairs have caused metal fatigue and breakages. Incorrect materials used to replace parts or patch sections, such as lead solder, adhesive resins and plastic replacements, often put other sections under undue pressure and stress. Incorrect cleaning solutions have left residues, accelerating corrosion.

We’re fortunate that the selected longcase clock mechanisms were in a condition that allowed for remedial conservation to make them operational again. This meticulous work has involved the careful disassembly of the mechanisms; inspection of all parts; cleaning and removal of dust, debris, congealed oil and corrosion; repairs to worn parts; and delicate re-assembly and re-lubrication with new oil. Further work has been carried out on some of our longcase clocks, including replacement of failing gut lines; re-silvering of dials where they have been over-polished; remedial repairs to the wooden veneers, skirting and mouldings on the cases; as well as repairs to broken or bent dial hands. This work will need to be repeated every few years if we continue to operate these clocks. Like all working machinery, they require regular ‘servicing’ and ‘health checks’.

The restoration of the Hugh Gordon longcase clock at Leith Hall

Transcript

Hello and welcome to the overhaul of this Hugh Gordon longcase. Hugh Gordon of Aberdeen, dating from about 1770 from Leith Hall.

The first thing to do is to take the dial and the hands off, and I can then start to strip down the movement.
Without being cleaned, then you’re going to get a build-up of dirty oil, dust and so on.
With every piece that’s taken off, you examine it just to see that there’s any damage.
This has got a date on it – 1983 – and that may be the last time this clock was ever overhauled, so it’s really past its time.
A grandfather clock like this should be cleaned every 8-10 years, or thereabouts. As well as cleaning the movement, I would also clean the seatboard. And this would have been the original seatboard when the clock was made 200-and-odd years ago.

You can see all the individual parts in the box together, and although the two barrels look the same, they are in fact perhaps slightly different. In this instance, they have been marked with a small ‘s’ and a small ‘w’, which stands for ‘watch’ and ‘strike’. The watch being the clock part, and the strike obviously is the strike side – so those are the two barrels.

Now, taking one wheel at a time, and a device knows as a burnisher, and if there’s not too much or not any significant wear that could be detected on the pivot, then all you would have to do would be to burnish this pivot and just by rotating it to burnish the pivot, so that it’s a very high polish. And that gives you the best bearing surface, and the same would apply to the other end, to the … this is where the seconds hand fits. And the idea is to remove any very, very slight imperfections in the pivot itself.
And you can see the pivot end here, just with the burnisher for scale, and you can see how highly polished that pivot end is. The pinion itself – this is the small steel gear – it has got minor amounts of bright spots on some of the pinion leaves, and this is where one of the wheels has been meshing with that, but that’s … that would be normal wear and tear. And in this instance, there’s no problems with that.

I’ve started rebushing this hole here, knocking out the existing bush – that’s what was there – but it was too big for the pivot, and eventually I will flatten this off, you can see it’s still quite raised, and that’s now got to be flat.
So I hope you can now see that the bush has now been made as flat as the plate. So next thing to do is to test that wheel in its hole. The hole has been opened up, but we’ll test it between the plates – put the two plates together and make sure it runs satisfactorily. If it doesn’t, then a little bit more adjustment has got to be done.
See if the wheel’s spinning freely between the plates and coming to a stop gradually rather than coming to a jerk. Perfect.
So we’ll just check it when it’s horizontal, so … well, that all looks very good.

One of the more important things to check when doing an overhaul on our longcase clock, or any clock for that matter, is the drop – the so-called drop – or the geometry, really, of the pallets. So we have the escape wheel and the pallets. And this is the part of the clock where you hear the tick. You can see that as the pallets rock backwards and forwards, and that’s dictated … the speed of that happening is dictated, of course, by the pendulum swing – the pendulum is the time keeper, really. And what you’re looking for is how much movement there is as each tooth passes through this device.
Here we go. That’s going through quite nicely.

So, this is the longcase movement, partially assembled. All the wheels are now in position. This wheel here is the pinwheel, which causes … as this rotates, so the hammer gets lifted. This is the hammer, so that would be lifted by this lever here. The pinwheel will rotate as the weight drags the barrel down, so this barrel is meshed with this wheel, and this wheel will rotate. And so, all the wheels are now in place, and the only thing to do now is to put the top plate on, or the front plate, really.

Every part has been examined – has been cleaned – and then the final thing to do is to hand polish it with a chalk brush. And this gets the final pieces of corrosion or of discolouration off the brass.
You might also notice there’s no finger marks anywhere on the clock, so the whole thing is assembled either with tweezers, like this, or with a piece of cloth. So you’re not handling the brass at all, because brass … although it’s a metal, it’s actually quite a soft metal, and it will tarnish, particularly with the touching it with fingerprints – leaving fingerprints.

So, that’s the front plate now on. Eventually, the minute hand will go on here. The calendar, the rack, the detent, the lifting piece, the reverse minute wheel – this is the seconds hand here, and this is the gathering pallet arbour there.
This is part of the hour wheel. This part I have brushed with the chalk brush, and this part I haven’t. So by just rubbing the brush on a piece of chalk – this is just normal white chalk – and brushing it, it just removes the final, sort of, dark staining.
This is the part where the hour hand fits. This is the snail, which is the device which dictates how many times the clock strikes.
That’s the hour wheel all in place. But before that can go on, we have to put on the bridge.

So now to start the, sort of, reassembly of the movement on the front plate, I’m going to put on the minute wheel and the bridge. And then the tension washer, which allows you to turn the hands, that goes underneath the minute wheel. And then the minute wheel, which interestingly has a small dot, and that allows you to set up the clock with the reverse minute wheel accurately, so that the hour hand and the minute hand all kind of mesh together correctly. Likewise, the bridge, which goes on top of this, has a punch mark there … a punch depression. And there’s another punch mark on the plate there, so I’ll put that on.

There are several elements to the striking. We have the rack – this toothed sector here – and at the end of that, fixed rigidly to it, is the rack tail. And each step of the snail is deeper than the next, and there are 12 steps.
And as the clock turns, so this wheel here – the reverse minute wheel, which is geared directly to the minute wheel immediately behind the big wheel – it turns, and this pin comes round and starts to lift this lever. So that lifts slowly, slowly, slowly. And you can see what happens. Everything is starting to run – I don’t know if you can hear that – it’s starting to run, and then stop. And as that pin finally gets round far enough for that lever to drop, the clock will strike. And the number of times it strikes is dictated by how many teeth get to that position as the rack drops.
And that is dictated by the snail, and it has 12 steps on it. And there’s a pin on the end of the rack tail here. And as the rack gets lifted, so that pin hits the edge of the snail.
Now, it’s crucial that the length of this arm here, and the spacing between each of these teeth, are consistent, because the length of that and the length of that are fixed points.
If the rack tail gets broken, then there’s a degree of expertise required to determine what length that should be, relative to the length of that, because of the spacing on the rack teeth.
That’s rack and snail striking.

The Trust has been able to preserve these historically significant mechanisms thanks to the generosity of donors, members and visitors. We would particularly like to note the generosity of Miss Jean Mackenzie, who donated in order that these historically significant mechanisms could be preserved. Miss Mackenzie sadly passed away shortly after making her donation to the Trust. We hope, however, that she found pleasure in knowing that her support would safeguard this important collection for the nation, so more moments in time can be shared and enjoyed.

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