Time stands still

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).

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.

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.

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 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.